Internet DRAFT - draft-nitinb-i2rs-rib-info-model
draft-nitinb-i2rs-rib-info-model
Network Working Group N. Bahadur, Ed.
Internet-Draft R. Folkes, Ed.
Intended status: Informational Juniper Networks, Inc.
Expires: February 22, 2014 S. Kini
Ericsson
J. Medved
Cisco
August 21, 2013
Routing Information Base Info Model
draft-nitinb-i2rs-rib-info-model-02
Abstract
Routing and routing functions in enterprise and carrier networks are
typically performed by network devices (routers and switches) using a
routing information base (RIB). Protocols and configuration push
data into the RIB and the RIB manager install state into the
hardware; for packet forwarding. This draft specifies an information
model for the RIB to enable defining a standardized data model. Such
a data model can be used to define an interface to the RIB from an
entity that may even be external to the network device. This
interface can be used to support new use-cases being defined by the
IETF I2RS WG.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on February 22, 2014.
Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved.
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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
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Conventions used in this document . . . . . . . . . . . . 6
2. RIB data . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1. RIB definition . . . . . . . . . . . . . . . . . . . . . . 6
2.2. Routing instance . . . . . . . . . . . . . . . . . . . . . 7
2.3. Route . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.4. Nexthop . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.4.1. Nexthop types . . . . . . . . . . . . . . . . . . . . 12
2.4.2. Nexthop list attributes . . . . . . . . . . . . . . . 13
2.4.3. Nexthop content . . . . . . . . . . . . . . . . . . . 14
2.4.4. Nexthop attributes . . . . . . . . . . . . . . . . . . 14
2.4.5. Nexthop vendor attributes . . . . . . . . . . . . . . 15
2.4.6. Special nexthops . . . . . . . . . . . . . . . . . . . 15
3. Reading from the RIB . . . . . . . . . . . . . . . . . . . . . 16
4. Writing to the RIB . . . . . . . . . . . . . . . . . . . . . . 16
5. Events and Notifications . . . . . . . . . . . . . . . . . . . 16
6. RIB grammar . . . . . . . . . . . . . . . . . . . . . . . . . 17
7. Using the RIB grammar . . . . . . . . . . . . . . . . . . . . 19
7.1. Using route preference and metric . . . . . . . . . . . . 20
7.2. Using different nexthops types . . . . . . . . . . . . . . 20
7.2.1. Tunnel nexthops . . . . . . . . . . . . . . . . . . . 20
7.2.2. Replication lists . . . . . . . . . . . . . . . . . . 20
7.2.3. Weighted lists . . . . . . . . . . . . . . . . . . . . 21
7.2.4. Protection lists . . . . . . . . . . . . . . . . . . . 21
7.2.5. Nexthop chains . . . . . . . . . . . . . . . . . . . . 22
7.2.6. Lists of lists . . . . . . . . . . . . . . . . . . . . 22
7.3. Performing multicast . . . . . . . . . . . . . . . . . . . 22
7.4. Solving optimized exit control . . . . . . . . . . . . . . 23
8. RIB operations at scale . . . . . . . . . . . . . . . . . . . 23
8.1. RIB reads . . . . . . . . . . . . . . . . . . . . . . . . 24
8.2. RIB writes . . . . . . . . . . . . . . . . . . . . . . . . 24
8.3. RIB events and notifications . . . . . . . . . . . . . . . 24
9. Security Considerations . . . . . . . . . . . . . . . . . . . 24
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 24
12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 25
12.1. Normative References . . . . . . . . . . . . . . . . . . . 25
12.2. Informative References . . . . . . . . . . . . . . . . . . 25
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 26
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1. Introduction
Routing and routing functions in enterprise and carrier networks are
traditionally performed in network devices. Traditionally routers
run routing protocols and the routing protocols (along with static
config) populates the Routing information base (RIB) of the router.
The RIB is managed by the RIB manager and it provides a north-bound
interface to its clients i.e. the routing protocols to insert routes
into the RIB. The RIB manager consults the RIB and decides how to
program the forwarding information base (FIB) of the hardware by
interfacing with the FIB-manager. The relationship between these
entities is shown in Figure 1.
+-------------+ +-------------+
|RIB-Client 1 | ...... |RIB-Client N |
+-------------+ +-------------+
^ ^
| |
+----------------------+
|
V
+---------------------+
|RIB-Manager |
| |
| +-----+ |
| | RIB | |
| +-----+ |
+---------------------+
^
|
+---------------------------------+
| |
V V
+-------------+ +-------------+
|FIB-Manager 1| |FIB-Manager M|
| +-----+ | .......... | +-----+ |
| | FIB | | | | FIB | |
| +-----+ | | +-----+ |
+-------------+ +-------------+
Figure 1: RIB-Manager, RIB-Clients and FIB-Managers
Routing protocols are inherently distributed in nature and each
router makes an independent decision based on the routing data
received from its peers. With the advent of newer deployment
paradigms and the need for specialized applications, there is an
emerging need to guide the router's routing function
[I-D.atlas-i2rs-problem-statement]. Traditional network-device
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protocol-based RIB population suffices for most use cases where
distributed network control works. However there are use cases in
which the network admins today configure static routes, policies and
RIB import/export rules on the routers. There is also a growing list
of use cases [I-D.white-i2rs-use-case],
[I-D.hares-i2rs-use-case-vn-vc] in which a network admin might want
to program the RIB based on data unrelated to just routing (within
that network's domain). It could be based on routing data in
adjacent domain or it could be based on load on storage and compute
in the given domain. Or it could simply be a programmatic way of
creating on-demand dynamic overlays between compute hosts (without
requiring the hosts to run traditional routing protocols). If there
was a standardized programmatic interface to a RIB, it would fuel
further networking applications targeted towards specific niches.
