rfc6830
Internet Engineering Task Force (IETF) D. Farinacci
Request for Comments: 6830 Cisco Systems
Category: Experimental V. Fuller
ISSN: 2070-1721
D. Meyer
D. Lewis
Cisco Systems
January 2013
The Locator/ID Separation Protocol (LISP)
Abstract
This document describes a network-layer-based protocol that enables
separation of IP addresses into two new numbering spaces: Endpoint
Identifiers (EIDs) and Routing Locators (RLOCs). No changes are
required to either host protocol stacks or to the "core" of the
Internet infrastructure. The Locator/ID Separation Protocol (LISP)
can be incrementally deployed, without a "flag day", and offers
Traffic Engineering, multihoming, and mobility benefits to early
adopters, even when there are relatively few LISP-capable sites.
Design and development of LISP was largely motivated by the problem
statement produced by the October 2006 IAB Routing and Addressing
Workshop.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for examination, experimental implementation, and
evaluation.
This document defines an Experimental Protocol for the Internet
community. This document is a product of the Internet Engineering
Task Force (IETF). It represents the consensus of the IETF
community. It has received public review and has been approved for
publication by the Internet Engineering Steering Group (IESG). Not
all documents approved by the IESG are a candidate for any level of
Internet Standard; see Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6830.
Farinacci, et al. Experimental [Page 1]
RFC 6830 LISP January 2013
Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction ....................................................3
2. Requirements Notation ...........................................5
3. Definition of Terms .............................................5
4. Basic Overview .................................................10
4.1. Packet Flow Sequence ......................................13
5. LISP Encapsulation Details .....................................15
5.1. LISP IPv4-in-IPv4 Header Format ...........................16
5.2. LISP IPv6-in-IPv6 Header Format ...........................17
5.3. Tunnel Header Field Descriptions ..........................18
5.4. Dealing with Large Encapsulated Packets ...................22
5.4.1. A Stateless Solution to MTU Handling ...............22
5.4.2. A Stateful Solution to MTU Handling ................23
5.5. Using Virtualization and Segmentation with LISP ...........24
6. EID-to-RLOC Mapping ............................................25
6.1. LISP IPv4 and IPv6 Control-Plane Packet Formats ...........25
6.1.1. LISP Packet Type Allocations .......................27
6.1.2. Map-Request Message Format .........................27
6.1.3. EID-to-RLOC UDP Map-Request Message ................30
6.1.4. Map-Reply Message Format ...........................31
6.1.5. EID-to-RLOC UDP Map-Reply Message ..................35
6.1.6. Map-Register Message Format ........................37
6.1.7. Map-Notify Message Format ..........................39
6.1.8. Encapsulated Control Message Format ................41
6.2. Routing Locator Selection .................................42
6.3. Routing Locator Reachability ..............................44
6.3.1. Echo Nonce Algorithm ...............................46
6.3.2. RLOC-Probing Algorithm .............................48
6.4. EID Reachability within a LISP Site .......................49
6.5. Routing Locator Hashing ...................................49
Farinacci, et al. Experimental [Page 2]
RFC 6830 LISP January 2013
6.6. Changing the Contents of EID-to-RLOC Mappings .............50
6.6.1. Clock Sweep ........................................51
6.6.2. Solicit-Map-Request (SMR) ..........................52
6.6.3. Database Map-Versioning ............................53
7. Router Performance Considerations ..............................54
8. Deployment Scenarios ...........................................55
8.1. First-Hop/Last-Hop Tunnel Routers .........................56
8.2. Border/Edge Tunnel Routers ................................56
8.3. ISP Provider Edge (PE) Tunnel Routers .....................57
8.4. LISP Functionality with Conventional NATs .................58
8.5. Packets Egressing a LISP Site .............................58
9. Traceroute Considerations ......................................58
9.1. IPv6 Traceroute ...........................................59
9.2. IPv4 Traceroute ...........................................60
9.3. Traceroute Using Mixed Locators ...........................60
10. Mobility Considerations .......................................61
10.1. Site Mobility ............................................61
10.2. Slow Endpoint Mobility ...................................61
10.3. Fast Endpoint Mobility ...................................61
10.4. Fast Network Mobility ....................................63
10.5. LISP Mobile Node Mobility ................................64
11. Multicast Considerations ......................................64
12. Security Considerations .......................................65
13. Network Management Considerations .............................67
14. IANA Considerations ...........................................67
14.1. LISP ACT and Flag Fields .................................67
14.2. LISP Address Type Codes ..................................68
14.3. LISP UDP Port Numbers ....................................68
14.4. LISP Key ID Numbers ......................................68
15. Known Open Issues and Areas of Future Work ....................68
16. References ....................................................70
16.1. Normative References .....................................70
16.2. Informative References ...................................71
Appendix A. Acknowledgments .......................................74
1. Introduction
This document describes the Locator/Identifier Separation Protocol
(LISP), which provides a set of functions for routers to exchange
information used to map from Endpoint Identifiers (EIDs) that are not
globally routable to routable Routing Locators (RLOCs). It also
defines a mechanism for these LISP routers to encapsulate IP packets
addressed with EIDs for transmission across a network infrastructure
that uses RLOCs for routing and forwarding.
Farinacci, et al. Experimental [Page 3]
RFC 6830 LISP January 2013
Creation of LISP was initially motivated by discussions during the
IAB-sponsored Routing and Addressing Workshop held in Amsterdam in
October 2006 (see [RFC4984]). A key conclusion of the workshop was
that the Internet routing and addressing system was not scaling well
in the face of the explosive growth of new sites; one reason for this
poor scaling is the increasing number of multihomed sites and other
sites that cannot be addressed as part of topology-based or provider-
based aggregated prefixes. Additional work that more completely
describes the problem statement may be found in [RADIR].
A basic observation, made many years ago in early networking research
such as that documented in [CHIAPPA] and [RFC4984], is that using a
single address field for both identifying a device and for
determining where it is topologically located in the network requires
optimization along two conflicting axes: for routing to be efficient,
the address must be assigned topologically; for collections of
devices to be easily and effectively managed, without the need for
renumbering in response to topological change (such as that caused by
adding or removing attachment points to the network or by mobility
events), the address must explicitly not be tied to the topology.
The approach that LISP takes to solving the routing scalability
problem is to replace IP addresses with two new types of numbers:
Routing Locators (RLOCs), which are topologically assigned to network
attachment points (and are therefore amenable to aggregation) and
used for routing and forwarding of packets through the network; and
Endpoint Identifiers (EIDs), which are assigned independently from
the network topology, are used for numbering devices, and are
aggregated along administrative boundaries. LISP then defines
functions for mapping between the two numbering spaces and for
encapsulating traffic originated by devices using non-routable EIDs
for transport across a network infrastructure that routes and
forwards using RLOCs. Both RLOCs and EIDs are syntactically
identical to IP addresses; it is the semantics of how they are used
that differs.
This document describes the protocol that implements these functions.
The database that stores the mappings between EIDs and RLOCs is
explicitly a separate "module" to facilitate experimentation with a
variety of approaches. One database design that is being developed
for experimentation as part of the LISP working group work is
[RFC6836]. Others that have been described include [CONS], [EMACS],
and [RFC6837]. Finally, [RFC6833] documents a general-purpose
service interface for accessing a mapping database; this interface is
intended to make the mapping database modular so that different
approaches can be tried without the need to modify installed LISP-
capable devices in LISP sites.
Farinacci, et al. Experimental [Page 4]
RFC 6830 LISP January 2013
This experimental specification has areas that require additional
experience and measurement. It is NOT RECOMMENDED for deployment
beyond experimental situations. Results of experimentation may lead
to modifications and enhancements of protocol mechanisms defined in
this document. See Section 15 for specific, known issues that are in
need of further work during development, implementation, and
experimentation.
An examination of the implications of LISP on Internet traffic,
applications, routers, and security is for future study. This
analysis will explain what role LISP can play in scalable routing and
will also look at scalability and levels of state required for
encapsulation, decapsulation, liveness, and so on.
2. Requirements Notation
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
3. Definition of Terms
Provider-Independent (PI) Addresses: PI addresses are an address
block assigned from a pool where blocks are not associated with
any particular location in the network (e.g., from a particular
service provider) and are therefore not topologically aggregatable
in the routing system.
Provider-Assigned (PA) Addresses: PA addresses are an address block
assigned to a site by each service provider to which a site
connects. Typically, each block is a sub-block of a service
provider Classless Inter-Domain Routing (CIDR) [RFC4632] block and
is aggregated into the larger block before being advertised into
the global Internet. Traditionally, IP multihoming has been
implemented by each multihomed site acquiring its own globally
visible prefix. LISP uses only topologically assigned and
aggregatable address blocks for RLOCs, eliminating this
demonstrably non-scalable practice.
Routing Locator (RLOC): An RLOC is an IPv4 [RFC0791] or IPv6
[RFC2460] address of an Egress Tunnel Router (ETR). An RLOC is
the output of an EID-to-RLOC mapping lookup. An EID maps to one
or more RLOCs. Typically, RLOCs are numbered from topologically
aggregatable blocks that are assigned to a site at each point to
which it attaches to the global Internet; where the topology is
defined by the connectivity of provider networks, RLOCs can be
thought of as PA addresses. Multiple RLOCs can be assigned to the
same ETR device or to multiple ETR devices at a site.
Farinacci, et al. Experimental [Page 5]
RFC 6830 LISP January 2013
Endpoint ID (EID): An EID is a 32-bit (for IPv4) or 128-bit (for
IPv6) value used in the source and destination address fields of
the first (most inner) LISP header of a packet. The host obtains
a destination EID the same way it obtains a destination address
today, for example, through a Domain Name System (DNS) [RFC1034]
lookup or Session Initiation Protocol (SIP) [RFC3261] exchange.
The source EID is obtained via existing mechanisms used to set a
host's "local" IP address. An EID used on the public Internet
must have the same properties as any other IP address used in that
manner; this means, among other things, that it must be globally
unique. An EID is allocated to a host from an EID-Prefix block
associated with the site where the host is located. An EID can be
used by a host to refer to other hosts. EIDs MUST NOT be used as
LISP RLOCs. Note that EID blocks MAY be assigned in a
hierarchical manner, independent of the network topology, to
facilitate scaling of the mapping database. In addition, an EID
block assigned to a site may have site-local structure
(subnetting) for routing within the site; this structure is not
visible to the global routing system. In theory, the bit string
that represents an EID for one device can represent an RLOC for a
different device. As the architecture is realized, if a given bit
string is both an RLOC and an EID, it must refer to the same
entity in both cases. When used in discussions with other
Locator/ID separation proposals, a LISP EID will be called an
"LEID". Throughout this document, any references to "EID" refer
to an LEID.
EID-Prefix: An EID-Prefix is a power-of-two block of EIDs that are
allocated to a site by an address allocation authority.
EID-Prefixes are associated with a set of RLOC addresses that make
up a "database mapping". EID-Prefix allocations can be broken up
into smaller blocks when an RLOC set is to be associated with the
larger EID-Prefix block. A globally routed address block (whether
PI or PA) is not inherently an EID-Prefix. A globally routed
address block MAY be used by its assignee as an EID block. The
converse is not supported. That is, a site that receives an
explicitly allocated EID-Prefix may not use that EID-Prefix as a
globally routed prefix. This would require coordination and
cooperation with the entities managing the mapping infrastructure.
Once this has been done, that block could be removed from the
globally routed IP system, if other suitable transition and access
mechanisms are in place. Discussion of such transition and access
mechanisms can be found in [RFC6832] and [LISP-DEPLOY].
Farinacci, et al. Experimental [Page 6]
RFC 6830 LISP January 2013
End-system: An end-system is an IPv4 or IPv6 device that originates
packets with a single IPv4 or IPv6 header. The end-system
supplies an EID value for the destination address field of the IP
header when communicating globally (i.e., outside of its routing
domain). An end-system can be a host computer, a switch or router
device, or any network appliance.
Ingress Tunnel Router (ITR): An ITR is a router that resides in a
LISP site. Packets sent by sources inside of the LISP site to
destinations outside of the site are candidates for encapsulation
by the ITR. The ITR treats the IP destination address as an EID
and performs an EID-to-RLOC mapping lookup. The router then
prepends an "outer" IP header with one of its globally routable
RLOCs in the source address field and the result of the mapping
lookup in the destination address field. Note that this
destination RLOC MAY be an intermediate, proxy device that has
better knowledge of the EID-to-RLOC mapping closer to the
destination EID. In general, an ITR receives IP packets from site
end-systems on one side and sends LISP-encapsulated IP packets
toward the Internet on the other side.
Specifically, when a service provider prepends a LISP header for
Traffic Engineering purposes, the router that does this is also
regarded as an ITR. The outer RLOC the ISP ITR uses can be based
on the outer destination address (the originating ITR's supplied
RLOC) or the inner destination address (the originating host's
supplied EID).
TE-ITR: A TE-ITR is an ITR that is deployed in a service provider
network that prepends an additional LISP header for Traffic
Engineering purposes.
Egress Tunnel Router (ETR): An ETR is a router that accepts an IP
packet where the destination address in the "outer" IP header is
one of its own RLOCs. The router strips the "outer" header and
forwards the packet based on the next IP header found. In
general, an ETR receives LISP-encapsulated IP packets from the
Internet on one side and sends decapsulated IP packets to site
end-systems on the other side. ETR functionality does not have to
be limited to a router device. A server host can be the endpoint
of a LISP tunnel as well.
TE-ETR: A TE-ETR is an ETR that is deployed in a service provider
network that strips an outer LISP header for Traffic Engineering
purposes.
Farinacci, et al. Experimental [Page 7]
RFC 6830 LISP January 2013
xTR: An xTR is a reference to an ITR or ETR when direction of data
flow is not part of the context description. "xTR" refers to the
router that is the tunnel endpoint and is used synonymously with
the term "Tunnel Router". For example, "An xTR can be located at
the Customer Edge (CE) router" indicates both ITR and ETR
functionality at the CE router.
LISP Router: A LISP router is a router that performs the functions
of any or all of the following: ITR, ETR, Proxy-ITR (PITR), or
Proxy-ETR (PETR).
EID-to-RLOC Cache: The EID-to-RLOC Cache is a short-lived,
on-demand table in an ITR that stores, tracks, and is responsible
for timing out and otherwise validating EID-to-RLOC mappings.
This cache is distinct from the full "database" of EID-to-RLOC
mappings; it is dynamic, local to the ITR(s), and relatively
small, while the database is distributed, relatively static, and
much more global in scope.
EID-to-RLOC Database: The EID-to-RLOC Database is a global
distributed database that contains all known EID-Prefix-to-RLOC
mappings. Each potential ETR typically contains a small piece of
the database: the EID-to-RLOC mappings for the EID-Prefixes
"behind" the router. These map to one of the router's own
globally visible IP addresses. The same database mapping entries
MUST be configured on all ETRs for a given site. In a steady
state, the EID-Prefixes for the site and the Locator-Set for each
EID-Prefix MUST be the same on all ETRs. Procedures to enforce
and/or verify this are outside the scope of this document. Note
that there MAY be transient conditions when the EID-Prefix for the
site and Locator-Set for each EID-Prefix may not be the same on
all ETRs. This has no negative implications, since a partial set
of Locators can be used.
Recursive Tunneling: Recursive Tunneling occurs when a packet has
more than one LISP IP header. Additional layers of tunneling MAY
be employed to implement Traffic Engineering or other re-routing
as needed. When this is done, an additional "outer" LISP header
is added, and the original RLOCs are preserved in the "inner"
header. Any references to tunnels in this specification refer to
dynamic encapsulating tunnels; they are never statically
configured.
Re-encapsulating Tunnels: Re-encapsulating Tunneling occurs when an
ETR removes a LISP header, then acts as an ITR to prepend another
LISP header. Doing this allows a packet to be re-routed by the
re-encapsulating router without adding the overhead of additional
tunnel headers. Any references to tunnels in this specification
Farinacci, et al. Experimental [Page 8]
RFC 6830 LISP January 2013
refer to dynamic encapsulating tunnels; they are never statically
configured. When using multiple mapping database systems, care
must be taken to not create re-encapsulation loops through
misconfiguration.
LISP Header: LISP header is a term used in this document to refer
to the outer IPv4 or IPv6 header, a UDP header, and a LISP-
specific 8-octet header that follow the UDP header and that an ITR
prepends or an ETR strips.
Address Family Identifier (AFI): AFI is a term used to describe an
address encoding in a packet. An address family currently
pertains to an IPv4 or IPv6 address. See [AFI] and [RFC3232] for
details. An AFI value of 0 used in this specification indicates
an unspecified encoded address where the length of the address is
0 octets following the 16-bit AFI value of 0.
Negative Mapping Entry: A negative mapping entry, also known as a
negative cache entry, is an EID-to-RLOC entry where an EID-Prefix
is advertised or stored with no RLOCs. That is, the Locator-Set
for the EID-to-RLOC entry is empty or has an encoded Locator count
of 0. This type of entry could be used to describe a prefix from
a non-LISP site, which is explicitly not in the mapping database.
There are a set of well-defined actions that are encoded in a
Negative Map-Reply (Section 6.1.5).