A programmatic interface to the RIB involves 2 types of operations -
reading what's in the RIB and adding/modifying/deleting contents of
the RIB. [I-D.white-i2rs-use-case] lists various use-cases which
require read and/or write manipulation of the RIB.
In order to understand what is in a router's RIB, methods like per-
protocol SNMP MIBs and show output screen scraping are being used.
These methods are not scalable, since they are client pull mechanisms
and not proactive push (from the router) mechanisms. Screen scraping
is error prone (since the output format can change) and vendor
dependent. Building a RIB from per-protocol MIBs is error prone
since the MIB data represents protocol data and not the exact
information that went into the RIB. Thus, just getting read-only RIB
information from a router is a hard task.
Adding content to the RIB from an external entity can be done today
using static configuration support provided by router vendors.
However the mix of what can be modified in the RIB varies from vendor
to vendor and the way of configuring it is also vendor dependent.
This makes it hard for an external entity to program a multi-vendor
network in a consistent and vendor independent way.
The purpose of this draft is to specify an information model for the
RIB. Using the information model, one can build a detailed data
model for the RIB. And that data model could then be used by an
external entity to program a network device.
The rest of this document is organized as follows. Section 2 goes
into the details of what constitutes and can be programmed in a RIB.
Guidelines for reading and writing the RIB are provided in Section 3
and Section 4 respectively. Section 5 provides a high-level view of
the events and notifications going from a network device to an
external entity, to update the external entity on asynchronous
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events. The RIB grammar is specified in Section 6. Examples of
using the RIB grammar are shown in Section 7. Section 8 covers
considerations for performing RIB operations at scale.
1.1. Conventions used in this document
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].
2. RIB data
This section describes the details of a RIB. It makes forward
references to objects in the RIB grammar (Section 6). A high-level
description of the RIB contents is as shown below.
routing-instance
| |
| |
0..N | | 1..N
| |
interface(s) RIB(s)
|
|
| 0..N
route(s)
2.1. RIB definition
A RIB is an entity that contains routes. A RIB is identified by its
name and a RIB is contained within a routing instance (Section 2.2).
The name MUST be unique within a routing instance. All routes in a
given RIB MUST be of the same type (e.g. IPv4). Each RIB MUST
belong to some routing instance.
A RIB can be tagged with a MULTI_TOPOLOGY_ID. If a routing instance
is divided into multiple logical topologies, then the multi-topology
field is used to distinguish one topology from the other, so as to
keep routes from one topology independent of routes from another
topology.
If a routing instance contains multiple RIBs of the same type (e.g.
IPv4), then a MULTI_TOPOLOGY_ID MUST be associated with each such
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RIB. Multiple RIBs are useful when describing multiple topology IGP
(Interior Gateway Protocol) networks (see [RFC4915] and [RFC5120] ).
In a given routing instance, MULTI_TOPOLOGY_ID MUST be unique across
RIBs of the same type.
Each RIB can be optionally associated with a ENABLE_IP_RPF_CHECK
attribute that enables Reverse path forwarding (RPF) checks on all IP
routes in that RIB. Reverse path forwarding (RPF) check is used to
prevent spoofing and limit malicious traffic. For IP packets, the IP
source address is looked up and the rpf interface(s) associated with
the route for that IP source address is found. If the incoming IP
packet's interface matches one of the rpf interface(s), then the IP
packet is forwarded based on its IP destination address; otherwise,
the IP packet is discarded.
2.2. Routing instance
A routing instance, in the context of the RIB information model, is a
collection of RIBs, interfaces, and routing parameters. A routing
instance creates a logical slice of the router and allows different
logical slices; across a set of routers; to communicate with other
each. Layer 3 Virtual Private Networks (VPN), Layer 2 VPNs (L2VPN)
and Virtual Private Lan Service (VPLS) can be modeled as routing
instances. Note that modeling a Layer 2 VPN using a routing instance
only models the Layer-3 (RIB) aspect and does not model any layer-2
information (like ARP) that might be associated with the L2VPN.
The set of interfaces indicates which interfaces are associated with
this routing instance. The RIBs specify how incoming traffic is to
be forwarded. And the routing parameters control the information in
the RIBs. The intersection set of interfaces of 2 routing instances
SHOULD be the null set. In other words, an interface MUST NOT be
present in 2 routing instances. Thus a routing instance describes
the routing information and parameters across a set of interfaces.