Data-Probe: A Data-Probe is a LISP-encapsulated data packet where
the inner-header destination address equals the outer-header
destination address used to trigger a Map-Reply by a decapsulating
ETR. In addition, the original packet is decapsulated and
delivered to the destination host if the destination EID is in the
EID-Prefix range configured on the ETR. Otherwise, the packet is
discarded. A Data-Probe is used in some of the mapping database
designs to "probe" or request a Map-Reply from an ETR; in other
cases, Map-Requests are used. See each mapping database design
for details. When using Data-Probes, by sending Map-Requests on
the underlying routing system, EID-Prefixes must be advertised.
However, this is discouraged if the core is to scale by having
less EID-Prefixes stored in the core router's routing tables.
Proxy-ITR (PITR): A PITR is defined and described in [RFC6832]. A
PITR acts like an ITR but does so on behalf of non-LISP sites that
send packets to destinations at LISP sites.
Proxy-ETR (PETR): A PETR is defined and described in [RFC6832]. A
PETR acts like an ETR but does so on behalf of LISP sites that
send packets to destinations at non-LISP sites.
Farinacci, et al. Experimental [Page 9]
RFC 6830 LISP January 2013
Route-returnability: Route-returnability is an assumption that the
underlying routing system will deliver packets to the destination.
When combined with a nonce that is provided by a sender and
returned by a receiver, this limits off-path data insertion. A
route-returnability check is verified when a message is sent with
a nonce, another message is returned with the same nonce, and the
destination of the original message appears as the source of the
returned message.
LISP site: LISP site is a set of routers in an edge network that are
under a single technical administration. LISP routers that reside
in the edge network are the demarcation points to separate the
edge network from the core network.
Client-side: Client-side is a term used in this document to indicate
a connection initiation attempt by an EID. The ITR(s) at the LISP
site are the first to get involved in obtaining database Map-Cache
entries by sending Map-Request messages.
Server-side: Server-side is a term used in this document to indicate
that a connection initiation attempt is being accepted for a
destination EID. The ETR(s) at the destination LISP site are the
first to send Map-Replies to the source site initiating the
connection. The ETR(s) at this destination site can obtain
mappings by gleaning information from Map-Requests, Data-Probes,
or encapsulated packets.
Locator-Status-Bits (LSBs): Locator-Status-Bits are present in the
LISP header. They are used by ITRs to inform ETRs about the up/
down status of all ETRs at the local site. These bits are used as
a hint to convey up/down router status and not path reachability
status. The LSBs can be verified by use of one of the Locator
reachability algorithms described in Section 6.3.
Anycast Address: Anycast Address is a term used in this document to
refer to the same IPv4 or IPv6 address configured and used on
multiple systems at the same time. An EID or RLOC can be an
anycast address in each of their own address spaces.
4. Basic Overview
One key concept of LISP is that end-systems (hosts) operate the same
way they do today. The IP addresses that hosts use for tracking
sockets and connections, and for sending and receiving packets, do
not change. In LISP terminology, these IP addresses are called
Endpoint Identifiers (EIDs).
Farinacci, et al. Experimental [Page 10]
RFC 6830 LISP January 2013
Routers continue to forward packets based on IP destination
addresses. When a packet is LISP encapsulated, these addresses are
referred to as Routing Locators (RLOCs). Most routers along a path
between two hosts will not change; they continue to perform routing/
forwarding lookups on the destination addresses. For routers between
the source host and the ITR as well as routers from the ETR to the
destination host, the destination address is an EID. For the routers
between the ITR and the ETR, the destination address is an RLOC.
Another key LISP concept is the "Tunnel Router". A Tunnel Router
prepends LISP headers on host-originated packets and strips them
prior to final delivery to their destination. The IP addresses in
this "outer header" are RLOCs. During end-to-end packet exchange
between two Internet hosts, an ITR prepends a new LISP header to each
packet, and an ETR strips the new header. The ITR performs
EID-to-RLOC lookups to determine the routing path to the ETR, which
has the RLOC as one of its IP addresses.
Some basic rules governing LISP are:
o End-systems (hosts) only send to addresses that are EIDs. They
don't know that addresses are EIDs versus RLOCs but assume that
packets get to their intended destinations. In a system where
LISP is deployed, LISP routers intercept EID-addressed packets and
assist in delivering them across the network core where EIDs
cannot be routed. The procedure a host uses to send IP packets
does not change.
o EIDs are always IP addresses assigned to hosts.
o LISP routers mostly deal with Routing Locator addresses. See
details in Section 4.1 to clarify what is meant by "mostly".
o RLOCs are always IP addresses assigned to routers, preferably
topologically oriented addresses from provider CIDR (Classless
Inter-Domain Routing) blocks.
o When a router originates packets, it may use as a source address
either an EID or RLOC. When acting as a host (e.g., when
terminating a transport session such as Secure SHell (SSH),
TELNET, or the Simple Network Management Protocol (SNMP)), it may
use an EID that is explicitly assigned for that purpose. An EID
that identifies the router as a host MUST NOT be used as an RLOC;
an EID is only routable within the scope of a site. A typical BGP
configuration might demonstrate this "hybrid" EID/RLOC usage where
a router could use its "host-like" EID to terminate iBGP sessions
to other routers in a site while at the same time using RLOCs to
terminate eBGP sessions to routers outside the site.
Farinacci, et al. Experimental [Page 11]
RFC 6830 LISP January 2013
o Packets with EIDs in them are not expected to be delivered
end-to-end in the absence of an EID-to-RLOC mapping operation.
They are expected to be used locally for intra-site communication
or to be encapsulated for inter-site communication.
o EID-Prefixes are likely to be hierarchically assigned in a manner
that is optimized for administrative convenience and to facilitate
scaling of the EID-to-RLOC mapping database. The hierarchy is
based on an address allocation hierarchy that is independent of
the network topology.
o EIDs may also be structured (subnetted) in a manner suitable for
local routing within an Autonomous System (AS).
An additional LISP header MAY be prepended to packets by a TE-ITR
when re-routing of the path for a packet is desired. A potential
use-case for this would be an ISP router that needs to perform
Traffic Engineering for packets flowing through its network. In such
a situation, termed "Recursive Tunneling", an ISP transit acts as an
additional ITR, and the RLOC it uses for the new prepended header
would be either a TE-ETR within the ISP (along an intra-ISP traffic
engineered path) or a TE-ETR within another ISP (an inter-ISP traffic
engineered path, where an agreement to build such a path exists).
In order to avoid excessive packet overhead as well as possible
encapsulation loops, this document mandates that a maximum of two
LISP headers can be prepended to a packet. For initial LISP
deployments, it is assumed that two headers is sufficient, where the
first prepended header is used at a site for Location/Identity
separation and the second prepended header is used inside a service
provider for Traffic Engineering purposes.
Tunnel Routers can be placed fairly flexibly in a multi-AS topology.
For example, the ITR for a particular end-to-end packet exchange
might be the first-hop or default router within a site for the source
host. Similarly, the ETR might be the last-hop router directly
connected to the destination host. Another example, perhaps for a
VPN service outsourced to an ISP by a site, the ITR could be the
site's border router at the service provider attachment point.
Mixing and matching of site-operated, ISP-operated, and other Tunnel
Routers is allowed for maximum flexibility. See Section 8 for more
details.
Farinacci, et al. Experimental [Page 12]
RFC 6830 LISP January 2013
4.1. Packet Flow Sequence
This section provides an example of the unicast packet flow with the
following conditions:
o Source host "host1.abc.example.com" is sending a packet to
"host2.xyz.example.com", exactly what host1 would do if the site
was not using LISP.
o Each site is multihomed, so each Tunnel Router has an address
(RLOC) assigned from the service provider address block for each
provider to which that particular Tunnel Router is attached.
o The ITR(s) and ETR(s) are directly connected to the source and
destination, respectively, but the source and destination can be
located anywhere in the LISP site.
o Map-Requests can be sent on the underlying routing system
topology, to a mapping database system, or directly over an
Alternative Logical Topology [RFC6836]. A Map-Request is sent for
an external destination when the destination is not found in the
forwarding table or matches a default route.
o Map-Replies are sent on the underlying routing system topology.
Client host1.abc.example.com wants to communicate with server
host2.xyz.example.com:
1. host1.abc.example.com wants to open a TCP connection to
host2.xyz.example.com. It does a DNS lookup on
host2.xyz.example.com. An A/AAAA record is returned. This
address is the destination EID. The locally assigned address of
host1.abc.example.com is used as the source EID. An IPv4 or IPv6
packet is built and forwarded through the LISP site as a normal
IP packet until it reaches a LISP ITR.
2. The LISP ITR must be able to map the destination EID to an RLOC
of one of the ETRs at the destination site. The specific method
used to do this is not described in this example. See [RFC6836]
or [CONS] for possible solutions.
3. The ITR will send a LISP Map-Request. Map-Requests SHOULD be
rate-limited.
Farinacci, et al. Experimental [Page 13]
RFC 6830 LISP January 2013
4. When an alternate mapping system is not in use, the Map-Request
packet is routed through the underlying routing system.
Otherwise, the Map-Request packet is routed on an alternate
logical topology, for example, the [RFC6836] database mapping
system. In either case, when the Map-Request arrives at one of
the ETRs at the destination site, it will process the packet as a
control message.
5. The ETR looks at the destination EID of the Map-Request and
matches it against the prefixes in the ETR's configured
EID-to-RLOC mapping database. This is the list of EID-Prefixes
the ETR is supporting for the site it resides in. If there is no
match, the Map-Request is dropped. Otherwise, a LISP Map-Reply
is returned to the ITR.
6. The ITR receives the Map-Reply message, parses the message (to
check for format validity), and stores the mapping information
from the packet. This information is stored in the ITR's
EID-to-RLOC mapping cache. Note that the map-cache is an
on-demand cache. An ITR will manage its map-cache in such a way
that optimizes for its resource constraints.
7. Subsequent packets from host1.abc.example.com to
host2.xyz.example.com will have a LISP header prepended by the
ITR using the appropriate RLOC as the LISP header destination
address learned from the ETR. Note that the packet MAY be sent
to a different ETR than the one that returned the Map-Reply due
to the source site's hashing policy or the destination site's
Locator-Set policy.
8. The ETR receives these packets directly (since the destination
address is one of its assigned IP addresses), checks the validity
of the addresses, strips the LISP header, and forwards packets to
the attached destination host.
In order to defer the need for a mapping lookup in the reverse
direction, an ETR MAY create a cache entry that maps the source EID
(inner-header source IP address) to the source RLOC (outer-header
source IP address) in a received LISP packet. Such a cache entry is
termed a "gleaned" mapping and only contains a single RLOC for the
EID in question. More complete information about additional RLOCs
SHOULD be verified by sending a LISP Map-Request for that EID. Both
the ITR and the ETR may also influence the decision the other makes
in selecting an RLOC. See Section 6 for more details.
Farinacci, et al. Experimental [Page 14]
RFC 6830 LISP January 2013
5. LISP Encapsulation Details
Since additional tunnel headers are prepended, the packet becomes
larger and can exceed the MTU of any link traversed from the ITR to
the ETR. It is RECOMMENDED in IPv4 that packets do not get
fragmented as they are encapsulated by the ITR. Instead, the packet
is dropped and an ICMP Too Big message is returned to the source.
This specification RECOMMENDS that implementations provide support
for one of the proposed fragmentation and reassembly schemes. Two
existing schemes are detailed in Section 5.4.
Since IPv4 or IPv6 addresses can be either EIDs or RLOCs, the LISP
architecture supports IPv4 EIDs with IPv6 RLOCs (where the inner
header is in IPv4 packet format and the outer header is in IPv6
packet format) or IPv6 EIDs with IPv4 RLOCs (where the inner header
is in IPv6 packet format and the outer header is in IPv4 packet
format). The next sub-sections illustrate packet formats for the
homogeneous case (IPv4-in-IPv4 and IPv6-in-IPv6), but all 4
combinations MUST be supported.
Farinacci, et al. Experimental [Page 15]
RFC 6830 LISP January 2013
5.1. LISP IPv4-in-IPv4 Header Format
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ |Version| IHL |Type of Service| Total Length |
/ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Identification |Flags| Fragment Offset |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
OH | Time to Live | Protocol = 17 | Header Checksum |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Source Routing Locator |
\ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ | Destination Routing Locator |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ | Source Port = xxxx | Dest Port = 4341 |
UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ | UDP Length | UDP Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
L |N|L|E|V|I|flags| Nonce/Map-Version |
I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
S / | Instance ID/Locator-Status-Bits |
P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ |Version| IHL |Type of Service| Total Length |
/ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Identification |Flags| Fragment Offset |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IH | Time to Live | Protocol | Header Checksum |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Source EID |
\ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ | Destination EID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IHL = IP-Header-Length
Farinacci, et al. Experimental [Page 16]
RFC 6830 LISP January 2013
5.2. LISP IPv6-in-IPv6 Header Format
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ |Version| Traffic Class | Flow Label |
/ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Payload Length | Next Header=17| Hop Limit |
v +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
O + +
u | |
t + Source Routing Locator +
e | |
r + +
| |
H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
d | |
r + +
| |
^ + Destination Routing Locator +
| | |
\ + +
\ | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ | Source Port = xxxx | Dest Port = 4341 |
UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ | UDP Length | UDP Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
L |N|L|E|V|I|flags| Nonce/Map-Version |
I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
S / | Instance ID/Locator-Status-Bits |
P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ |Version| Traffic Class | Flow Label |
/ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ | Payload Length | Next Header | Hop Limit |
v +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Farinacci, et al. Experimental [Page 17]
RFC 6830 LISP January 2013
| |
I + +
n | |
n + Source EID +
e | |
r + +
| |
H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
d | |
r + +
| |
^ + Destination EID +
\ | |
\ + +
\ | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
5.3. Tunnel Header Field Descriptions
Inner Header (IH): The inner header is the header on the datagram
received from the originating host. The source and destination IP
addresses are EIDs [RFC0791] [RFC2460].
Outer Header: (OH) The outer header is a new header prepended by an
ITR. The address fields contain RLOCs obtained from the ingress
router's EID-to-RLOC Cache. The IP protocol number is "UDP (17)"
from [RFC0768]. The setting of the Don't Fragment (DF) bit
'Flags' field is according to rules listed in Sections 5.4.1 and
5.4.2.
UDP Header: The UDP header contains an ITR selected source port when
encapsulating a packet. See Section 6.5 for details on the hash
algorithm used to select a source port based on the 5-tuple of the
inner header. The destination port MUST be set to the well-known
IANA-assigned port value 4341.
UDP Checksum: The 'UDP Checksum' field SHOULD be transmitted as zero
by an ITR for either IPv4 [RFC0768] or IPv6 encapsulation
[UDP-TUNNELS] [UDP-ZERO]. When a packet with a zero UDP checksum
is received by an ETR, the ETR MUST accept the packet for
decapsulation. When an ITR transmits a non-zero value for the UDP
checksum, it MUST send a correctly computed value in this field.
When an ETR receives a packet with a non-zero UDP checksum, it MAY
choose to verify the checksum value. If it chooses to perform
such verification, and the verification fails, the packet MUST be
silently dropped. If the ETR chooses not to perform the
verification, or performs the verification successfully, the
packet MUST be accepted for decapsulation. The handling of UDP
Farinacci, et al. Experimental [Page 18]
RFC 6830 LISP January 2013
checksums for all tunneling protocols, including LISP, is under
active discussion within the IETF. When that discussion
concludes, any necessary changes will be made to align LISP with
the outcome of the broader discussion.
UDP Length: The 'UDP Length' field is set for an IPv4-encapsulated
packet to be the sum of the inner-header IPv4 Total Length plus
the UDP and LISP header lengths. For an IPv6-encapsulated packet,
the 'UDP Length' field is the sum of the inner-header IPv6 Payload
Length, the size of the IPv6 header (40 octets), and the size of
the UDP and LISP headers.
N: The N-bit is the nonce-present bit. When this bit is set to 1,
the low-order 24 bits of the first 32 bits of the LISP header
contain a Nonce. See Section 6.3.1 for details. Both N- and
V-bits MUST NOT be set in the same packet. If they are, a
decapsulating ETR MUST treat the 'Nonce/Map-Version' field as
having a Nonce value present.
L: The L-bit is the 'Locator-Status-Bits' field enabled bit. When
this bit is set to 1, the Locator-Status-Bits in the second
32 bits of the LISP header are in use.
x 1 x x 0 x x x
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|N|L|E|V|I|flags| Nonce/Map-Version |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Locator-Status-Bits |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
E: The E-bit is the echo-nonce-request bit. This bit MUST be ignored
and has no meaning when the N-bit is set to 0. When the N-bit is
set to 1 and this bit is set to 1, an ITR is requesting that the
nonce value in the 'Nonce' field be echoed back in LISP-
encapsulated packets when the ITR is also an ETR. See
Section 6.3.1 for details.
V: The V-bit is the Map-Version present bit. When this bit is set to
1, the N-bit MUST be 0. Refer to Section 6.6.3 for more details.
This bit indicates that the LISP header is encoded in this
case as:
0 x 0 1 x x x x
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|N|L|E|V|I|flags| Source Map-Version | Dest Map-Version |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Instance ID/Locator-Status-Bits |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Farinacci, et al. Experimental [Page 19]
RFC 6830 LISP January 2013
I: The I-bit is the Instance ID bit. See Section 5.5 for more
details. When this bit is set to 1, the 'Locator-Status-Bits'
field is reduced to 8 bits and the high-order 24 bits are used as
an Instance ID. If the L-bit is set to 0, then the low-order
8 bits are transmitted as zero and ignored on receipt. The format
of the LISP header would look like this:
x x x x 1 x x x
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|N|L|E|V|I|flags| Nonce/Map-Version |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Instance ID | LSBs |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
flags: The 'flags' field is a 3-bit field reserved for future flag
use. It MUST be set to 0 on transmit and MUST be ignored on
receipt.
LISP Nonce: The LISP 'Nonce' field is a 24-bit value that is
randomly generated by an ITR when the N-bit is set to 1. Nonce
generation algorithms are an implementation matter but are
required to generate different nonces when sending to different
destinations. However, the same nonce can be used for a period of
time to the same destination. The nonce is also used when the
E-bit is set to request the nonce value to be echoed by the other
side when packets are returned. When the E-bit is clear but the
N-bit is set, a remote ITR is either echoing a previously
requested echo-nonce or providing a random nonce. See
Section 6.3.1 for more details.
LISP Locator-Status-Bits (LSBs): When the L-bit is also set, the
'Locator-Status-Bits' field in the LISP header is set by an ITR to
indicate to an ETR the up/down status of the Locators in the
source site. Each RLOC in a Map-Reply is assigned an ordinal
value from 0 to n-1 (when there are n RLOCs in a mapping entry).
The Locator-Status-Bits are numbered from 0 to n-1 from the least
significant bit of the field. The field is 32 bits when the I-bit
is set to 0 and is 8 bits when the I-bit is set to 1. When a
Locator-Status-Bit is set to 1, the ITR is indicating to the ETR
that the RLOC associated with the bit ordinal has up status. See
Section 6.3 for details on how an ITR can determine the status of
the ETRs at the same site. When a site has multiple EID-Prefixes
that result in multiple mappings (where each could have a
different Locator-Set), the Locator-Status-Bits setting in an
encapsulated packet MUST reflect the mapping for the EID-Prefix
that the inner-header source EID address matches. If the LSB for
an anycast Locator is set to 1, then there is at least one RLOC
with that address, and the ETR is considered 'up'.
Farinacci, et al. Experimental [Page 20]
RFC 6830 LISP January 2013
When doing ITR/PITR encapsulation:
o The outer-header 'Time to Live' field (or 'Hop Limit' field, in
the case of IPv6) SHOULD be copied from the inner-header 'Time to
Live' field.
o The outer-header 'Type of Service' field (or the 'Traffic Class'
field, in the case of IPv6) SHOULD be copied from the inner-header
'Type of Service' field (with one exception; see below).
When doing ETR/PETR decapsulation:
o The inner-header 'Time to Live' field (or 'Hop Limit' field, in
the case of IPv6) SHOULD be copied from the outer-header 'Time to
Live' field, when the Time to Live value of the outer header is
less than the Time to Live value of the inner header. Failing to
perform this check can cause the Time to Live of the inner header
to increment across encapsulation/decapsulation cycles. This
check is also performed when doing initial encapsulation, when a
packet comes to an ITR or PITR destined for a LISP site.
o The inner-header 'Type of Service' field (or the 'Traffic Class'
field, in the case of IPv6) SHOULD be copied from the outer-header
'Type of Service' field (with one exception; see below).
Note that if an ETR/PETR is also an ITR/PITR and chooses to
re-encapsulate after decapsulating, the net effect of this is that
the new outer header will carry the same Time to Live as the old
outer header minus 1.
Copying the Time to Live (TTL) serves two purposes: first, it
preserves the distance the host intended the packet to travel;
second, and more importantly, it provides for suppression of looping
packets in the event there is a loop of concatenated tunnels due to
misconfiguration. See Section 9.3 for TTL exception handling for
traceroute packets.
The Explicit Congestion Notification ('ECN') field occupies bits 6
and 7 of both the IPv4 'Type of Service' field and the IPv6 'Traffic
Class' field [RFC3168]. The 'ECN' field requires special treatment
in order to avoid discarding indications of congestion [RFC3168].
ITR encapsulation MUST copy the 2-bit 'ECN' field from the inner
header to the outer header. Re-encapsulation MUST copy the 2-bit
'ECN' field from the stripped outer header to the new outer header.
If the 'ECN' field contains a congestion indication codepoint (the
value is '11', the Congestion Experienced (CE) codepoint), then ETR
decapsulation MUST copy the 2-bit 'ECN' field from the stripped outer
header to the surviving inner header that is used to forward the
Farinacci, et al. Experimental [Page 21]
RFC 6830 LISP January 2013
packet beyond the ETR. These requirements preserve CE indications
when a packet that uses ECN traverses a LISP tunnel and becomes
marked with a CE indication due to congestion between the tunnel
endpoints.
5.4. Dealing with Large Encapsulated Packets
This section proposes two mechanisms to deal with packets that exceed
the path MTU between the ITR and ETR.
It is left to the implementor to decide if the stateless or stateful
mechanism should be implemented. Both or neither can be used, since
it is a local decision in the ITR regarding how to deal with MTU
issues, and sites can interoperate with differing mechanisms.
Both stateless and stateful mechanisms also apply to Re-encapsulating
and Recursive Tunneling, so any actions below referring to an ITR
also apply to a TE-ITR.
5.4.1. A Stateless Solution to MTU Handling
An ITR stateless solution to handle MTU issues is described as
follows:
1. Define H to be the size, in octets, of the outer header an ITR
prepends to a packet. This includes the UDP and LISP header
lengths.
2. Define L to be the size, in octets, of the maximum-sized packet
an ITR can send to an ETR without the need for the ITR or any
intermediate routers to fragment the packet.
3. Define an architectural constant S for the maximum size of a
packet, in octets, an ITR must receive so the effective MTU can
be met. That is, S = L - H.
When an ITR receives a packet from a site-facing interface and adds H
octets worth of encapsulation to yield a packet size greater than L
octets, it resolves the MTU issue by first splitting the original
packet into 2 equal-sized fragments. A LISP header is then prepended
to each fragment. The size of the encapsulated fragments is then
(S/2 + H), which is less than the ITR's estimate of the path MTU
between the ITR and its correspondent ETR.
When an ETR receives encapsulated fragments, it treats them as two
individually encapsulated packets. It strips the LISP headers and
then forwards each fragment to the destination host of the
destination site. The two fragments are reassembled at the
Farinacci, et al. Experimental [Page 22]
RFC 6830 LISP January 2013
destination host into the single IP datagram that was originated by
the source host. Note that reassembly can happen at the ETR if the
encapsulated packet was fragmented at or after the ITR.
This behavior is performed by the ITR when the source host originates
a packet with the 'DF' field of the IP header set to 0. When the
'DF' field of the IP header is set to 1, or the packet is an IPv6
packet originated by the source host, the ITR will drop the packet
when the size is greater than L and send an ICMP Too Big message to
the source with a value of S, where S is (L - H).
When the outer-header encapsulation uses an IPv4 header, an
implementation SHOULD set the DF bit to 1 so ETR fragment reassembly
can be avoided. An implementation MAY set the DF bit in such headers
to 0 if it has good reason to believe there are unresolvable path MTU
issues between the sending ITR and the receiving ETR.
This specification RECOMMENDS that L be defined as 1500.
5.4.2. A Stateful Solution to MTU Handling
An ITR stateful solution to handle MTU issues is described as follows
and was first introduced in [OPENLISP]:
1. The ITR will keep state of the effective MTU for each Locator per
Map-Cache entry. The effective MTU is what the core network can
deliver along the path between the ITR and ETR.
2. When an IPv6-encapsulated packet, or an IPv4-encapsulated packet
with the DF bit set to 1, exceeds what the core network can
deliver, one of the intermediate routers on the path will send an
ICMP Too Big message to the ITR. The ITR will parse the ICMP
message to determine which Locator is affected by the effective
MTU change and then record the new effective MTU value in the
Map-Cache entry.
3. When a packet is received by the ITR from a source inside of the
site and the size of the packet is greater than the effective MTU
stored with the Map-Cache entry associated with the destination
EID the packet is for, the ITR will send an ICMP Too Big message
back to the source. The packet size advertised by the ITR in the
ICMP Too Big message is the effective MTU minus the LISP
encapsulation length.
Even though this mechanism is stateful, it has advantages over the
stateless IP fragmentation mechanism, by not involving the
destination host with reassembly of ITR fragmented packets.
Farinacci, et al. Experimental [Page 23]
RFC 6830 LISP January 2013
5.5. Using Virtualization and Segmentation with LISP
When multiple organizations inside of a LISP site are using private
addresses [RFC1918] as EID-Prefixes, their address spaces MUST remain
segregated due to possible address duplication. An Instance ID in
the address encoding can aid in making the entire AFI-based address
unique. See IANA Considerations (Section 14.2) for details on
possible address encodings.
An Instance ID can be carried in a LISP-encapsulated packet. An ITR
that prepends a LISP header will copy a 24-bit value used by the LISP
router to uniquely identify the address space. The value is copied
to the 'Instance ID' field of the LISP header, and the I-bit is set
to 1.
When an ETR decapsulates a packet, the Instance ID from the LISP
header is used as a table identifier to locate the forwarding table
to use for the inner destination EID lookup.
For example, an 802.1Q VLAN tag or VPN identifier could be used as a
24-bit Instance ID.
Farinacci, et al. Experimental [Page 24]
RFC 6830 LISP January 2013
6. EID-to-RLOC Mapping
6.1. LISP IPv4 and IPv6 Control-Plane Packet Formats
The following UDP packet formats are used by the LISP control plane.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Version| IHL |Type of Service| Total Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identification |Flags| Fragment Offset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Time to Live | Protocol = 17 | Header Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Routing Locator |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination Routing Locator |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ | Source Port | Dest Port |
UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ | UDP Length | UDP Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| LISP Message |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Farinacci, et al. Experimental [Page 25]
RFC 6830 LISP January 2013
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Version| Traffic Class | Flow Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Payload Length | Next Header=17| Hop Limit |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Source Routing Locator +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Destination Routing Locator +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ | Source Port | Dest Port |
UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ | UDP Length | UDP Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| LISP Message |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The LISP UDP-based messages are the Map-Request and Map-Reply
messages. When a UDP Map-Request is sent, the UDP source port is
chosen by the sender and the destination UDP port number is set to
4342. When a UDP Map-Reply is sent, the source UDP port number is
set to 4342 and the destination UDP port number is copied from the
source port of either the Map-Request or the invoking data packet.
Implementations MUST be prepared to accept packets when either the
source port or destination UDP port is set to 4342 due to NATs
changing port number values.
The 'UDP Length' field will reflect the length of the UDP header and
the LISP Message payload.
Farinacci, et al. Experimental [Page 26]
RFC 6830 LISP January 2013
The UDP checksum is computed and set to non-zero for Map-Request,
Map-Reply, Map-Register, and Encapsulated Control Message (ECM)
control messages. It MUST be checked on receipt, and if the checksum
fails, the packet MUST be dropped.
The format of control messages includes the UDP header so the
checksum and length fields can be used to protect and delimit message
boundaries.
6.1.1. LISP Packet Type Allocations
This section will be the authoritative source for allocating LISP
Type values and for defining LISP control message formats. Current
allocations are:
Reserved: 0 b'0000'
LISP Map-Request: 1 b'0001'
LISP Map-Reply: 2 b'0010'
LISP Map-Register: 3 b'0011'
LISP Map-Notify: 4 b'0100'
LISP Encapsulated Control Message: 8 b'1000'
6.1.2. Map-Request Message Format
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Type=1 |A|M|P|S|p|s| Reserved | IRC | Record Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Nonce . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| . . . Nonce |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source-EID-AFI | Source EID Address ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ITR-RLOC-AFI 1 | ITR-RLOC Address 1 ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ITR-RLOC-AFI n | ITR-RLOC Address n ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ | Reserved | EID mask-len | EID-Prefix-AFI |
Rec +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ | EID-Prefix ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Map-Reply Record ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Farinacci, et al. Experimental [Page 27]
RFC 6830 LISP January 2013
Packet field descriptions:
Type: 1 (Map-Request)
A: This is an authoritative bit, which is set to 0 for UDP-based
Map-Requests sent by an ITR. It is set to 1 when an ITR wants the
destination site to return the Map-Reply rather than the mapping
database system.
M: This is the map-data-present bit. When set, it indicates that a
Map-Reply Record segment is included in the Map-Request.
P: This is the probe-bit, which indicates that a Map-Request SHOULD
be treated as a Locator reachability probe. The receiver SHOULD
respond with a Map-Reply with the probe-bit set, indicating that
the Map-Reply is a Locator reachability probe reply, with the
nonce copied from the Map-Request. See Section 6.3.2 for more
details.
S: This is the Solicit-Map-Request (SMR) bit. See Section 6.6.2 for
details.
p: This is the PITR bit. This bit is set to 1 when a PITR sends a
Map-Request.
s: This is the SMR-invoked bit. This bit is set to 1 when an xTR is
sending a Map-Request in response to a received SMR-based
Map-Request.
Reserved: This field MUST be set to 0 on transmit and MUST be
ignored on receipt.
IRC: This 5-bit field is the ITR-RLOC Count, which encodes the
additional number of ('ITR-RLOC-AFI', 'ITR-RLOC Address') fields
present in this message. At least one (ITR-RLOC-AFI,
ITR-RLOC-Address) pair MUST be encoded. Multiple 'ITR-RLOC
Address' fields are used, so a Map-Replier can select which
destination address to use for a Map-Reply. The IRC value ranges
from 0 to 31. For a value of 0, there is 1 ITR-RLOC address
encoded; for a value of 1, there are 2 ITR-RLOC addresses encoded,
and so on up to 31, which encodes a total of 32 ITR-RLOC
addresses.
Record Count: This is the number of records in this Map-Request
message. A record is comprised of the portion of the packet that
is labeled 'Rec' above and occurs the number of times equal to
Record Count. For this version of the protocol, a receiver MUST
accept and process Map-Requests that contain one or more records,
Farinacci, et al. Experimental [Page 28]
RFC 6830 LISP January 2013
but a sender MUST only send Map-Requests containing one record.
Support for requesting multiple EIDs in a single Map-Request
message will be specified in a future version of the protocol.
Nonce: This is an 8-octet random value created by the sender of the
Map-Request. This nonce will be returned in the Map-Reply. The
security of the LISP mapping protocol critically depends on the
strength of the nonce in the Map-Request message. The nonce
SHOULD be generated by a properly seeded pseudo-random (or strong
random) source. See [RFC4086] for advice on generating security-
sensitive random data.
Source-EID-AFI: This is the address family of the 'Source EID
Address' field.
Source EID Address: This is the EID of the source host that
originated the packet that caused the Map-Request. When
Map-Requests are used for refreshing a Map-Cache entry or for
RLOC-Probing, an AFI value 0 is used and this field is of zero
length.
ITR-RLOC-AFI: This is the address family of the 'ITR-RLOC Address'
field that follows this field.
ITR-RLOC Address: This is used to give the ETR the option of
selecting the destination address from any address family for the
Map-Reply message. This address MUST be a routable RLOC address
of the sender of the Map-Request message.
EID mask-len: This is the mask length for the EID-Prefix.
EID-Prefix-AFI: This is the address family of the EID-Prefix
according to [AFI].
EID-Prefix: This prefix is 4 octets for an IPv4 address family and
16 octets for an IPv6 address family. When a Map-Request is sent
by an ITR because a data packet is received for a destination
where there is no mapping entry, the EID-Prefix is set to the
destination IP address of the data packet, and the 'EID mask-len'
is set to 32 or 128 for IPv4 or IPv6, respectively. When an xTR
wants to query a site about the status of a mapping it already has
cached, the EID-Prefix used in the Map-Request has the same mask
length as the EID-Prefix returned from the site when it sent a
Map-Reply message.
Farinacci, et al. Experimental [Page 29]
RFC 6830 LISP January 2013
Map-Reply Record: When the M-bit is set, this field is the size of a
single "Record" in the Map-Reply format. This Map-Reply record
contains the EID-to-RLOC mapping entry associated with the Source
EID. This allows the ETR that will receive this Map-Request to
cache the data if it chooses to do so.
6.1.3. EID-to-RLOC UDP Map-Request Message
A Map-Request is sent from an ITR when it needs a mapping for an EID,
wants to test an RLOC for reachability, or wants to refresh a mapping
before TTL expiration. For the initial case, the destination IP
address used for the Map-Request is the data packet's destination
address (i.e., the destination EID) that had a mapping cache lookup
failure. For the latter two cases, the destination IP address used
for the Map-Request is one of the RLOC addresses from the Locator-Set
of the Map-Cache entry. The source address is either an IPv4 or IPv6
RLOC address, depending on whether the Map-Request is using an IPv4
or IPv6 header, respectively. In all cases, the UDP source port
number for the Map-Request message is a 16-bit value selected by the
ITR/PITR, and the UDP destination port number is set to the well-
known destination port number 4342. A successful Map-Reply, which is
one that has a nonce that matches an outstanding Map-Request nonce,
will update the cached set of RLOCs associated with the EID-Prefix
range.