A routing instance MUST contain the following mandatory fields.
o INSTANCE_NAME: A routing instance is identified by its name,
INSTANCE_NAME. This SHOULD be unique across all routing instances
in a given network device.
o INSTANCE_DISTINGUISHER: Each routing instance MUST have a
distinguisher associated with it. It enables one to distinguish
routes across routing instances. The route distinguisher MUST be
unique across all routing instances in a given network device.
How the INSTANCE_DISTINGUISHER is allocated and kept unique is
outside the scope of this document. The instance distinguisher
maps well to BGP route-distinguisher for virtual private networks
(VPNs). However, the same concept can be used for other use-cases
as well.
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o rib-list: This is the list of RIBs associated with this routing
instance. Each routing instance can have multiple RIBs to
represent routes of different types. For example, one would put
IPv4 routes in one RIB and MPLS routes in another RIB.
A routing instance MAY contain the following optional fields.
o interface-list: This represents the list of interfaces associated
with this routing instance. The interface list helps constrain
the boundaries of packet forwarding. Packets coming on these
interfaces are directly associated with the given routing
instance. The interface list contains a list of identifiers, with
each identifier uniquely identifying an interface.
o ROUTER_ID: The router-id field identifies the network device in
control plane interactions with other network devices. This field
is to be used if one wants to virtualize a physical router into
multiple virtual routers. Each virtual router MUST have a unique
router-id. ROUTER_ID MUST be unique across all network devices in
a given domain.
o as-data: This is an identifier of the administrative domain to
which the routing instance belongs. The as-data fields is used
when the routes in this instance are to be tagged with certain
autonomous system (AS) characteristics. The RIB manager can use
AS length as one of the parameters for making route selection. as-
data consists of a AS number and an optional Confederation AS
number ([RFC5065]).
2.3. Route
A route is essentially a match condition and an action following the
match. The match condition specifies the kind of route (IPv4, MPLS,
etc.) and the set of fields to match on. Figure 2 represents the
overall contents of a route.
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artwork
route
| | |
+---------+ | +----------+
| | |
0..N | | | 0..N
route-attributes match nexthop-list
|
|
+-------+-------+-------+--------+
| | | | |
| | | | |
IPv4 IPv6 MPLS MAC Interface
Figure 2: Route model
This document specifies the following match types:
o IPv4: Match on destination IP in IPv4 header
o IPv6: Match on destination IP in IPv6 header
o MPLS: Match on a MPLS tag
o MAC: Match on ethernet destination addresses
o Interface: Match on incoming interface of packet
o IP multicast: Match on (S, G) or (*, G), where S and G are IP
prefixes
Each route can have associated with it one or more optional route
attributes.
o ROUTE_PREFERENCE: This is a numerical value that allows for
comparing routes from different protocols (where static
configuration is also considered a protocol for the purpose of
this field). It is also known as administrative-distance. The
lower the value, the higher the preference. For example there can
be an OSPF route for 192.0.2.1/32 with a preference of 5. If a
controller programs a route for 192.0.2.1/32 with a preference of
2, then the controller entered route will be preferred by the RIB
manager. Preference should be used to dictate behavior. For more
examples of preference, see Section 7.1.
o ROUTE_METRIC: Route preference is used for comparing routes from
different protocols. Route metric is used for comparing routes
learned by the same protocol. If a controller wishes to program 2
or more routes to the same destination, then it can use the metric
field to disambiguate the 2 routes. For more examples, see
Section 7.1.
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o LOCAL_ONLY: This is a boolean value. If this is present, then it
means that this route should not be exported into other RIBs or
other RIBs.
o rpf-check-interface: Reverse path forwarding (RPF) check is used
to prevent spoofing and limit malicious traffic. For IP packets,
the IP source address is looked up and the rpf-check-interface
associated with the route for that IP source address is found. If
the incoming IP packet's interface matches one of the rpf-check-
interfaces, then the IP packet is forwarded based on its IP
destination address; otherwise, the IP packet is discarded. For
MPLS routes, there is no source address to be looked up, so the
usage is slightly different. For an MPLS route, a packet with the
specified MPLS label will only be forwarded if it is received on
one of the interfaces specified by the rpf-check-interface. If no
rpf-check-interface is specified, then matching packets are no
subject to this check. This field overrides the
ENABLE_IP_RPF_CHECK flag on the RIB and interfaces provided in
this list are used for doing the RPF check.
o as-path: A route can have an as-path associated with it to
indicate which set of autonomous systems has to be traversed to
reach the final destination. The as-path attribute can be used by
the RIB manager in multiple ways. The RIB manager can choose
paths with lower as-path length. Or the RIB manager can choose to
not install paths going via a particular AS. How exactly the RIB
manager uses the as-path is outside the scope of this document.
For details of how the as-path is formed, see Section 5.1.2 of
[RFC4271] and Section 3 of [RFC5065].
o route-vendor-attributes: Vendors can specify vendor-specific
attributes using this. The details of this field is outside the
scope of this document.
2.4. Nexthop
A nexthop represents an object or action resulting from a route
lookup. For example, if a route lookup results in sending the packet
out a given interface, then the nexthop represents that interface.
Nexthops can be fully resolved nexthops or unresolved nexthop. A
resolved nexthop is something that is ready for installation in the
FIB. For example, a nexthop that points to an interface. An
unresolved nexthop is something that requires the RIB manager to
figure out the final resolved nexthop. For example, a nexthop could
point to an IP address. The RIB manager has to resolve how to reach
that IP address - is the IP address reachable by regular IP
forwarding or by a MPLS tunnel or by both. If the RIB manager cannot
resolve the nexthop, then the nexthop stays in unresolved state and
is NOT a candidate for installation in the FIB. Future RIB events
can cause a nexthop to get resolved (like that IP address being
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advertised by an IGP neighbor).
The RIB information model allows an external entity to program
nexthops that may be unresolved initially. Whenever a unresolved
nexthop gets resolved, the RIB manager will send a notification of
the same (see Section 5 ).
The overall structure and usage of a nexthop is as shown in the
figure below.
route
|
| 0..N
nexthop-list
|
+------------------+------------------+
1..N | |
| |
nexthop-list-member special-nexthop
|
|
nexthop-chain
|
1..N |
nexthop
|
+------- nexthop-attributes
|
|
+--------+------+------------------+------------------+
| | | |
| | | |
nexthop-id egress-interface logical-tunnel tunnel-encap
Nexthops can be identified by an identifier to create a level of
indirection. The identifier is set by the RIB manager and returned
to the external entity on request. The RIB data-model SHOULD support
a way to optionally receive a nexthop identifier for a given nexthop.
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For example, one can create a nexthop that points to a BGP peer. The
returned nexthop identifier can then be used for programming routes
to point to the same nexthop. Given that the RIB manager has created
an indirection for that BGP peer using the nexthop identifier, if the
transport path to the BGP peer changes, that change in path will be
seamless to the external entity and all routes that point to that BGP
peer will automatically start going over the new transport path.
Nexthop indirection using identifier could be applied to not just
unicast nexthops, but even to nexthops that contain chains and nested
nexthops (Section 2.4.1).
2.4.1. Nexthop types
This document specifies a very generic, extensible and recursive
grammar for nexthops. Nexthops can be
o Unicast nexthops - pointing to an interface
o Tunnel nexthops - pointing to a tunnel
o Replication lists - list of nexthops to which to replicate a
packet to
o Weighted lists - for load-balancing
o Protection lists - for primary/backup paths
o Nexthop chains - for chaining headers, e.g. MPLS label over a GRE
header
o Lists of lists - recursive application of the above
o Indirect nexthops - pointing to a nexthop identifier
o Special nexthops - for performing specific well-defined functions
It is expected that all network devices will have a limit on how many
levels of lookup can be performed and not all hardware will be able
to support all kinds of nexthops. RIB capability negotiation becomes
very important for this reason and a RIB data-model MUST specify a
way for an external entity to learn about the network device's
capabilities. Examples of when and how to use various kinds of
nexthops are shown in Section 7.2.
Tunnel nexthops allow an external entity to program static tunnel
headers. There can be cases where the remote tunnel end-point does
not support dynamic signaling (e.g. no LDP support on a host) and in
those cases the external entity might want to program the tunnel
header on both ends of the tunnel. The tunnel nexthop is kept
generic with specifications provided for some commonly used tunnels.
It is expected that the data-model will model these tunnel types with
complete accuracy.
Nexthop chains can be used to specify multiple headers over a packet,
before a packet is forwarded. One simple example is that of MPLS
over GRE, wherein the packet has a inner MPLS header followed by a
GRE header followed by an IP header. The outermost IP header is
decided by the network device whereas the MPLS header and GRE header
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are specified by the controller. Not every network device will be
able to support all kinds of nexthop chains and an arbitrary number
of header chained together. The RIB data-model SHOULD provide a way
to expose nexthop chaining capability supported by a given network
device.
2.4.2. Nexthop list attributes
For nexthops that are of the form of a list(s), attributes can be
associated with each member of the list to indicate the role of an
individual member of the list. Two kinds of attributes are
specified:
o PROTECTION_PREFERENCE: This provides a primary/backup like
preference. The preference is an integer value that should be set
to 1 or 2. Nexthop members with a preference of 1 are preferred
over those with preference of 2. The network device SHOULD create
a list of nexthops with preference 1 (primary) and another list of
nexthops with preference 2 (backup) and SHOULD pre-program the
forwarding plane with both the lists. In case if all the primary
nexthops fail, then traffic MUST be switched over to members of
the backup nexthop list. All members in a list MUST either have a
protection preference specified or all members in a list MUST NOT
have a protection preference specified.
o LOAD_BALANCE_WEIGHT: This is used for load-balancing. Each list
member MUST be assigned a weight. The weight is a percentage
number from 1 to 99. The weight determines how much traffic is
sent over a given list member. If one of the members nexthops in
the list is not active, then the weight value of that nexthop
SHOULD be distributed among the other active members. How the
distribution is done is up to the network device and not in the
scope of the document. In other words, traffic should always be
load-balanced even if there is a failure. After a failure, the
external entity SHOULD re-program the nexthop list with updated
weights so as to get a deterministic behavior among the remaining
list members. To perform equal load-balancing, one MAY specify a
weight of "0" for all the member nexthops. The value "0" is
reserved for equal load-balancing and if applied, MUST be applied
to all member nexthops.