One or more Map-Request ('ITR-RLOC-AFI', 'ITR-RLOC-Address') fields
MUST be filled in by the ITR. The number of fields (minus 1) encoded
MUST be placed in the 'IRC' field. The ITR MAY include all locally
configured Locators in this list or just provide one locator address
from each address family it supports. If the ITR erroneously
provides no ITR-RLOC addresses, the Map-Replier MUST drop the
Map-Request.
Map-Requests can also be LISP encapsulated using UDP destination
port 4342 with a LISP Type value set to "Encapsulated Control
Message", when sent from an ITR to a Map-Resolver. Likewise,
Map-Requests are LISP encapsulated the same way from a Map-Server to
an ETR. Details on Encapsulated Map-Requests and Map-Resolvers can
be found in [RFC6833].
Map-Requests MUST be rate-limited. It is RECOMMENDED that a
Map-Request for the same EID-Prefix be sent no more than once per
second.
An ITR that is configured with mapping database information (i.e., it
is also an ETR) MAY optionally include those mappings in a
Map-Request. When an ETR configured to accept and verify such
"piggybacked" mapping data receives such a Map-Request and it does
Farinacci, et al. Experimental [Page 30]
RFC 6830 LISP January 2013
not have this mapping in the map-cache, it MAY originate a "verifying
Map-Request", addressed to the map-requesting ITR and the ETR MAY add
a Map-Cache entry. If the ETR has a Map-Cache entry that matches the
"piggybacked" EID and the RLOC is in the Locator-Set for the entry,
then it may send the "verifying Map-Request" directly to the
originating Map-Request source. If the RLOC is not in the
Locator-Set, then the ETR MUST send the "verifying Map-Request" to
the "piggybacked" EID. Doing this forces the "verifying Map-Request"
to go through the mapping database system to reach the authoritative
source of information about that EID, guarding against RLOC-spoofing
in the "piggybacked" mapping data.
6.1.4. Map-Reply Message Format
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Type=2 |P|E|S| Reserved | Record Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Nonce . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| . . . Nonce |
+-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Record TTL |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
R | Locator Count | EID mask-len | ACT |A| Reserved |
e +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
c | Rsvd | Map-Version Number | EID-Prefix-AFI |
o +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
r | EID-Prefix |
d +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| /| Priority | Weight | M Priority | M Weight |
| L +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| o | Unused Flags |L|p|R| Loc-AFI |
| c +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| \| Locator |
+-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Farinacci, et al. Experimental [Page 31]
RFC 6830 LISP January 2013
Packet field descriptions:
Type: 2 (Map-Reply)
P: This is the probe-bit, which indicates that the Map-Reply is in
response to a Locator reachability probe Map-Request. The 'Nonce'
field MUST contain a copy of the nonce value from the original
Map-Request. See Section 6.3.2 for more details.
E: This bit indicates that the ETR that sends this Map-Reply message
is advertising that the site is enabled for the Echo-Nonce Locator
reachability algorithm. See Section 6.3.1 for more details.
S: This is the Security bit. When set to 1, the following
authentication information will be appended to the end of the
Map-Reply. The detailed format of the Authentication Data Content
is for further study.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AD Type | Authentication Data Content . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Reserved: This field MUST be set to 0 on transmit and MUST be
ignored on receipt.
Record Count: This is the number of records in this reply message.
A record is comprised of that portion of the packet labeled
'Record' above and occurs the number of times equal to Record
Count.
Nonce: This is a 24-bit value set in a Data-Probe packet, or a
64-bit value from the Map-Request is echoed in this 'Nonce' field
of the Map-Reply. When a 24-bit value is supplied, it resides in
the low-order 64 bits of the 'Nonce' field.
Record TTL: This is the time in minutes the recipient of the
Map-Reply will store the mapping. If the TTL is 0, the entry
SHOULD be removed from the cache immediately. If the value is
0xffffffff, the recipient can decide locally how long to store the
mapping.
Locator Count: This is the number of Locator entries. A Locator
entry comprises what is labeled above as 'Loc'. The Locator count
can be 0, indicating that there are no Locators for the
EID-Prefix.
Farinacci, et al. Experimental [Page 32]
RFC 6830 LISP January 2013
EID mask-len: This is the mask length for the EID-Prefix.
ACT: This 3-bit field describes Negative Map-Reply actions. In any
other message type, these bits are set to 0 and ignored on
receipt. These bits are used only when the 'Locator Count' field
is set to 0. The action bits are encoded only in Map-Reply
messages. The actions defined are used by an ITR or PITR when a
destination EID matches a negative Map-Cache entry. Unassigned
values should cause a Map-Cache entry to be created, and when
packets match this negative cache entry, they will be dropped.
The current assigned values are:
(0) No-Action: The map-cache is kept alive, and no packet
encapsulation occurs.
(1) Natively-Forward: The packet is not encapsulated or dropped
but natively forwarded.
(2) Send-Map-Request: The packet invokes sending a Map-Request.
(3) Drop: A packet that matches this map-cache entry is dropped.
An ICMP Destination Unreachable message SHOULD be sent.
A: The Authoritative bit, when sent, is always set to 1 by an ETR.
When a Map-Server is proxy Map-Replying [RFC6833] for a LISP site,
the Authoritative bit is set to 0. This indicates to requesting
ITRs that the Map-Reply was not originated by a LISP node managed
at the site that owns the EID-Prefix.
Map-Version Number: When this 12-bit value is non-zero, the
Map-Reply sender is informing the ITR what the version number is
for the EID record contained in the Map-Reply. The ETR can
allocate this number internally but MUST coordinate this value
with other ETRs for the site. When this value is 0, there is no
versioning information conveyed. The Map-Version Number can be
included in Map-Request and Map-Register messages. See
Section 6.6.3 for more details.
EID-Prefix-AFI: Address family of the EID-Prefix according to [AFI].
EID-Prefix: This prefix is 4 octets for an IPv4 address family and
16 octets for an IPv6 address family.
Priority: Each RLOC is assigned a unicast Priority. Lower values
are more preferable. When multiple RLOCs have the same Priority,
they MAY be used in a load-split fashion. A value of 255 means
the RLOC MUST NOT be used for unicast forwarding.
Farinacci, et al. Experimental [Page 33]
RFC 6830 LISP January 2013
Weight: When priorities are the same for multiple RLOCs, the Weight
indicates how to balance unicast traffic between them. Weight is
encoded as a relative weight of total unicast packets that match
the mapping entry. For example, if there are 4 Locators in a
Locator-Set, where the Weights assigned are 30, 20, 20, and 10,
the first Locator will get 37.5% of the traffic, the 2nd and 3rd
Locators will get 25% of the traffic, and the 4th Locator will get
12.5% of the traffic. If all Weights for a Locator-Set are equal,
the receiver of the Map-Reply will decide how to load-split the
traffic. See Section 6.5 for a suggested hash algorithm to
distribute the load across Locators with the same Priority and
equal Weight values.
M Priority: Each RLOC is assigned a multicast Priority used by an
ETR in a receiver multicast site to select an ITR in a source
multicast site for building multicast distribution trees. A value
of 255 means the RLOC MUST NOT be used for joining a multicast
distribution tree. For more details, see [RFC6831].
M Weight: When priorities are the same for multiple RLOCs, the
Weight indicates how to balance building multicast distribution
trees across multiple ITRs. The Weight is encoded as a relative
weight (similar to the unicast Weights) of the total number of
trees built to the source site identified by the EID-Prefix. If
all Weights for a Locator-Set are equal, the receiver of the
Map-Reply will decide how to distribute multicast state across
ITRs. For more details, see [RFC6831].
Unused Flags: These are set to 0 when sending and ignored on
receipt.
L: When this bit is set, the Locator is flagged as a local Locator to
the ETR that is sending the Map-Reply. When a Map-Server is doing
proxy Map-Replying [RFC6833] for a LISP site, the L-bit is set to
0 for all Locators in this Locator-Set.
p: When this bit is set, an ETR informs the RLOC-Probing ITR that the
locator address for which this bit is set is the one being
RLOC-probed and MAY be different from the source address of the
Map-Reply. An ITR that RLOC-probes a particular Locator MUST use
this Locator for retrieving the data structure used to store the
fact that the Locator is reachable. The p-bit is set for a single
Locator in the same Locator-Set. If an implementation sets more
than one p-bit erroneously, the receiver of the Map-Reply MUST
select the first Locator. The p-bit MUST NOT be set for
Locator-Set records sent in Map-Request and Map-Register messages.
Farinacci, et al. Experimental [Page 34]
RFC 6830 LISP January 2013
R: This is set when the sender of a Map-Reply has a route to the
Locator in the Locator data record. This receiver may find this
useful to know if the Locator is up but not necessarily reachable
from the receiver's point of view. See also Section 6.4 for
another way the R-bit may be used.
Locator: This is an IPv4 or IPv6 address (as encoded by the
'Loc-AFI' field) assigned to an ETR. Note that the destination
RLOC address MAY be an anycast address. A source RLOC can be an
anycast address as well. The source or destination RLOC MUST NOT
be the broadcast address (255.255.255.255 or any subnet broadcast
address known to the router) and MUST NOT be a link-local
multicast address. The source RLOC MUST NOT be a multicast
address. The destination RLOC SHOULD be a multicast address if it
is being mapped from a multicast destination EID.
6.1.5. EID-to-RLOC UDP Map-Reply Message
A Map-Reply returns an EID-Prefix with a prefix length that is less
than or equal to the EID being requested. The EID being requested is
either from the destination field of an IP header of a Data-Probe or
the EID record of a Map-Request. The RLOCs in the Map-Reply are
globally routable IP addresses of all ETRs for the LISP site. Each
RLOC conveys status reachability but does not convey path
reachability from a requester's perspective. Separate testing of
path reachability is required. See Section 6.3 for details.
Note that a Map-Reply may contain different EID-Prefix granularity
(prefix + length) than the Map-Request that triggers it. This might
occur if a Map-Request were for a prefix that had been returned by an
earlier Map-Reply. In such a case, the requester updates its cache
with the new prefix information and granularity. For example, a
requester with two cached EID-Prefixes that are covered by a
Map-Reply containing one less-specific prefix replaces the entry with
the less-specific EID-Prefix. Note that the reverse, replacement of
one less-specific prefix with multiple more-specific prefixes, can
also occur, not by removing the less-specific prefix but rather by
adding the more-specific prefixes that, during a lookup, will
override the less-specific prefix.
Farinacci, et al. Experimental [Page 35]
RFC 6830 LISP January 2013
When an ETR is configured with overlapping EID-Prefixes, a
Map-Request with an EID that best matches any EID-Prefix MUST be
returned in a single Map-Reply message. For instance, if an ETR had
database mapping entries for EID-Prefixes:
10.0.0.0/8
10.1.0.0/16
10.1.1.0/24
10.1.2.0/24
A Map-Request for EID 10.1.1.1 would cause a Map-Reply with a record
count of 1 to be returned with a mapping record EID-Prefix of
10.1.1.0/24.
A Map-Request for EID 10.1.5.5 would cause a Map-Reply with a record
count of 3 to be returned with mapping records for EID-Prefixes
10.1.0.0/16, 10.1.1.0/24, and 10.1.2.0/24.
Note that not all overlapping EID-Prefixes need to be returned but
only the more-specific entries (note that in the second example above
10.0.0.0/8 was not returned for requesting EID 10.1.5.5) for the
matching EID-Prefix of the requesting EID. When more than one
EID-Prefix is returned, all SHOULD use the same Time to Live value so
they can all time out at the same time. When a more-specific
EID-Prefix is received later, its Time to Live value in the Map-Reply
record can be stored even when other less-specific entries exist.
When a less-specific EID-Prefix is received later, its map-cache
expiration time SHOULD be set to the minimum expiration time of any
more-specific EID-Prefix in the map-cache. This is done so the
integrity of the EID-Prefix set is wholly maintained and so no more-
specific entries are removed from the map-cache while keeping less-
specific entries.
Map-Replies SHOULD be sent for an EID-Prefix no more often than once
per second to the same requesting router. For scalability, it is
expected that aggregation of EID addresses into EID-Prefixes will
allow one Map-Reply to satisfy a mapping for the EID addresses in the
prefix range, thereby reducing the number of Map-Request messages.
Map-Reply records can have an empty Locator-Set. A Negative
Map-Reply is a Map-Reply with an empty Locator-Set. Negative
Map-Replies convey special actions by the sender to the ITR or PITR
that have solicited the Map-Reply. There are two primary
applications for Negative Map-Replies. The first is for a
Map-Resolver to instruct an ITR or PITR when a destination is for a
LISP site versus a non-LISP site, and the other is to source quench
Map-Requests that are sent for non-allocated EIDs.
Farinacci, et al. Experimental [Page 36]
RFC 6830 LISP January 2013
For each Map-Reply record, the list of Locators in a Locator-Set MUST
appear in the same order for each ETR that originates a Map-Reply
message. The Locator-Set MUST be sorted in order of ascending IP
address where an IPv4 locator address is considered numerically 'less
than' an IPv6 locator address.
When sending a Map-Reply message, the destination address is copied
from one of the 'ITR-RLOC' fields from the Map-Request. The ETR can
choose a locator address from one of the address families it
supports. For Data-Probes, the destination address of the Map-Reply
is copied from the source address of the Data-Probe message that is
invoking the reply. The source address of the Map-Reply is one of
the local IP addresses chosen to allow Unicast Reverse Path
Forwarding (uRPF) checks to succeed in the upstream service provider.
The destination port of a Map-Reply message is copied from the source
port of the Map-Request or Data-Probe, and the source port of the
Map-Reply message is set to the well-known UDP port 4342.
6.1.5.1. Traffic Redirection with Coarse EID-Prefixes
When an ETR is misconfigured or compromised, it could return coarse
EID-Prefixes in Map-Reply messages it sends. The EID-Prefix could
cover EID-Prefixes that are allocated to other sites, redirecting
their traffic to the Locators of the compromised site.
To solve this problem, there are two basic solutions that could be
used. The first is to have Map-Servers proxy Map-Reply on behalf of
ETRs so their registered EID-Prefixes are the ones returned in
Map-Replies. Since the interaction between an ETR and Map-Server is
secured with shared keys, it is easier for an ETR to detect
misbehavior. The second solution is to have ITRs and PITRs cache
EID-Prefixes with mask lengths that are greater than or equal to a
configured prefix length. This limits the damage to a specific width
of any EID-Prefix advertised but needs to be coordinated with the
allocation of site prefixes. These solutions can be used
independently or at the same time.
At the time of this writing, other approaches are being considered
and researched.
6.1.6. Map-Register Message Format
The usage details of the Map-Register message can be found in
specification [RFC6833]. This section solely defines the message
format.
The message is sent in UDP with a destination UDP port of 4342 and a
randomly selected UDP source port number.
Farinacci, et al. Experimental [Page 37]
RFC 6830 LISP January 2013
The Map-Register message format is:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Type=3 |P| Reserved |M| Record Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Nonce . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| . . . Nonce |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Key ID | Authentication Data Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Authentication Data ~
+-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Record TTL |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
R | Locator Count | EID mask-len | ACT |A| Reserved |
e +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
c | Rsvd | Map-Version Number | EID-Prefix-AFI |
o +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
r | EID-Prefix |
d +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| /| Priority | Weight | M Priority | M Weight |
| L +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| o | Unused Flags |L|p|R| Loc-AFI |
| c +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| \| Locator |
+-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Packet field descriptions:
Type: 3 (Map-Register)
P: This is the proxy Map-Reply bit. When set to 1, an ETR sends a
Map-Register message requesting the Map-Server to proxy a
Map-Reply. The Map-Server will send non-authoritative Map-Replies
on behalf of the ETR. Details on this usage can be found in
[RFC6833].
Reserved: This field MUST be set to 0 on transmit and MUST be
ignored on receipt.
M: This is the want-map-notify bit. When set to 1, an ETR is
requesting a Map-Notify message to be returned in response to
sending a Map-Register message. The Map-Notify message sent by a
Map-Server is used to acknowledge receipt of a Map-Register
message.
Farinacci, et al. Experimental [Page 38]
RFC 6830 LISP January 2013
Record Count: This is the number of records in this Map-Register
message. A record is comprised of that portion of the packet
labeled 'Record' above and occurs the number of times equal to
Record Count.
Nonce: This 8-octet 'Nonce' field is set to 0 in Map-Register
messages. Since the Map-Register message is authenticated, the
'Nonce' field is not currently used for any security function but
may be in the future as part of an anti-replay solution.
Key ID: This is a configured ID to find the configured Message
Authentication Code (MAC) algorithm and key value used for the
authentication function. See Section 14.4 for codepoint
assignments.
Authentication Data Length: This is the length in octets of the
'Authentication Data' field that follows this field. The length
of the 'Authentication Data' field is dependent on the MAC
algorithm used. The length field allows a device that doesn't
know the MAC algorithm to correctly parse the packet.
Authentication Data: This is the message digest used from the output
of the MAC algorithm. The entire Map-Register payload is
authenticated with this field preset to 0. After the MAC is
computed, it is placed in this field. Implementations of this
specification MUST include support for HMAC-SHA-1-96 [RFC2404],
and support for HMAC-SHA-256-128 [RFC4868] is RECOMMENDED.
The definition of the rest of the Map-Register can be found in
Section 6.1.4.
6.1.7. Map-Notify Message Format
The usage details of the Map-Notify message can be found in
specification [RFC6833]. This section solely defines the message
format.
The message is sent inside a UDP packet with source and destination
UDP ports equal to 4342.
Farinacci, et al. Experimental [Page 39]
RFC 6830 LISP January 2013
The Map-Notify message format is:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Type=4 | Reserved | Record Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Nonce . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| . . . Nonce |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Key ID | Authentication Data Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Authentication Data ~
+-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Record TTL |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
R | Locator Count | EID mask-len | ACT |A| Reserved |
e +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
c | Rsvd | Map-Version Number | EID-Prefix-AFI |
o +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
r | EID-Prefix |
d +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| /| Priority | Weight | M Priority | M Weight |
| L +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| o | Unused Flags |L|p|R| Loc-AFI |
| c +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| \| Locator |
+-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Packet field descriptions:
Type: 4 (Map-Notify)
The Map-Notify message has the same contents as a Map-Register
message. See the Map-Register section for field descriptions.
Farinacci, et al. Experimental [Page 40]
RFC 6830 LISP January 2013
6.1.8. Encapsulated Control Message Format
An Encapsulated Control Message (ECM) is used to encapsulate control
packets sent between xTRs and the mapping database system described
in [RFC6833].
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ | IPv4 or IPv6 Header |
OH | (uses RLOC addresses) |
\ | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ | Source Port = xxxx | Dest Port = 4342 |
UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ | UDP Length | UDP Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
LH |Type=8 |S| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ | IPv4 or IPv6 Header |
IH | (uses RLOC or EID addresses) |
\ | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ | Source Port = xxxx | Dest Port = yyyy |
UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ | UDP Length | UDP Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
LCM | LISP Control Message |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Packet header descriptions:
OH: The outer IPv4 or IPv6 header, which uses RLOC addresses in the
source and destination header address fields.
UDP: The outer UDP header with destination port 4342. The source
port is randomly allocated. The checksum field MUST be
non-zero.
LH: Type 8 is defined to be a "LISP Encapsulated Control Message",
and what follows is either an IPv4 or IPv6 header as encoded by
the first 4 bits after the 'Reserved' field.
S: This is the Security bit. When set to 1, the field following
the 'Reserved' field will have the following format. The
detailed format of the Authentication Data Content is for
further study.
Farinacci, et al. Experimental [Page 41]
RFC 6830 LISP January 2013
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AD Type | Authentication Data Content . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IH: The inner IPv4 or IPv6 header, which can use either RLOC or EID
addresses in the header address fields. When a Map-Request is
encapsulated in this packet format, the destination address in
this header is an EID.
UDP: The inner UDP header, where the port assignments depend on the
control packet being encapsulated. When the control packet is
a Map-Request or Map-Register, the source port is selected by
the ITR/PITR and the destination port is 4342. When the
control packet is a Map-Reply, the source port is 4342 and the
destination port is assigned from the source port of the
invoking Map-Request. Port number 4341 MUST NOT be assigned to
either port. The checksum field MUST be non-zero.
LCM: The format is one of the control message formats described in
this section. At this time, only Map-Request messages are
allowed to be encapsulated. In the future, PIM Join/Prune
messages [RFC6831] might be allowed. Encapsulating other types
of LISP control messages is for further study. When
Map-Requests are sent for RLOC-Probing purposes (i.e., the
probe-bit is set), they MUST NOT be sent inside Encapsulated
Control Messages.
6.2. Routing Locator Selection
Both the client-side and server-side may need control over the
selection of RLOCs for conversations between them. This control is
achieved by manipulating the 'Priority' and 'Weight' fields in
EID-to-RLOC Map-Reply messages. Alternatively, RLOC information MAY
be gleaned from received tunneled packets or EID-to-RLOC Map-Request
messages.
The following are different scenarios for choosing RLOCs and the
controls that are available:
o The server-side returns one RLOC. The client-side can only use
one RLOC. The server-side has complete control of the selection.
o The server-side returns a list of RLOCs where a subset of the list
has the same best Priority. The client can only use the subset
list according to the weighting assigned by the server-side. In
this case, the server-side controls both the subset list and
Farinacci, et al. Experimental [Page 42]
RFC 6830 LISP January 2013
load-splitting across its members. The client-side can use RLOCs
outside of the subset list if it determines that the subset list
is unreachable (unless RLOCs are set to a Priority of 255). Some
sharing of control exists: the server-side determines the
destination RLOC list and load distribution while the client-side
has the option of using alternatives to this list if RLOCs in the
list are unreachable.
o The server-side sets a Weight of 0 for the RLOC subset list. In
this case, the client-side can choose how the traffic load is
spread across the subset list. Control is shared by the server-
side determining the list and the client determining load
distribution. Again, the client can use alternative RLOCs if the
server-provided list of RLOCs is unreachable.
o Either side (more likely the server-side ETR) decides not to send
a Map-Request. For example, if the server-side ETR does not send
Map-Requests, it gleans RLOCs from the client-side ITR, giving the
client-side ITR responsibility for bidirectional RLOC reachability
and preferability. Server-side ETR gleaning of the client-side
ITR RLOC is done by caching the inner-header source EID and the
outer-header source RLOC of received packets. The client-side ITR
controls how traffic is returned and can alternate using an outer-
header source RLOC, which then can be added to the list the
server-side ETR uses to return traffic. Since no Priority or
Weights are provided using this method, the server-side ETR MUST
assume that each client-side ITR RLOC uses the same best Priority
with a Weight of zero. In addition, since EID-Prefix encoding
cannot be conveyed in data packets, the EID-to-RLOC Cache on
Tunnel Routers can grow to be very large.
o A "gleaned" Map-Cache entry, one learned from the source RLOC of a
received encapsulated packet, is only stored and used for a few
seconds, pending verification. Verification is performed by
sending a Map-Request to the source EID (the inner-header IP
source address) of the received encapsulated packet. A reply to
this "verifying Map-Request" is used to fully populate the
Map-Cache entry for the "gleaned" EID and is stored and used for
the time indicated from the 'TTL' field of a received Map-Reply.
When a verified Map-Cache entry is stored, data gleaning no longer
occurs for subsequent packets that have a source EID that matches
the EID-Prefix of the verified entry.
RLOCs that appear in EID-to-RLOC Map-Reply messages are assumed to be
reachable when the R-bit for the Locator record is set to 1. When
the R-bit is set to 0, an ITR or PITR MUST NOT encapsulate to the
RLOC. Neither the information contained in a Map-Reply nor that
stored in the mapping database system provides reachability
Farinacci, et al. Experimental [Page 43]
RFC 6830 LISP January 2013
information for RLOCs. Note that reachability is not part of the
mapping system and is determined using one or more of the Routing
Locator reachability algorithms described in the next section.
6.3. Routing Locator Reachability
Several mechanisms for determining RLOC reachability are currently
defined:
1. An ETR may examine the Locator-Status-Bits in the LISP header of
an encapsulated data packet received from an ITR. If the ETR is
also acting as an ITR and has traffic to return to the original
ITR site, it can use this status information to help select an
RLOC.
2. An ITR may receive an ICMP Network Unreachable or Host
Unreachable message for an RLOC it is using. This indicates that
the RLOC is likely down. Note that trusting ICMP messages may
not be desirable, but neither is ignoring them completely.
Implementations are encouraged to follow current best practices
in treating these conditions.
3. An ITR that participates in the global routing system can
determine that an RLOC is down if no BGP Routing Information Base
(RIB) route exists that matches the RLOC IP address.
4. An ITR may receive an ICMP Port Unreachable message from a
destination host. This occurs if an ITR attempts to use
interworking [RFC6832] and LISP-encapsulated data is sent to a
non-LISP-capable site.
5. An ITR may receive a Map-Reply from an ETR in response to a
previously sent Map-Request. The RLOC source of the Map-Reply is
likely up, since the ETR was able to send the Map-Reply to the
ITR.
6. When an ETR receives an encapsulated packet from an ITR, the
source RLOC from the outer header of the packet is likely up.
7. An ITR/ETR pair can use the Locator reachability algorithms
described in this section, namely Echo-Noncing or RLOC-Probing.
Farinacci, et al. Experimental [Page 44]
RFC 6830 LISP January 2013
When determining Locator up/down reachability by examining the
Locator-Status-Bits from the LISP-encapsulated data packet, an ETR
will receive up-to-date status from an encapsulating ITR about
reachability for all ETRs at the site. CE-based ITRs at the source
site can determine reachability relative to each other using the site
IGP as follows:
o Under normal circumstances, each ITR will advertise a default
route into the site IGP.
o If an ITR fails or if the upstream link to its PE fails, its
default route will either time out or be withdrawn.
Each ITR can thus observe the presence or lack of a default route
originated by the others to determine the Locator-Status-Bits it sets
for them.
RLOCs listed in a Map-Reply are numbered with ordinals 0 to n-1. The
Locator-Status-Bits in a LISP-encapsulated packet are numbered from 0
to n-1 starting with the least significant bit. For example, if an
RLOC listed in the 3rd position of the Map-Reply goes down (ordinal
value 2), then all ITRs at the site will clear the 3rd least
significant bit (xxxx x0xx) of the 'Locator-Status-Bits' field for
the packets they encapsulate.
When an ETR decapsulates a packet, it will check for any change in
the 'Locator-Status-Bits' field. When a bit goes from 1 to 0, the
ETR, if acting also as an ITR, will refrain from encapsulating
packets to an RLOC that is indicated as down. It will only resume
using that RLOC if the corresponding Locator-Status-Bit returns to a
value of 1. Locator-Status-Bits are associated with a Locator-Set
per EID-Prefix. Therefore, when a Locator becomes unreachable, the
Locator-Status-Bit that corresponds to that Locator's position in the
list returned by the last Map-Reply will be set to zero for that
particular EID-Prefix.
When ITRs at the site are not deployed in CE routers, the IGP can
still be used to determine the reachability of Locators, provided
they are injected into the IGP. This is typically done when a /32
address is configured on a loopback interface.
When ITRs receive ICMP Network Unreachable or Host Unreachable
messages as a method to determine unreachability, they will refrain
from using Locators that are described in Locator lists of
Map-Replies. However, using this approach is unreliable because many
network operators turn off generation of ICMP Destination Unreachable
messages.
Farinacci, et al. Experimental [Page 45]
RFC 6830 LISP January 2013
If an ITR does receive an ICMP Network Unreachable or Host
Unreachable message, it MAY originate its own ICMP Destination
Unreachable message destined for the host that originated the data
packet the ITR encapsulated.
Also, BGP-enabled ITRs can unilaterally examine the RIB to see if a
locator address from a Locator-Set in a mapping entry matches a
prefix. If it does not find one and BGP is running in the Default-
Free Zone (DFZ), it can decide to not use the Locator even though the
Locator-Status-Bits indicate that the Locator is up. In this case,
the path from the ITR to the ETR that is assigned the Locator is not
available. More details are in [LOC-ID-ARCH].
Optionally, an ITR can send a Map-Request to a Locator, and if a
Map-Reply is returned, reachability of the Locator has been
determined. Obviously, sending such probes increases the number of
control messages originated by Tunnel Routers for active flows, so
Locators are assumed to be reachable when they are advertised.
This assumption does create a dependency: Locator unreachability is
detected by the receipt of ICMP Host Unreachable messages. When a
Locator has been determined to be unreachable, it is not used for
active traffic; this is the same as if it were listed in a Map-Reply
with Priority 255.
The ITR can test the reachability of the unreachable Locator by
sending periodic Requests. Both Requests and Replies MUST be rate-
limited. Locator reachability testing is never done with data
packets, since that increases the risk of packet loss for end-to-end
sessions.
When an ETR decapsulates a packet, it knows that it is reachable from
the encapsulating ITR because that is how the packet arrived. In
most cases, the ETR can also reach the ITR but cannot assume this to
be true, due to the possibility of path asymmetry. In the presence
of unidirectional traffic flow from an ITR to an ETR, the ITR SHOULD
NOT use the lack of return traffic as an indication that the ETR is
unreachable. Instead, it MUST use an alternate mechanism to
determine reachability.
6.3.1. Echo Nonce Algorithm
When data flows bidirectionally between Locators from different
sites, a data-plane mechanism called "nonce echoing" can be used to
determine reachability between an ITR and ETR. When an ITR wants to
solicit a nonce echo, it sets the N- and E-bits and places a 24-bit
nonce [RFC4086] in the LISP header of the next encapsulated data
packet.
Farinacci, et al. Experimental [Page 46]
RFC 6830 LISP January 2013
When this packet is received by the ETR, the encapsulated packet is
forwarded as normal. When the ETR next sends a data packet to the
ITR, it includes the nonce received earlier with the N-bit set and
E-bit cleared. The ITR sees this "echoed nonce" and knows that the
path to and from the ETR is up.
The ITR will set the E-bit and N-bit for every packet it sends while
in the echo-nonce-request state. The time the ITR waits to process
the echoed nonce before it determines the path is unreachable is
variable and is a choice left for the implementation.
If the ITR is receiving packets from the ETR but does not see the
nonce echoed while being in the echo-nonce-request state, then the
path to the ETR is unreachable. This decision may be overridden by
other Locator reachability algorithms. Once the ITR determines that
the path to the ETR is down, it can switch to another Locator for
that EID-Prefix.
Note that "ITR" and "ETR" are relative terms here. Both devices MUST
be implementing both ITR and ETR functionality for the echo nonce
mechanism to operate.
The ITR and ETR may both go into the echo-nonce-request state at the
same time. The number of packets sent or the time during which echo
nonce requests are sent is an implementation-specific setting.
However, when an ITR is in the echo-nonce-request state, it can echo
the ETR's nonce in the next set of packets that it encapsulates and
subsequently continue sending echo-nonce-request packets.
This mechanism does not completely solve the forward path
reachability problem, as traffic may be unidirectional. That is, the
ETR receiving traffic at a site may not be the same device as an ITR
that transmits traffic from that site, or the site-to-site traffic is
unidirectional so there is no ITR returning traffic.
The echo-nonce algorithm is bilateral. That is, if one side sets the
E-bit and the other side is not enabled for echo-noncing, then the
echoing of the nonce does not occur and the requesting side may
erroneously consider the Locator unreachable. An ITR SHOULD only set
the E-bit in an encapsulated data packet when it knows the ETR is
enabled for echo-noncing. This is conveyed by the E-bit in the
Map-Reply message.
Note that other Locator reachability mechanisms are being researched
and can be used to compliment or even override the echo nonce
algorithm. See the next section for an example of control-plane
probing.
Farinacci, et al. Experimental [Page 47]
RFC 6830 LISP January 2013
6.3.2. RLOC-Probing Algorithm
RLOC-Probing is a method that an ITR or PITR can use to determine the
reachability status of one or more Locators that it has cached in a
Map-Cache entry. The probe-bit of the Map-Request and Map-Reply
messages is used for RLOC-Probing.
RLOC-Probing is done in the control plane on a timer basis, where an
ITR or PITR will originate a Map-Request destined to a locator
address from one of its own locator addresses. A Map-Request used as
an RLOC-probe is NOT encapsulated and NOT sent to a Map-Server or to
the mapping database system as one would when soliciting mapping
data. The EID record encoded in the Map-Request is the EID-Prefix of
the Map-Cache entry cached by the ITR or PITR. The ITR may include a
mapping data record for its own database mapping information that
contains the local EID-Prefixes and RLOCs for its site. RLOC-probes
are sent periodically using a jittered timer interval.
When an ETR receives a Map-Request message with the probe-bit set, it
returns a Map-Reply with the probe-bit set. The source address of
the Map-Reply is set according to the procedure described in
Section 6.1.5. The Map-Reply SHOULD contain mapping data for the
EID-Prefix contained in the Map-Request. This provides the
opportunity for the ITR or PITR that sent the RLOC-probe to get
mapping updates if there were changes to the ETR's database mapping
entries.
There are advantages and disadvantages of RLOC-Probing. The greatest
benefit of RLOC-Probing is that it can handle many failure scenarios
allowing the ITR to determine when the path to a specific Locator is
reachable or has become unreachable, thus providing a robust
mechanism for switching to using another Locator from the cached
Locator. RLOC-Probing can also provide rough Round-Trip Time (RTT)
estimates between a pair of Locators, which can be useful for network
management purposes as well as for selecting low delay paths. The
major disadvantage of RLOC-Probing is in the number of control
messages required and the amount of bandwidth used to obtain those
benefits, especially if the requirement for failure detection times
is very small.
Continued research and testing will attempt to characterize the
tradeoffs of failure detection times versus message overhead.