A nexthop list MAY contain elements that have both
PROTECTION_PREFERENCE and LOAD_BALANCE_WEIGHT set. When both are
set, it means under normal operation the network device should load
balance the traffic over all nexthops with a protection preference of
1. And when all nexthops with a protection preference of 1 are down
(or unavailable), then traffic MUST be load balanced over elements
with protection preference of 2.
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2.4.3. Nexthop content
At the lowest level, a nexthop can point to a:
o identifier: This is an identifier returned by the network device
representing another nexthop or another nexthop chain.
o EGRESS_INTERFACE: This represents a physical, logical or virtual
interface on the network device.
o address: This can be an IP address or MAC address or ISO address.
* An optional RIB name can also be specified to indicate the RIB
in which the address is to be looked up further. One can use
the RIB name field to direct the packet from one domain into
another domain. For example, a MPLS packet coming in on an
interface would be looked up in a MPLS RIB and the nexthop for
that could indicate that we strip the MPLS label and do a
subsequent IPv4 lookup in an IPv4 RIB. By default the RIB will
be the same in which the route lookup was performed.
* An optional egress interface can be specified to indicate which
interface to send the packet out on. The egress interface is
useful when the network device contains Ethernet interfaces and
one needs to perform an ARP lookup for the IP packet.
o tunnel encap: This can be an encap representing an IP tunnel or
MPLS tunnel or others as defined in this document. An optional
egress interface can be specified to indicate which interface to
send the packet out on. The egress interface is useful when the
network device contains Ethernet interfaces and one needs to
perform an ARP lookup for the IP packet.
o logical tunnel: This can be a MPLS LSP or a GRE tunnel (or others
as defined in this document), that is represented by a unique
identifier (E.g. name).
o RIB_NAME: A nexthop pointing to a RIB indicates that the route
lookup needs to continue in the specified RIB. This is a way to
perform chained lookups.
2.4.4. Nexthop attributes
Certain information is encoded implicitly in the nexthop and does not
need to be specified by the controller. For example, when a IP
packet is forwarded out, the IP TTL is decremented by default. Same
applies for an MPLS packet. Similarly, when an IP packet is sent
over an ethernet interface, any ARP processing is handled implicitly
by the network device and does not need to be programmed by an
external device.
A nexthop can have some attributes associated with it. The purpose
of the attributes is to either override implicit behavior (like that
related to TTL processing) or to guide the network device to perform
something specific. Vendor specific attributes can also be
specified. The details of vendor specific attributes is outside the
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scope of this document.
2.4.4.1. Nexthop flags
Nexthop flags in a nexthop is an optional attribute that is used to
denote specific connotation to hardware. Two common types of
operations are specified using nexthop flags.
o NO_DECREMENT_TTL: This indicates that the IPv4 time-to-live field
in an IPv4 packet MUST NOT be decremented before the packet is
forwarded. This may be applied one when an IPv4 packet is
encapsulated in a tunnel (E.g. MPLS) and one wants to hide the
fact that the packet is going through a tunnel.
o NO_PROPAGATE_TTL: This indicates that the IPv4 time-to-live field
in an IPv4 packet MUST NOT be propagated into an equivalent field,
when the IPv4 packet is tunneled. For example, if the IPv4 packet
is tunneled over MPLS, then the network device should use the
default time-to-live value for the outer MPLS header. This field
can also be used to indicate that when a tunnel terminates, one
does not propagate the outer header's time-to-live value into the
inner header. So, on MPLS tunnel termination, one does not
propagate the MPLS TTL value into the IPv4 header.
The TTL nexthop flags can be used to simulate a Pipe model for
tunnels. See [RFC3443] for a detailed understanding of Pipe model
and Uniform model.
2.4.5. Nexthop vendor attributes
This field has been defined for vendor specific extensions. The
contents of this field are beyond the scope of this document.
2.4.6. Special nexthops
This document specifies certain special nexthops. The purpose of
each of them is explained below:
o DISCARD: This indicates that the network device should drop the
packet and increment a drop counter.
o DISCARD_WITH_ERROR: This indicates that the network device should
drop the packet, increment a drop counter and send back an
appropriate error message (like ICMP error).
o RECEIVE: This indicates that that the traffic is destined for the
network device. For example, protocol packets or OAM packets.
All locally destined traffic SHOULD be throttled to avoid a denial
of service attack on the router's control plane. An optional
rate-limiter can be specified to indicate how to throttle traffic
destined for the control plane. The description of the rate-
limiter is outside the scope of this document.
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3. Reading from the RIB
A RIB data-model MUST allow an external entity to read entries, for
RIBs created by that entity. The network device administrator MAY
allow reading of other RIBs by an external entity through access
lists on the network device. The details of access lists are outside
the scope of this document.