Farinacci, et al. Experimental [Page 48]
RFC 6830 LISP January 2013
6.4. EID Reachability within a LISP Site
A site may be multihomed using two or more ETRs. The hosts and
infrastructure within a site will be addressed using one or more
EID-Prefixes that are mapped to the RLOCs of the relevant ETRs in the
mapping system. One possible failure mode is for an ETR to lose
reachability to one or more of the EID-Prefixes within its own site.
When this occurs when the ETR sends Map-Replies, it can clear the
R-bit associated with its own Locator. And when the ETR is also an
ITR, it can clear its Locator-Status-Bit in the encapsulation data
header.
It is recognized that there are no simple solutions to the site
partitioning problem because it is hard to know which part of the
EID-Prefix range is partitioned and which Locators can reach any
sub-ranges of the EID-Prefixes. This problem is under investigation
with the expectation that experiments will tell us more. Note that
this is not a new problem introduced by the LISP architecture. The
problem exists today when a multihomed site uses BGP to advertise its
reachability upstream.
6.5. Routing Locator Hashing
When an ETR provides an EID-to-RLOC mapping in a Map-Reply message to
a requesting ITR, the Locator-Set for the EID-Prefix may contain
different Priority values for each locator address. When more than
one best Priority Locator exists, the ITR can decide how to load-
share traffic against the corresponding Locators.
The following hash algorithm may be used by an ITR to select a
Locator for a packet destined to an EID for the EID-to-RLOC mapping:
1. Either a source and destination address hash or the traditional
5-tuple hash can be used. The traditional 5-tuple hash includes
the source and destination addresses; source and destination TCP,
UDP, or Stream Control Transmission Protocol (SCTP) port numbers;
and the IP protocol number field or IPv6 next-protocol fields of
a packet that a host originates from within a LISP site. When a
packet is not a TCP, UDP, or SCTP packet, the source and
destination addresses only from the header are used to compute
the hash.
2. Take the hash value and divide it by the number of Locators
stored in the Locator-Set for the EID-to-RLOC mapping.
3. The remainder will yield a value of 0 to "number of Locators
minus 1". Use the remainder to select the Locator in the
Locator-Set.
Farinacci, et al. Experimental [Page 49]
RFC 6830 LISP January 2013
Note that when a packet is LISP encapsulated, the source port number
in the outer UDP header needs to be set. Selecting a hashed value
allows core routers that are attached to Link Aggregation Groups
(LAGs) to load-split the encapsulated packets across member links of
such LAGs. Otherwise, core routers would see a single flow, since
packets have a source address of the ITR, for packets that are
originated by different EIDs at the source site. A suggested setting
for the source port number computed by an ITR is a 5-tuple hash
function on the inner header, as described above.
Many core router implementations use a 5-tuple hash to decide how to
balance packet load across members of a LAG. The 5-tuple hash
includes the source and destination addresses of the packet and the
source and destination ports when the protocol number in the packet
is TCP or UDP. For this reason, UDP encoding is used for LISP
encapsulation.
6.6. Changing the Contents of EID-to-RLOC Mappings
Since the LISP architecture uses a caching scheme to retrieve and
store EID-to-RLOC mappings, the only way an ITR can get a more up-to-
date mapping is to re-request the mapping. However, the ITRs do not
know when the mappings change, and the ETRs do not keep track of
which ITRs requested its mappings. For scalability reasons, we want
to maintain this approach but need to provide a way for ETRs to
change their mappings and inform the sites that are currently
communicating with the ETR site using such mappings.
When adding a new Locator record in lexicographic order to the end of
a Locator-Set, it is easy to update mappings. We assume that new
mappings will maintain the same Locator ordering as the old mapping
but will just have new Locators appended to the end of the list. So,
some ITRs can have a new mapping while other ITRs have only an old
mapping that is used until they time out. When an ITR has only an
old mapping but detects bits set in the Locator-Status-Bits that
correspond to Locators beyond the list it has cached, it simply
ignores them. However, this can only happen for locator addresses
that are lexicographically greater than the locator addresses in the
existing Locator-Set.
When a Locator record is inserted in the middle of a Locator-Set, to
maintain lexicographic order, the SMR procedure in Section 6.6.2 is
used to inform ITRs and PITRs of the new Locator-Status-Bit mappings.
When a Locator record is removed from a Locator-Set, ITRs that have
the mapping cached will not use the removed Locator because the xTRs
will set the Locator-Status-Bit to 0. So, even if the Locator is in
the list, it will not be used. For new mapping requests, the xTRs
Farinacci, et al. Experimental [Page 50]
RFC 6830 LISP January 2013
can set the Locator AFI to 0 (indicating an unspecified address), as
well as setting the corresponding Locator-Status-Bit to 0. This
forces ITRs with old or new mappings to avoid using the removed
Locator.
If many changes occur to a mapping over a long period of time, one
will find empty record slots in the middle of the Locator-Set and new
records appended to the Locator-Set. At some point, it would be
useful to compact the Locator-Set so the Locator-Status-Bit settings
can be efficiently packed.
We propose here three approaches for Locator-Set compaction: one
operational mechanism and two protocol mechanisms. The operational
approach uses a clock sweep method. The protocol approaches use the
concept of Solicit-Map-Requests and Map-Versioning.
6.6.1. Clock Sweep
The clock sweep approach uses planning in advance and the use of
count-down TTLs to time out mappings that have already been cached.
The default setting for an EID-to-RLOC mapping TTL is 24 hours. So,
there is a 24-hour window to time out old mappings. The following
clock sweep procedure is used:
1. 24 hours before a mapping change is to take effect, a network
administrator configures the ETRs at a site to start the clock
sweep window.
2. During the clock sweep window, ETRs continue to send Map-Reply
messages with the current (unchanged) mapping records. The TTL
for these mappings is set to 1 hour.
3. 24 hours later, all previous cache entries will have timed out,
and any active cache entries will time out within 1 hour. During
this 1-hour window, the ETRs continue to send Map-Reply messages
with the current (unchanged) mapping records with the TTL set to
1 minute.
4. At the end of the 1-hour window, the ETRs will send Map-Reply
messages with the new (changed) mapping records. So, any active
caches can get the new mapping contents right away if not cached,
or in 1 minute if they had the mapping cached. The new mappings
are cached with a TTL equal to the TTL in the Map-Reply.
Farinacci, et al. Experimental [Page 51]
RFC 6830 LISP January 2013
6.6.2. Solicit-Map-Request (SMR)
Soliciting a Map-Request is a selective way for ETRs, at the site
where mappings change, to control the rate they receive requests for
Map-Reply messages. SMRs are also used to tell remote ITRs to update
the mappings they have cached.
Since the ETRs don't keep track of remote ITRs that have cached their
mappings, they do not know which ITRs need to have their mappings
updated. As a result, an ETR will solicit Map-Requests (called an
SMR message) from those sites to which it has been sending
encapsulated data for the last minute. In particular, an ETR will
send an SMR to an ITR to which it has recently sent encapsulated
data.
An SMR message is simply a bit set in a Map-Request message. An ITR
or PITR will send a Map-Request when they receive an SMR message.
Both the SMR sender and the Map-Request responder MUST rate-limit
these messages. Rate-limiting can be implemented as a global rate-
limiter or one rate-limiter per SMR destination.
The following procedure shows how an SMR exchange occurs when a site
is doing Locator-Set compaction for an EID-to-RLOC mapping:
1. When the database mappings in an ETR change, the ETRs at the site
begin to send Map-Requests with the SMR bit set for each Locator
in each Map-Cache entry the ETR caches.
2. A remote ITR that receives the SMR message will schedule sending
a Map-Request message to the source locator address of the SMR
message or to the mapping database system. A newly allocated
random nonce is selected, and the EID-Prefix used is the one
copied from the SMR message. If the source Locator is the only
Locator in the cached Locator-Set, the remote ITR SHOULD send a
Map-Request to the database mapping system just in case the
single Locator has changed and may no longer be reachable to
accept the Map-Request.
3. The remote ITR MUST rate-limit the Map-Request until it gets a
Map-Reply while continuing to use the cached mapping. When
Map-Versioning as described in Section 6.6.3 is used, an SMR
sender can detect if an ITR is using the most up-to-date database
mapping.
4. The ETRs at the site with the changed mapping will reply to the
Map-Request with a Map-Reply message that has a nonce from the
SMR-invoked Map-Request. The Map-Reply messages SHOULD be rate-
limited. This is important to avoid Map-Reply implosion.
Farinacci, et al. Experimental [Page 52]
RFC 6830 LISP January 2013
5. The ETRs at the site with the changed mapping record the fact
that the site that sent the Map-Request has received the new
mapping data in the Map-Cache entry for the remote site so the
Locator-Status-Bits are reflective of the new mapping for packets
going to the remote site. The ETR then stops sending SMR
messages.
Experimentation is in progress to determine the appropriate rate-
limit parameters.
For security reasons, an ITR MUST NOT process unsolicited
Map-Replies. To avoid Map-Cache entry corruption by a third party, a
sender of an SMR-based Map-Request MUST be verified. If an ITR
receives an SMR-based Map-Request and the source is not in the
Locator-Set for the stored Map-Cache entry, then the responding
Map-Request MUST be sent with an EID destination to the mapping
database system. Since the mapping database system is a more secure
way to reach an authoritative ETR, it will deliver the Map-Request to
the authoritative source of the mapping data.
When an ITR receives an SMR-based Map-Request for which it does not
have a cached mapping for the EID in the SMR message, it MAY not send
an SMR-invoked Map-Request. This scenario can occur when an ETR
sends SMR messages to all Locators in the Locator-Set it has stored
in its map-cache but the remote ITRs that receive the SMR may not be
sending packets to the site. There is no point in updating the ITRs
until they need to send, in which case they will send Map-Requests to
obtain a Map-Cache entry.
6.6.3. Database Map-Versioning
When there is unidirectional packet flow between an ITR and ETR, and
the EID-to-RLOC mappings change on the ETR, it needs to inform the
ITR so encapsulation to a removed Locator can stop and can instead be
started to a new Locator in the Locator-Set.
An ETR, when it sends Map-Reply messages, conveys its own Map-Version
Number. This is known as the Destination Map-Version Number. ITRs
include the Destination Map-Version Number in packets they
encapsulate to the site. When an ETR decapsulates a packet and
detects that the Destination Map-Version Number is less than the
current version for its mapping, the SMR procedure described in
Section 6.6.2 occurs.
Farinacci, et al. Experimental [Page 53]
RFC 6830 LISP January 2013
An ITR, when it encapsulates packets to ETRs, can convey its own
Map-Version Number. This is known as the Source Map-Version Number.
When an ETR decapsulates a packet and detects that the Source
Map-Version Number is greater than the last Map-Version Number sent
in a Map-Reply from the ITR's site, the ETR will send a Map-Request
to one of the ETRs for the source site.
A Map-Version Number is used as a sequence number per EID-Prefix, so
values that are greater are considered to be more recent. A value of
0 for the Source Map-Version Number or the Destination Map-Version
Number conveys no versioning information, and an ITR does no
comparison with previously received Map-Version Numbers.
A Map-Version Number can be included in Map-Register messages as
well. This is a good way for the Map-Server to assure that all ETRs
for a site registering to it will be synchronized according to
Map-Version Number.
See [RFC6834] for a more detailed analysis and description of
Database Map-Versioning.
7. Router Performance Considerations
LISP is designed to be very "hardware-based forwarding friendly". A
few implementation techniques can be used to incrementally implement
LISP:
o When a tunnel-encapsulated packet is received by an ETR, the outer
destination address may not be the address of the router. This
makes it challenging for the control plane to get packets from the
hardware. This may be mitigated by creating special Forwarding
Information Base (FIB) entries for the EID-Prefixes of EIDs served
by the ETR (those for which the router provides an RLOC
translation). These FIB entries are marked with a flag indicating
that control-plane processing should be performed. The forwarding
logic of testing for particular IP protocol number values is not
necessary. There are a few proven cases where no changes to
existing deployed hardware were needed to support the LISP data-
plane.
o On an ITR, prepending a new IP header consists of adding more
octets to a MAC rewrite string and prepending the string as part
of the outgoing encapsulation procedure. Routers that support
Generic Routing Encapsulation (GRE) tunneling [RFC2784] or 6to4
tunneling [RFC3056] may already support this action.
Farinacci, et al. Experimental [Page 54]
RFC 6830 LISP January 2013
o A packet's source address or interface the packet was received on
can be used to select VRF (Virtual Routing/Forwarding). The VRF's
routing table can be used to find EID-to-RLOC mappings.
For performance issues related to map-cache management, see
Section 12.
8. Deployment Scenarios
This section will explore how and where ITRs and ETRs can be deployed
and will discuss the pros and cons of each deployment scenario. For
a more detailed deployment recommendation, refer to [LISP-DEPLOY].
There are two basic deployment tradeoffs to consider: centralized
versus distributed caches; and flat, Recursive, or Re-encapsulating
Tunneling. When deciding on centralized versus distributed caching,
the following issues should be considered:
o Are the Tunnel Routers spread out so that the caches are spread
across all the memories of each router? A centralized cache is
when an ITR keeps a cache for all the EIDs it is encapsulating to.
The packet takes a direct path to the destination Locator. A
distributed cache is when an ITR needs help from other
re-encapsulating routers because it does not store all the cache
entries for the EIDs it is encapsulating to. So, the packet takes
a path through re-encapsulating routers that have a different set
of cache entries.
o Should management "touch points" be minimized by only choosing a
few Tunnel Routers, just enough for redundancy?
o In general, using more ITRs doesn't increase management load,
since caches are built and stored dynamically. On the other hand,
using more ETRs does require more management, since EID-Prefix-to-
RLOC mappings need to be explicitly configured.
When deciding on flat, Recursive, or Re-encapsulating Tunneling, the
following issues should be considered:
o Flat tunneling implements a single tunnel between the source site
and destination site. This generally offers better paths between
sources and destinations with a single tunnel path.
o Recursive Tunneling is when tunneled traffic is again further
encapsulated in another tunnel, either to implement VPNs or to
perform Traffic Engineering. When doing VPN-based tunneling, the
site has some control, since the site is prepending a new tunnel
header. In the case of TE-based tunneling, the site may have
Farinacci, et al. Experimental [Page 55]
RFC 6830 LISP January 2013
control if it is prepending a new tunnel header, but if the site's
ISP is doing the TE, then the site has no control. Recursive
Tunneling generally will result in suboptimal paths but with the
benefit of steering traffic to parts of the network that have more
resources available.
o The technique of re-encapsulation ensures that packets only
require one tunnel header. So, if a packet needs to be re-routed,
it is first decapsulated by the ETR and then re-encapsulated with
a new tunnel header using a new RLOC.
The next sub-sections will examine where Tunnel Routers can reside in
the network.
8.1. First-Hop/Last-Hop Tunnel Routers
By locating Tunnel Routers close to hosts, the EID-Prefix set is at
the granularity of an IP subnet. So, at the expense of more
EID-Prefix-to-RLOC sets for the site, the caches in each Tunnel
Router can remain relatively small. But caches always depend on the
number of non-aggregated EID destination flows active through these
Tunnel Routers.
With more Tunnel Routers doing encapsulation, the increase in control
traffic grows as well: since the EID granularity is greater, more
Map-Requests and Map-Replies are traveling between more routers.
The advantage of placing the caches and databases at these stub
routers is that the products deployed in this part of the network
have better price-memory ratios than their core router counterparts.
Memory is typically less expensive in these devices, and fewer routes
are stored (only IGP routes). These devices tend to have excess
capacity, both for forwarding and routing states.
LISP functionality can also be deployed in edge switches. These
devices generally have layer-2 ports facing hosts and layer-3 ports
facing the Internet. Spare capacity is also often available in these
devices.
8.2. Border/Edge Tunnel Routers
Using Customer Edge (CE) routers for tunnel endpoints allows the EID
space associated with a site to be reachable via a small set of RLOCs
assigned to the CE routers for that site. This is the default
behavior envisioned in the rest of this specification.
Farinacci, et al. Experimental [Page 56]
RFC 6830 LISP January 2013
This offers the opposite benefit of the first-hop/last-hop Tunnel
Router scenario: the number of mapping entries and network management
touch points is reduced, allowing better scaling.
One disadvantage is that fewer network resources are used to reach
host endpoints, thereby centralizing the point-of-failure domain and
creating network choke points at the CE router.
Note that more than one CE router at a site can be configured with
the same IP address. In this case, an RLOC is an anycast address.
This allows resilience between the CE routers. That is, if a CE
router fails, traffic is automatically routed to the other routers
using the same anycast address. However, this comes with the
disadvantage where the site cannot control the entrance point when
the anycast route is advertised out from all border routers. Another
disadvantage of using anycast Locators is the limited advertisement
scope of /32 (or /128 for IPv6) routes.
8.3. ISP Provider Edge (PE) Tunnel Routers
The use of ISP PE routers as tunnel endpoint routers is not the
typical deployment scenario envisioned in this specification. This
section attempts to capture some of the reasoning behind this
preference for implementing LISP on CE routers.