The data-model MUST support a full read of the RIB and subsequent
incremental reads of changes to the RIB. An external agent SHOULD be
able to request a full read at any time in the lifecycle of the
connection. When sending data to an external entity, the RIB manager
SHOULD try to send all dependencies of an object prior to sending
that object.
4. Writing to the RIB
A RIB data-model MUST allow an external entity to write entries, for
RIBs created by that entity. The network device administrator MAY
allow writes to other RIBs by an external entity through access lists
on the network device. The details of access lists are outside the
scope of this document.
When writing an object to a RIB, the external entity SHOULD try to
write all dependencies of the object prior to sending that object.
The data-model MUST support requesting identifiers for nexthops and
collecting the identifiers back in the response.
Route programming in the RIB MUST result in a return code that
contains the following attributes:
o Installed - Yes/No (Indicates whether the route got installed in
the FIB)
o Active - Yes/No (Indicates whether a route is fully resolved and
is a candidate for selection)
o Reason - E.g. Not authorized
The data-model MUST specify which objects are modify-able objects. A
modify-able object is one whose contents can be changed without
having to change objects that depend on it and without affecting any
data forwarding. To change a non-modifiable object, one will need to
create a new object and delete the old one. For example, routes that
use a nexthop that is identifier by a nexthop-identifier should be
unaffected when the contents of that nexthop changes.
5. Events and Notifications
Asynchronous notifications are sent by the network device's RIB
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manager to an external entity when some event occurs on the network
device. A RIB data-model MUST support sending asynchronous
notifications. A brief list of suggested notifications is as below:
o Route change notification, with return code as specified in
Section 4
o Nexthop resolution status (resolved/unresolved) notification
6. RIB grammar
This section specifies the RIB information model in Routing Backus-
Naur Form [RFC5511].
<routing-instance> ::= <INSTANCE_NAME> <INSTANCE_DISTINGUISHER>
[<interface-list>] <rib-list>
[<ROUTER_ID>] [<as-data>]
<as-data> ::= <AS_NUMBER> [<CONFEDERATION_AS>]
<interface-list> ::= (<INTERFACE_IDENTIFIER> ...)
<rib-list> ::= (<rib> ...)
<rib> ::= <RIB_NAME> <rib-family>
[<route> ... ] [<MULTI_TOPOLOGY_ID>]
[ENABLE_IP_RPF_CHECK]
<rib-family> ::= <IPV4_RIB_FAMILY> | <IPV6_RIB_FAMILY> |
<MPLS_RIB_FAMILY> | <IEEE_MAC_RIB_FAMILY>
<route> ::= <match> <nexthop-list>
[<route-attributes>]
[<route-vendor-attributes>]
<match> ::= <ipv4-route> | <ipv6-route> | <mpls-route> |
<mac-route> | <interface-route>
<ipv4-route> ::= <ipv4-prefix> [<multicast-source-ipv4-address>]
<ipv4-prefix> ::= <IPV4_ADDRESS> <IPV4_ADDRESS_LENGTH>
<ipv6-route> ::= <ipv6-prefix> [<multicast-source-ipv6-address>]
<ipv6-prefix> ::= <IPV6_ADDRESS> <IPV6_PREFIX_LENGTH>
<mpls-route> ::= <MPLS> <MPLS_LABEL>
<mac-route> ::= <IEEE_MAC> ( <MAC_ADDRESS> )
<interface-route> ::= <INTERFACE> <INTERFACE_IDENTIFIER>
<multicast-source-ipv4-address> ::= <IPV4_ADDRESS>
<IPV4_PREFIX_LENGTH>
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<multicast-source-ipv6-address> ::= <IPV6_ADDRESS>
<IPV6_PREFIX_LENGTH>
<route-attributes> ::= [<ROUTE_PREFERENCE>] [<ROUTE_METRIC>]
[<LOCAL_ONLY>]
[<address-family-route-attributes>]
<address-family-route-attributes> ::= <ip-route-attributes> |
<mpls-route-attributes> |
<ethernet-route-attributes>
<ip-route-attributes> ::= [<as-path>] [<rpf-check-interface>]
<as-path> ::= (<as-path-segment-type> <as-list>) [<as-path> ...]
<as-path-segment-type> ::= <AS_SET> | <AS_SEQUENCE> |
<AS_CONFED_SEQUENCE> | <AS_CONFED_SET>
<as-list> ::= (<AS_NUMBER> ...) [<as-path>]
<rpf-check-interface> ::= <interface-list>
<mpls-route-attributes> ::= [<rpf-check-interface>]
<ethernet-route-attributes> ::= <>
<route-vendor-attributes> ::= <>
<nexthop-list> ::= <special-nexthop> |
((<nexthop-list-member>) |
([<nexthop-list-member> ... ] <nexthop-list> ))
<nexthop-list-member> ::= (<nexthop-chain> |
<nexthop-chain-identifier> )
[<nexthop-list-member-attributes>]
<nexthop-list-member-attributes> ::= [<PROTECTION_PREFERENCE>]
[<LOAD_BALANCE_WEIGHT>]
<nexthop-chain> ::= (<nexthop> ...)