The use of ISP PE routers as tunnel endpoint routers gives an ISP,
rather than a site, control over the location of the egress tunnel
endpoints. That is, the ISP can decide whether the tunnel endpoints
are in the destination site (in either CE routers or last-hop routers
within a site) or at other PE edges. The advantage of this case is
that two tunnel headers can be avoided. By having the PE be the
first router on the path to encapsulate, it can choose a TE path
first, and the ETR can decapsulate and re-encapsulate for a tunnel to
the destination end site.
An obvious disadvantage is that the end site has no control over
where its packets flow or over the RLOCs used. Other disadvantages
include difficulty in synchronizing path liveness updates between CE
and PE routers.
As mentioned in earlier sections, a combination of these scenarios is
possible at the expense of extra packet header overhead; if both site
and provider want control, then Recursive or Re-encapsulating Tunnels
are used.
Farinacci, et al. Experimental [Page 57]
RFC 6830 LISP January 2013
8.4. LISP Functionality with Conventional NATs
LISP routers can be deployed behind Network Address Translator (NAT)
devices to provide the same set of packet services hosts have today
when they are addressed out of private address space.
It is important to note that a locator address in any LISP control
message MUST be a globally routable address and therefore SHOULD NOT
contain [RFC1918] addresses. If a LISP router is configured with
private addresses, they MUST be used only in the outer IP header so
the NAT device can translate properly. Otherwise, EID addresses MUST
be translated before encapsulation is performed. Both NAT
translation and LISP encapsulation functions could be co-located in
the same device.
More details on LISP address translation can be found in [RFC6832].
8.5. Packets Egressing a LISP Site
When a LISP site is using two ITRs for redundancy, the failure of one
ITR will likely shift outbound traffic to the second. This second
ITR's cache may not be populated with the same EID-to-RLOC mapping
entries as the first. If this second ITR does not have these
mappings, traffic will be dropped while the mappings are retrieved
from the mapping system. The retrieval of these messages may
increase the load of requests being sent into the mapping system.
Deployment and experimentation will determine whether this issue
requires more attention.
9. Traceroute Considerations
When a source host in a LISP site initiates a traceroute to a
destination host in another LISP site, it is highly desirable for it
to see the entire path. Since packets are encapsulated from the ITR
to the ETR, the hop across the tunnel could be viewed as a single
hop. However, LISP traceroute will provide the entire path so the
user can see 3 distinct segments of the path from a source LISP host
to a destination LISP host:
Farinacci, et al. Experimental [Page 58]
RFC 6830 LISP January 2013
Segment 1 (in source LISP site based on EIDs):
source host ---> first hop ... next hop ---> ITR
Segment 2 (in the core network based on RLOCs):
ITR ---> next hop ... next hop ---> ETR
Segment 3 (in the destination LISP site based on EIDs):
ETR ---> next hop ... last hop ---> destination host
For segment 1 of the path, ICMP Time Exceeded messages are returned
in the normal manner as they are today. The ITR performs a TTL
decrement and tests for 0 before encapsulating. Therefore, the ITR's
hop is seen by the traceroute source as having an EID address (the
address of the site-facing interface).
For segment 2 of the path, ICMP Time Exceeded messages are returned
to the ITR because the TTL decrement to 0 is done on the outer
header, so the destinations of the ICMP messages are the ITR RLOC
address and the source RLOC address of the encapsulated traceroute
packet. The ITR looks inside of the ICMP payload to inspect the
traceroute source so it can return the ICMP message to the address of
the traceroute client and also retain the core router IP address in
the ICMP message. This is so the traceroute client can display the
core router address (the RLOC address) in the traceroute output. The
ETR returns its RLOC address and responds to the TTL decrement to 0,
as the previous core routers did.
For segment 3, the next-hop router downstream from the ETR will be
decrementing the TTL for the packet that was encapsulated, sent into
the core, decapsulated by the ETR, and forwarded because it isn't the
final destination. If the TTL is decremented to 0, any router on the
path to the destination of the traceroute, including the next-hop
router or destination, will send an ICMP Time Exceeded message to the
source EID of the traceroute client. The ICMP message will be
encapsulated by the local ITR and sent back to the ETR in the
originated traceroute source site, where the packet will be delivered
to the host.
9.1. IPv6 Traceroute
IPv6 traceroute follows the procedure described above, since the
entire traceroute data packet is included in the ICMP Time Exceeded
message payload. Therefore, only the ITR needs to pay special
attention to forwarding ICMP messages back to the traceroute source.
Farinacci, et al. Experimental [Page 59]
RFC 6830 LISP January 2013
9.2. IPv4 Traceroute
For IPv4 traceroute, we cannot follow the above procedure, since IPv4
ICMP Time Exceeded messages only include the invoking IP header and
8 octets that follow the IP header. Therefore, when a core router
sends an IPv4 Time Exceeded message to an ITR, all the ITR has in the
ICMP payload is the encapsulated header it prepended, followed by a
UDP header. The original invoking IP header, and therefore the
identity of the traceroute source, is lost.
The solution we propose to solve this problem is to cache traceroute
IPv4 headers in the ITR and to match them up with corresponding IPv4
Time Exceeded messages received from core routers and the ETR. The
ITR will use a circular buffer for caching the IPv4 and UDP headers
of traceroute packets. It will select a 16-bit number as a key to
find them later when the IPv4 Time Exceeded messages are received.
When an ITR encapsulates an IPv4 traceroute packet, it will use the
16-bit number as the UDP source port in the encapsulating header.
When the ICMP Time Exceeded message is returned to the ITR, the UDP
header of the encapsulating header is present in the ICMP payload,
thereby allowing the ITR to find the cached headers for the
traceroute source. The ITR puts the cached headers in the payload
and sends the ICMP Time Exceeded message to the traceroute source
retaining the source address of the original ICMP Time Exceeded
message (a core router or the ETR of the site of the traceroute
destination).
The signature of a traceroute packet comes in two forms. The first
form is encoded as a UDP message where the destination port is
inspected for a range of values. The second form is encoded as an
ICMP message where the IP identification field is inspected for a
well-known value.
9.3. Traceroute Using Mixed Locators
When either an IPv4 traceroute or IPv6 traceroute is originated and
the ITR encapsulates it in the other address family header, one
cannot get all 3 segments of the traceroute. Segment 2 of the
traceroute cannot be conveyed to the traceroute source, since it is
expecting addresses from intermediate hops in the same address format
for the type of traceroute it originated. Therefore, in this case,
segment 2 will make the tunnel look like one hop. All the ITR has to
do to make this work is to not copy the inner TTL to the outer,
encapsulating header's TTL when a traceroute packet is encapsulated
using an RLOC from a different address family. This will cause no
TTL decrement to 0 to occur in core routers between the ITR and ETR.
Farinacci, et al. Experimental [Page 60]
RFC 6830 LISP January 2013
10. Mobility Considerations
There are several kinds of mobility, of which only some might be of
concern to LISP. Essentially, they are as follows.
10.1. Site Mobility
A site wishes to change its attachment points to the Internet, and
its LISP Tunnel Routers will have new RLOCs when it changes upstream
providers. Changes in EID-to-RLOC mappings for sites are expected to
be handled by configuration, outside of LISP.
10.2. Slow Endpoint Mobility
An individual endpoint wishes to move but is not concerned about
maintaining session continuity. Renumbering is involved. LISP can
help with the issues surrounding renumbering [RFC4192] [LISA96] by
decoupling the address space used by a site from the address spaces
used by its ISPs [RFC4984].
10.3. Fast Endpoint Mobility
Fast endpoint mobility occurs when an endpoint moves relatively
rapidly, changing its IP-layer network attachment point. Maintenance
of session continuity is a goal. This is where the Mobile IPv4
[RFC5944] and Mobile IPv6 [RFC6275] [RFC4866] mechanisms are used and
primarily where interactions with LISP need to be explored.
The problem is that as an endpoint moves, it may require changes to
the mapping between its EID and a set of RLOCs for its new network
location. When this is added to the overhead of Mobile IP binding
updates, some packets might be delayed or dropped.
In IPv4 mobility, when an endpoint is away from home, packets to it
are encapsulated and forwarded via a home agent that resides in the
home area the endpoint's address belongs to. The home agent will
encapsulate and forward packets either directly to the endpoint or to
a foreign agent that resides where the endpoint has moved to.
Packets from the endpoint may be sent directly to the correspondent
node, may be sent via the foreign agent, or may be reverse-tunneled
back to the home agent for delivery to the mobile node. As the
mobile node's EID or available RLOC changes, LISP EID-to-RLOC
Farinacci, et al. Experimental [Page 61]
RFC 6830 LISP January 2013
mappings are required for communication between the mobile node and
the home agent, whether via the foreign agent or not. As a mobile
endpoint changes networks, up to three LISP mapping changes may be
required:
o The mobile node moves from an old location to a new visited
network location and notifies its home agent that it has done so.
The Mobile IPv4 control packets the mobile node sends pass through
one of the new visited network's ITRs, which needs an EID-to-RLOC
mapping for the home agent.
o The home agent might not have the EID-to-RLOC mappings for the
mobile node's "care-of" address or its foreign agent in the new
visited network, in which case it will need to acquire them.
o When packets are sent directly to the correspondent node, it may
be that no traffic has been sent from the new visited network to
the correspondent node's network, and the new visited network's
ITR will need to obtain an EID-to-RLOC mapping for the
correspondent node's site.
In addition, if the IPv4 endpoint is sending packets from the new
visited network using its original EID, then LISP will need to
perform a route-returnability check on the new EID-to-RLOC mapping
for that EID.
In IPv6 mobility, packets can flow directly between the mobile node
and the correspondent node in either direction. The mobile node uses
its "care-of" address (EID). In this case, the route-returnability
check would not be needed but one more LISP mapping lookup may be
required instead:
o As above, three mapping changes may be needed for the mobile node
to communicate with its home agent and to send packets to the
correspondent node.
o In addition, another mapping will be needed in the correspondent
node's ITR, in order for the correspondent node to send packets to
the mobile node's "care-of" address (EID) at the new network
location.
When both endpoints are mobile, the number of potential mapping
lookups increases accordingly.
As a mobile node moves, there are not only mobility state changes in
the mobile node, correspondent node, and home agent, but also state
changes in the ITRs and ETRs for at least some EID-Prefixes.
Farinacci, et al. Experimental [Page 62]
RFC 6830 LISP January 2013
The goal is to support rapid adaptation, with little delay or packet
loss for the entire system. Also, IP mobility can be modified to
require fewer mapping changes. In order to increase overall system
performance, there may be a need to reduce the optimization of one
area in order to place fewer demands on another.
In LISP, one possibility is to "glean" information. When a packet
arrives, the ETR could examine the EID-to-RLOC mapping and use that
mapping for all outgoing traffic to that EID. It can do this after
performing a route-returnability check, to ensure that the new
network location does have an internal route to that endpoint.
However, this does not cover the case where an ITR (the node assigned
the RLOC) at the mobile-node location has been compromised.
Mobile IP packet exchange is designed for an environment in which all
routing information is disseminated before packets can be forwarded.
In order to allow the Internet to grow to support expected future
use, we are moving to an environment where some information may have
to be obtained after packets are in flight. Modifications to IP
mobility should be considered in order to optimize the behavior of
the overall system. Anything that decreases the number of new
EID-to-RLOC mappings needed when a node moves, or maintains the
validity of an EID-to-RLOC mapping for a longer time, is useful.
10.4. Fast Network Mobility
In addition to endpoints, a network can be mobile, possibly changing
xTRs. A "network" can be as small as a single router and as large as
a whole site. This is different from site mobility in that it is
fast and possibly short-lived, but different from endpoint mobility
in that a whole prefix is changing RLOCs. However, the mechanisms
are the same, and there is no new overhead in LISP. A map request
for any endpoint will return a binding for the entire mobile prefix.
If mobile networks become a more common occurrence, it may be useful
to revisit the design of the mapping service and allow for dynamic
updates of the database.
The issue of interactions between mobility and LISP needs to be
explored further. Specific improvements to the entire system will
depend on the details of mapping mechanisms. Mapping mechanisms
should be evaluated on how well they support session continuity for
mobile nodes.
Farinacci, et al. Experimental [Page 63]
RFC 6830 LISP January 2013
10.5. LISP Mobile Node Mobility
A mobile device can use the LISP infrastructure to achieve mobility
by implementing the LISP encapsulation and decapsulation functions
and acting as a simple ITR/ETR. By doing this, such a "LISP mobile
node" can use topologically independent EID IP addresses that are not
advertised into and do not impose a cost on the global routing
system. These EIDs are maintained at the edges of the mapping system
(in LISP Map-Servers and Map-Resolvers) and are provided on demand to
only the correspondents of the LISP mobile node.
Refer to [LISP-MN] for more details.
11. Multicast Considerations
A multicast group address, as defined in the original Internet
architecture, is an identifier of a grouping of topologically
independent receiver host locations. The address encoding itself
does not determine the location of the receiver(s). The multicast
routing protocol, and the network-based state the protocol creates,
determine where the receivers are located.
In the context of LISP, a multicast group address is both an EID and
a Routing Locator. Therefore, no specific semantic or action needs
to be taken for a destination address, as it would appear in an IP
header. Therefore, a group address that appears in an inner IP
header built by a source host will be used as the destination EID.
The outer IP header (the destination Routing Locator address),
prepended by a LISP router, will use the same group address as the
destination Routing Locator.
Having said that, only the source EID and source Routing Locator need
to be dealt with. Therefore, an ITR merely needs to put its own IP
address in the source 'Routing Locator' field when prepending the
outer IP header. This source Routing Locator address, like any other
Routing Locator address, MUST be globally routable.
Therefore, an EID-to-RLOC mapping does not need to be performed by an
ITR when a received data packet is a multicast data packet or when
processing a source-specific Join (either by IGMPv3 or PIM). But the
source Routing Locator is decided by the multicast routing protocol
in a receiver site. That is, an EID-to-RLOC translation is done at
control time.
Another approach is to have the ITR not encapsulate a multicast
packet and allow the packet built by the host to flow into the core
even if the source address is allocated out of the EID namespace. If
the RPF-Vector TLV [RFC5496] is used by PIM in the core, then core
Farinacci, et al. Experimental [Page 64]
RFC 6830 LISP January 2013
routers can RPF to the ITR (the locator address, which is injected
into core routing) rather than the host source address (the EID
address, which is not injected into core routing).
To avoid any EID-based multicast state in the network core, the first
approach is chosen for LISP-Multicast. Details for LISP-Multicast
and interworking with non-LISP sites are described in [RFC6831] and
[RFC6832].
12. Security Considerations
It is believed that most of the security mechanisms will be part of
the mapping database service when using control-plane procedures for
obtaining EID-to-RLOC mappings. For data-plane-triggered mappings,
as described in this specification, protection is provided against
ETR spoofing by using route-returnability (see Section 3) mechanisms
evidenced by the use of a 24-bit 'Nonce' field in the LISP
encapsulation header and a 64-bit 'Nonce' field in the LISP control
message.
The nonce, coupled with the ITR accepting only solicited Map-Replies,
provides a basic level of security, in many ways similar to the
security experienced in the current Internet routing system. It is
hard for off-path attackers to launch attacks against these LISP
mechanisms, as they do not have the nonce values. Sending a large
number of packets to accidentally find the right nonce value is
possible but would already by itself be a denial-of-service (DoS)
attack. On-path attackers can perform far more serious attacks, but
on-path attackers can launch serious attacks in the current Internet
as well, including eavesdropping, blocking, or redirecting traffic.
See more discussion on this topic in Section 6.1.5.1.
LISP does not rely on a PKI or a more heavyweight authentication
system. These systems challenge one of the primary design goals of
LISP -- scalability.
DoS attack prevention will depend on implementations rate-limiting
Map-Requests and Map-Replies to the control plane as well as
rate-limiting the number of data-triggered Map-Replies.
An incorrectly implemented or malicious ITR might choose to ignore
the Priority and Weights provided by the ETR in its Map-Reply. This
traffic-steering would be limited to the traffic that is sent by this
ITR's site and no more severe than if the site initiated a bandwidth
DoS attack on (one of) the ETR's ingress links. The ITR's site would
typically gain no benefit from not respecting the Weights and would
likely receive better service by abiding by them.
Farinacci, et al. Experimental [Page 65]
RFC 6830 LISP January 2013
To deal with map-cache exhaustion attempts in an ITR/PITR, the
implementation should consider putting a maximum cap on the number of
entries stored with a reserve list for special or frequently accessed
sites. This should be a configuration policy control set by the
network administrator who manages ITRs and PITRs. When overlapping
EID-Prefixes occur across multiple Map-Cache entries, the integrity
of the set must be wholly maintained. So, if a more-specific entry
cannot be added due to reaching the maximum cap, then none of the
less-specific entries should be stored in the map-cache.
Given that the ITR/PITR maintains a cache of EID-to-RLOC mappings,
cache sizing and maintenance are issues to be kept in mind during
implementation. It is a good idea to have instrumentation in place
to detect thrashing of the cache. Implementation experimentation
will be used to determine which cache management strategies work
best. In general, it is difficult to defend against cache-thrashing
attacks. It should be noted that an undersized cache in an ITR/PITR
not only causes adverse effects on the site or region it supports but
may also cause increased Map-Request loads on the mapping system.