<nexthop-chain-identifier> ::= <NEXTHOP_NAME> | <NEXTHOP_ID>
<nexthop> ::= (<nexthop-identifier> | <EGRESS_INTERFACE> |
(<nexthop-address>
([<RIB_NAME>] | [<EGRESS_INTERFACE>])) |
(<tunnel-encap> [<EGRESS_INTERFACE>]) |
<logical-tunnel> |
<RIB_NAME>)
[<nexthop-attributes>]
[<nexthop-vendor-attributes>]
<nexthop-identifier> ::= <NEXTHOP_NAME> | <NEXTHOP_ID>
<nexthop-address> ::= (<IPv4> <ipv4-address>) |
(<IPV6> <ipv6-address>) |
(<IEEE_MAC> <IEEE_MAC_ADDRESS>) |
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(<ISO> <ISO_ADDRESS>)
<special-nexthop> ::= <DISCARD> | <DISCARD_WITH_ERROR> |
(<RECEIVE> [<COS_VALUE>] [<rate-limiter>])
<rate-limiter> ::= <>
<logical-tunnel> ::= <tunnel-type> <TUNNEL_NAME>
<tunnel-type> ::= <IP> | <MPLS> | <GRE> | <VxLAN> | <NVGRE>
<tunnel-encap> ::= (<IPV4> <ipv4-header>) |
(<IPV6> <ipv6-header>) |
(<MPLS> <mpls-header>) |
(<GRE> <gre-header>) |
(<VXLAN> <vxlan-header>) |
(<NVGRE> <nvgre-header>)
<ipv4-header> ::= <SOURCE_IPv4_ADDRESS> <DESTINATION_IPv4_ADDRESS>
<PROTOCOL> [<TTL>] [<DSCP>]
<ipv6-header> ::= <SOURCE_IPV6_ADDRESS> <DESTINATION_IPV6_ADDRESS>
<NEXT_HEADER> [<TRAFFIC_CLASS>]
[<FLOW_LABEL>] [<HOP_LIMIT>]
<mpls-header> ::= (<mpls-label-operation> ...)
<mpls-label-operation> ::= (<MPLS_PUSH> <MPLS_LABEL> [<S_BIT>]
[<TOS_VALUE>] [<TTL_VALUE>]) |
(<MPLS_POP> [<TTL_ACTION>])
<gre-header> ::= <GRE_IP_DESTINATION> <GRE_PROTOCOL_TYPE> [<GRE_KEY>]
<vxlan-header> ::= (<ipv4-header> | <ipv6-header>)
[<VXLAN_IDENTIFIER>]
<nvgre-header> ::= (<ipv4-header> | <ipv6-header>)
<VIRTUAL_SUBNET_ID>
[<FLOW_ID>]
<nexthop-attributes> ::= [<NEXTHOP_ADDRESS_FAMILY>]
[<nexthop-flags>]
<NEXTHOP_ADDRESS_FAMILY> ::= <IPV4> | <IPV6> | <ISO> | <IEEE MAC>
<nexthop-flags> ::= [<NO_DECREMENT_TTL>] [<NO_PROPAGATE_TTL>]
<nexthop-vendor-attributes> ::= <>
7. Using the RIB grammar
The RIB grammar is very generic and covers a variety of features.
This section provides examples on using objects in the RIB grammar
and examples to program certain use cases.
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7.1. Using route preference and metric
Using route preference one can pre-install protection paths in the
network. For example, if OSPF has a route preference of 10, then one
can install a route with route preference of 20 to the same
destination. The OSPF route will get precedence and will get
installed in the FIB. When the OSPF route goes away (for any
reason), the protection path will get installed in the FIB. If the
hardware supports it, then the RIB manager can choose to pre-install
both routes, with the OSPF nexthop getting preference.
Route preference can also be used to prevent denial of service
attacks by installing routes with the best preference, which either
drops the offending traffic or routes it to some monitoring/analysis
station. Since the routes are installed with the best preference,
they will supersede any route installed by any other protocol.
Route metric is used to disambiguate between 2 or more routes to the
same destination with the same preference and in the same RIB. One
usage of this is to install 2 routes, each with a different nexthop.
The preferred nexthop is given a better metric than the other one.
This results in traffic being forwarded to the preferred nexthop. If
the preferred nexthop fails, then the RIB manager will automatically
install a route to the other nexthop.
7.2. Using different nexthops types
The RIB grammar allows one to create a variety of nexthops. This
section describes uses for certain types of nexthops.
7.2.1. Tunnel nexthops
A tunnel nexthop points to a tunnel of some kind. Traffic that goes
over the tunnel gets encapsulated with the tunnel encap. Tunnel
nexthops are useful for abstracting out details of the network, by
having the traffic seamlessly route between network edges.
7.2.2. Replication lists
One can create a replication list for replication traffic to multiple
destinations. The destinations, in turn, could be complex nexthops
in themselves - at a level supported by the network device. Point to
multipoint and broadcast are examples that involve replication.
A replication list (at the simplest level) can be represented as:
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<nexthop-list> ::= <nexthop> [ <nexthop> ... ]
The above can be derived from the grammar as follows:
<nexthop-list> ::= <nexthop-list-member> [<nexthop-list-member> ...]