"Piggybacked" mapping data as discussed in Section 6.1.3 specifies
how to handle such mappings and includes the possibility for an ETR
to temporarily accept such a mapping before verification when running
in "trusted" environments. In such cases, there is a potential
threat that a fake mapping could be inserted (even if only for a
short period) into a map-cache. As noted in Section 6.1.3, an ETR
MUST be specifically configured to run in such a mode and might
usefully only consider some specific ITRs as also running in that
same trusted environment.
There is a security risk implicit in the fact that ETRs generate the
EID-Prefix to which they are responding. An ETR can claim a shorter
prefix than it is actually responsible for. Various mechanisms to
ameliorate or resolve this issue will be examined in the future
[LISP-SEC].
Spoofing of inner-header addresses of LISP-encapsulated packets is
possible, as with any tunneling mechanism. ITRs MUST verify the
source address of a packet to be an EID that belongs to the site's
EID-Prefix range prior to encapsulation. An ETR must only
decapsulate and forward datagrams with an inner-header destination
that matches one of its EID-Prefix ranges. If, upon receipt and
decapsulation, the destination EID of a datagram does not match one
of the ETR's configured EID-Prefixes, the ETR MUST drop the datagram.
If a LISP-encapsulated packet arrives at an ETR, it SHOULD compare
the inner-header source EID address and the outer-header source RLOC
address with the mapping that exists in the mapping database. Then,
Farinacci, et al. Experimental [Page 66]
RFC 6830 LISP January 2013
when spoofing attacks occur, the outer-header source RLOC address can
be used to trace back the attack to the source site, using existing
operational tools.
This experimental specification does not address automated key
management (AKM). BCP 107 [RFC4107] provides guidance in this area.
In addition, at the time of this writing, substantial work is being
undertaken to improve security of the routing system [RFC6518]
[RFC6480] [BGP-SEC] [LISP-SEC]. Future work on LISP should address
the issues discussed in BCP 107 as well as other open security
considerations, which may require changes to this specification.
13. Network Management Considerations
Considerations for network management tools exist so the LISP
protocol suite can be operationally managed. These mechanisms can be
found in [LISP-MIB] and [RFC6835].
14. IANA Considerations
This section provides guidance to the Internet Assigned Numbers
Authority (IANA) regarding registration of values related to the LISP
specification, in accordance with BCP 26 [RFC5226].
There are four namespaces (listed in the sub-sections below) in LISP
that have been registered.
o LISP IANA registry allocations should not be made for purposes
unrelated to LISP routing or transport protocols.
o The following policies are used here with the meanings defined in
BCP 26: "Specification Required", "IETF Review", "Experimental
Use", and "First Come First Served".
14.1. LISP ACT and Flag Fields
New ACT values (Section 6.1.4) can be allocated through IETF review
or IESG approval. Four values have already been allocated by this
specification (Section 6.1.4).
In addition, LISP has a number of flag fields and reserved fields,
such as the LISP header flags field (Section 5.3). New bits for
flags in these fields can be implemented after IETF review or IESG
approval, but these need not be managed by IANA.
Farinacci, et al. Experimental [Page 67]
RFC 6830 LISP January 2013
14.2. LISP Address Type Codes
LISP Address [LCAF] type codes have a range from 0 to 255. New type
codes MUST be allocated consecutively, starting at 0. Type Codes
0-127 are to be assigned by IETF review or IESG approval.
Type Codes 128-255 are available according to the [RFC5226] First
Come First Served policy.
This registry, initially empty, is constructed for future use in
experimental work related to LISP Canonical Address Format (LCAF)
values. See [LCAF] for details of other possible unapproved address
encodings. The unapproved LCAF encodings are an area for further
study and experimentation.
14.3. LISP UDP Port Numbers
The IANA registry has allocated UDP port numbers 4341 and 4342 for
lisp-data and lisp-control operation, respectively. IANA has updated
the description for UDP ports 4341 and 4342 as follows:
lisp-data 4341 udp LISP Data Packets
lisp-control 4342 udp LISP Control Packets
14.4. LISP Key ID Numbers
The following Key ID values are defined by this specification as used
in any packet type that references a 'Key ID' field:
Name Number Defined in
-----------------------------------------------
None 0 n/a
HMAC-SHA-1-96 1 [RFC2404]
HMAC-SHA-256-128 2 [RFC4868]
Number values are in the range of 0 to 65535. The allocation of
values is on a first come first served basis.
15. Known Open Issues and Areas of Future Work
As an experimental specification, this work is, by definition,
incomplete. Specific areas where additional experience and work are
needed include the following:
o At present, only [RFC6836] is defined for implementing a database
of EID-to-RLOC mapping information. Additional research on other
mapping database systems is strongly encouraged.
Farinacci, et al. Experimental [Page 68]
RFC 6830 LISP January 2013
o Failure and recovery of LISP site partitioning (see Section 6.4)
in the presence of redundant configuration (see Section 8.5) needs
further research and experimentation.
o The characteristics of map-cache management under exceptional
conditions, such as denial-of-service attacks, are not fully
understood. Further experience is needed to determine whether
current caching methods are practical or in need of further
development. In particular, the performance, scaling, and
security characteristics of the map-cache will be discovered as
part of this experiment. Performance metrics to be observed are
packet reordering associated with the LISP Data-Probe and loss of
the first packet in a flow associated with map-caching. The
impact of these upon TCP will be observed. See Section 12 for
additional thoughts and considerations.
o Preliminary work has been done to ensure that sites employing LISP
can interconnect with the rest of the Internet. This work is
documented in [RFC6832], but further experimentation and
experience are needed.
o At present, no mechanism for automated key management for message
authentication is defined. Addressing automated key management is
necessary before this specification can be developed into a
Standards Track RFC. See Section 12 for further details regarding
security considerations.
o In order to maintain security and stability, Internet protocols
typically isolate the control and data planes. Therefore, user
activity cannot cause control-plane state to be created or
destroyed. LISP does not maintain this separation. The degree to
which the loss of separation impacts security and stability is a
topic for experimental observation.
o LISP allows for the use of different mapping database systems.
While only one [RFC6836] is currently well defined, each mapping
database will likely have some impact on the security of the
EID-to-RLOC mappings. How each mapping database system's security
properties impact LISP overall is for further study.
o An examination of the implications of LISP on Internet traffic,
applications, routers, and security is needed. This will help
implementors understand the consequences for network stability,
routing protocol function, routing scalability, migration and
backward compatibility, and implementation scalability (as
influenced by additional protocol components; additional state;
and additional processing for encapsulation, decapsulation, and
liveness).
Farinacci, et al. Experimental [Page 69]
RFC 6830 LISP January 2013
o Experiments need to verify that LISP produces no significant
change in the behavior of protocols run between end-systems over a
LISP infrastructure versus being run directly between those same
end-systems.
o Experiments need to verify that the issues raised in the Critique
section of [RFC6115] are either insignificant or have been
addressed by updates to LISP.
Other LISP documents may also include open issues and areas for
future work.
16. References
16.1. Normative References
[RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
August 1980.
[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791,
September 1981.
[RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and
E. Lear, "Address Allocation for Private Internets",
BCP 5, RFC 1918, February 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2404] Madson, C. and R. Glenn, "The Use of HMAC-SHA-1-96 within
ESP and AH", RFC 2404, November 1998.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, December 1998.
[RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition
of Explicit Congestion Notification (ECN) to IP",
RFC 3168, September 2001.
[RFC3232] Reynolds, J., "Assigned Numbers: RFC 1700 is Replaced by
an On-line Database", RFC 3232, January 2002.
[RFC4086] Eastlake, D., Schiller, J., and S. Crocker, "Randomness
Requirements for Security", BCP 106, RFC 4086, June 2005.
[RFC4632] Fuller, V. and T. Li, "Classless Inter-domain Routing
(CIDR): The Internet Address Assignment and Aggregation
Plan", BCP 122, RFC 4632, August 2006.
Farinacci, et al. Experimental [Page 70]
RFC 6830 LISP January 2013
[RFC4868] Kelly, S. and S. Frankel, "Using HMAC-SHA-256,
HMAC-SHA-384, and HMAC-SHA-512 with IPsec", RFC 4868,
May 2007.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
[RFC5496] Wijnands, IJ., Boers, A., and E. Rosen, "The Reverse Path
Forwarding (RPF) Vector TLV", RFC 5496, March 2009.
[RFC5944] Perkins, C., "IP Mobility Support for IPv4, Revised",
RFC 5944, November 2010.
[RFC6115] Li, T., "Recommendation for a Routing Architecture",
RFC 6115, February 2011.
[RFC6275] Perkins, C., Johnson, D., and J. Arkko, "Mobility Support
in IPv6", RFC 6275, July 2011.
[RFC6833] Farinacci, D. and V. Fuller, "Locator/ID Separation
Protocol (LISP) Map-Server Interface", RFC 6833,
January 2013.
[RFC6834] Iannone, L., Saucez, D., and O. Bonaventure, "Locator/ID
Separation Protocol (LISP) Map-Versioning", RFC 6834,
January 2013.
[RFC6836] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis,
"Locator/ID Separation Protocol Alternative Logical
Topology (LISP+ALT)", RFC 6836, January 2013.
16.2. Informative References
[AFI] IANA, "Address Family Numbers",
<http://www.iana.org/assignments/address-family-numbers>.
[BGP-SEC] Lepinski, M. and S. Turner, "An Overview of BGPSEC", Work
in Progress, May 2012.
[CHIAPPA] Chiappa, J., "Endpoints and Endpoint names: A Proposed
Enhancement to the Internet Architecture", 1999,
<http://mercury.lcs.mit.edu/~jnc/tech/endpoints.txt>.
[CONS] Brim, S., Chiappa, N., Farinacci, D., Fuller, V., Lewis,
D., and D. Meyer, "LISP-CONS: A Content distribution
Overlay Network Service for LISP", Work in Progress,
April 2008.
Farinacci, et al. Experimental [Page 71]
RFC 6830 LISP January 2013
[EMACS] Brim, S., Farinacci, D., Meyer, D., and J. Curran, "EID
Mappings Multicast Across Cooperating Systems for LISP",
Work in Progress, November 2007.
[LCAF] Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical
Address Format (LCAF)", Work in Progress, January 2013.
[LISA96] Lear, E., Tharp, D., Katinsky, J., and J. Coffin,
"Renumbering: Threat or Menace?", Usenix Tenth System
Administration Conference (LISA 96), October 1996.
[LISP-DEPLOY]
Jakab, L., Cabellos-Aparicio, A., Coras, F.,
Domingo-Pascual, J., and D. Lewis, "LISP Network Element
Deployment Considerations", Work in Progress,
October 2012.
[LISP-MIB] Schudel, G., Jain, A., and V. Moreno, "LISP MIB", Work
in Progress, January 2013.
[LISP-MN] Farinacci, D., Lewis, D., Meyer, D., and C. White, "LISP
Mobile Node", Work in Progress, October 2012.
[LISP-SEC] Maino, F., Ermagan, V., Cabellos, A., Saucez, D., and O.
Bonaventure, "LISP-Security (LISP-SEC)", Work in Progress,
October 2012.
[LOC-ID-ARCH]
Meyer, D. and D. Lewis, "Architectural Implications of
Locator/ID Separation", Work in Progress, January 2009.
[OPENLISP] Iannone, L., Saucez, D., and O. Bonaventure, "OpenLISP
Implementation Report", Work in Progress, July 2008.
[RADIR] Narten, T., "On the Scalability of Internet Routing", Work
in Progress, February 2010.
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, November 1987.
[RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P.
Traina, "Generic Routing Encapsulation (GRE)", RFC 2784,
March 2000.
[RFC3056] Carpenter, B. and K. Moore, "Connection of IPv6 Domains
via IPv4 Clouds", RFC 3056, February 2001.
Farinacci, et al. Experimental [Page 72]
RFC 6830 LISP January 2013
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261,
June 2002.
[RFC4107] Bellovin, S. and R. Housley, "Guidelines for Cryptographic
Key Management", BCP 107, RFC 4107, June 2005.
[RFC4192] Baker, F., Lear, E., and R. Droms, "Procedures for
Renumbering an IPv6 Network without a Flag Day", RFC 4192,
September 2005.
[RFC4866] Arkko, J., Vogt, C., and W. Haddad, "Enhanced Route
Optimization for Mobile IPv6", RFC 4866, May 2007.
[RFC4984] Meyer, D., Zhang, L., and K. Fall, "Report from the IAB
Workshop on Routing and Addressing", RFC 4984,
September 2007.
[RFC6480] Lepinski, M. and S. Kent, "An Infrastructure to Support
Secure Internet Routing", RFC 6480, February 2012.
[RFC6518] Lebovitz, G. and M. Bhatia, "Keying and Authentication for
Routing Protocols (KARP) Design Guidelines", RFC 6518,
February 2012.
[RFC6831] Farinacci, D., Meyer, D., Zwiebel, J., and S. Venaas, "The
Locator/ID Separation Protocol (LISP) for Multicast
Environments", RFC 6831, January 2013.
[RFC6832] Lewis, D., Meyer, D., Farinacci, D., and V. Fuller,
"Interworking between Locator/ID Separation Protocol
(LISP) and Non-LISP Sites", RFC 6832, January 2013.
[RFC6835] Farinacci, D. and D. Meyer, "The Locator/ID Separation
Protocol Internet Groper (LIG)", RFC 6835, January 2013.
[RFC6837] Lear, E., "NERD: A Not-so-novel Endpoint ID (EID) to
Routing Locator (RLOC) Database", RFC 6837, January 2013.
[UDP-TUNNELS]
Eubanks, M., Chimento, P., and M. Westerlund, "IPv6 and
UDP Checksums for Tunneled Packets", Work in Progress,
January 2013.
[UDP-ZERO] Fairhurst, G. and M. Westerlund, "Applicability Statement
for the use of IPv6 UDP Datagrams with Zero Checksums",
Work in Progress, December 2012.
Farinacci, et al. Experimental [Page 73]
RFC 6830 LISP January 2013
Appendix A. Acknowledgments
An initial thank you goes to Dave Oran for planting the seeds for the
initial ideas for LISP. His consultation continues to provide value
to the LISP authors.
A special and appreciative thank you goes to Noel Chiappa for
providing architectural impetus over the past decades on separation
of location and identity, as well as detailed reviews of the LISP
architecture and documents, coupled with enthusiasm for making LISP a
practical and incremental transition for the Internet.
The authors would like to gratefully acknowledge many people who have
contributed discussions and ideas to the making of this proposal.
They include Scott Brim, Andrew Partan, John Zwiebel, Jason Schiller,
Lixia Zhang, Dorian Kim, Peter Schoenmaker, Vijay Gill, Geoff Huston,
David Conrad, Mark Handley, Ron Bonica, Ted Seely, Mark Townsley,
Chris Morrow, Brian Weis, Dave McGrew, Peter Lothberg, Dave Thaler,
Eliot Lear, Shane Amante, Ved Kafle, Olivier Bonaventure, Luigi
Iannone, Robin Whittle, Brian Carpenter, Joel Halpern, Terry
Manderson, Roger Jorgensen, Ran Atkinson, Stig Venaas, Iljitsch van
Beijnum, Roland Bless, Dana Blair, Bill Lynch, Marc Woolward, Damien
Saucez, Damian Lezama, Attilla De Groot, Parantap Lahiri, David
Black, Roque Gagliano, Isidor Kouvelas, Jesper Skriver, Fred Templin,
Margaret Wasserman, Sam Hartman, Michael Hofling, Pedro Marques, Jari
Arkko, Gregg Schudel, Srinivas Subramanian, Amit Jain, Xu Xiaohu,
Dhirendra Trivedi, Yakov Rekhter, John Scudder, John Drake, Dimitri
Papadimitriou, Ross Callon, Selina Heimlich, Job Snijders, Vina
Ermagan, Albert Cabellos, Fabio Maino, Victor Moreno, Chris White,
Clarence Filsfils, and Alia Atlas.
This work originated in the Routing Research Group (RRG) of the IRTF.
An individual submission was converted into the IETF LISP working
group document that became this RFC.
The LISP working group would like to give a special thanks to Jari
Arkko, the Internet Area AD at the time that the set of LISP
documents were being prepared for IESG last call, and for his
meticulous reviews and detailed commentaries on the 7 working group
last call documents progressing toward experimental RFCs.
Farinacci, et al. Experimental [Page 74]
RFC 6830 LISP January 2013
Authors' Addresses
Dino Farinacci
Cisco Systems
Tasman Drive
San Jose, CA 95134
USA
EMail: farinacci@gmail.com
Vince Fuller
EMail: vaf@vaf.net
Dave Meyer
Cisco Systems
170 Tasman Drive
San Jose, CA
USA
EMail: dmm@1-4-5.net
Darrel Lewis
Cisco Systems
170 Tasman Drive
San Jose, CA
USA
EMail: darlewis@cisco.com
Farinacci, et al. Experimental [Page 75]
ERRATA