<nexthop-list> ::= <nexthop-chain> [<nexthop-chain> ...]
<nexthop-list> ::= <nexthop> [ <nexthop> ... ]
7.2.3. Weighted lists
A weighted list is used to load-balance traffic among a set of
nexthops. From a modeling perspective, a weighted list is very
similar to a replication list, with the difference that each member
nexthop MUST have a LOAD_BALANCE_WEIGHT associated with it.
A weighted list (at the simplest level) can be represented as:
<nexthop-list> ::= (<nexthop> <LOAD_BALANCE_WEIGHT>)
[(<nexthop> <LOAD_BALANCE_WEIGHT>)... ]
The above can be derived from the grammar as follows:
<nexthop-list> ::= <nexthop-list-member> [<nexthop-list-member> ...]
<nexthop-list> ::= (<nexthop-chain> <nexthop-list-member-attributes>)
[(<nexthop-chain>
<nexthop-list-member-attributes>) ...]
<nexthop-list> ::= (<nexthop-chain> <LOAD_BALANCE_WEIGHT>)
[(<nexthop-chain> <LOAD_BALANCE_WEIGHT>) ... ]
<network-list> ::= (<nexthop> <LOAD_BALANCE_WEIGHT>)
[(<nexthop> <LOAD_BALANCE_WEIGHT>)... ]
7.2.4. Protection lists
Protection lists are similar to weighted lists. A protection list
specifies a set of primary nexthops and a set of backup nexthops.
The <PROTECTION_PREFERENCE> attribute indicates which nexthop is
primary and which is backup.
A protection list can be represented as:
<nexthop-list> ::= (<nexthop> <PROTECTION_PREFERENCE>)
[(<nexthop> <PROTECTION_PREFERENCE>)... ]
A protection list can also be a weighted list. In other words,
traffic can be load-balanced among the primary nexthops of a
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protection list. In such a case, the list will look like:
<nexthop-list> ::= (<nexthop> <PROTECTION_PREFERENCE>
<LOAD_BALANCE_WEIGHT>)
[(<nexthop> <PROTECTION_PREFERENCE>
<LOAD_BALANCE_WEIGHT>)... ]
7.2.5. Nexthop chains
A nexthop chain is a nexthop that puts one or more headers on an
outgoing packet. One example is a Pseudowire - which is MPLS over
some transport (MPLS or GRE for instance). Another example is VxLAN
over IP. A nexthop chain allows an external entity to break up the
programming of the nexthop into independent pieces - one per
encapsulation.
A simple example of MPLS over GRE can be represented as:
<nexthop-list> ::= (<MPLS> <mpls-header>) (<GRE> <gre-header>)
The above can be derived from the grammar as follows:
<nexthop-list> ::= <nexthop-list-member> [<nexthop-list-member> ...]
<nexthop-list> ::= <nexthop-chain>
<nexthop-list> ::= <nexthop> [ <nexthop> ... ]
<nexthop-list> ::= <tunnel-encap> (<nexthop> [ <nexthop> ...])
<nexthop-list> ::= <tunnel-encap> (<tunnel-encap>)
<nexthop-list> ::= (<MPLS> <mpls-header>) (<GRE> <gre-header>)
7.2.6. Lists of lists
Lists of lists is a complex construct. One example of usage of such
a construct is to replicate traffic to multiple destinations, with
high availability. In other words, for each destination you have a
primary and backup nexthop (replication list) to ensure there is no
traffic drop in case of a failure. So the outer list is a protection
list and the inner lists are replication lists of primary/backup
nexthops.
7.3. Performing multicast
IP multicast involves matching a packet on (S, G) or (*, G), where
both S (source) and G (group) are IP prefixes. Following the match,
the packet is replicated to one or more recipients. How the
recipients subscribe to the multicast group is outside the scope of
this document.
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In PIM-based multicast, the packets are IP forwarded on an IP
multicast tree. The downstream nodes on each point in the multicast
tree is one or more IP addresses. These can be represented as a
replication list ( Section 7.2.2 ).
In MPLS-based multicast, the packets are forwarded on a point to
multipoint (P2MP) label-switched path (LSP). The nexthop for a P2MP
LSP can be represented in the nexthop grammar as a <logical-tunnel>
(P2MP LSP identifier) or a replication list ( Section 7.2.2) of
<tunnel-encap>, with each tunnel encap representing a single mpls
downstream nexthop.
7.4. Solving optimized exit control
In case of optimized exit control, a controller wants to control the
edge device (and optionally control the outgoing interface on that
edge device) that is used by a server to send traffic out. This can
be easily achieved by having the controller program the edge router
(Eg. 192.0.2.10) and the server along the following lines:
Server:
<route> ::= <rib-name> <match> (<edge-router>
<edge-router-interface>)
<route> ::= <rib-name> <198.51.100.1/16>
(<MPLS> <mpls-header>)
(<GRE> <gre-header>)
<route> ::- <rib-name> <198.51.100.1/16>
(<MPLS_PUSH> <100>)
(<GRE> <192.0.2.10> <GRE_PROTOCOL_MPLS>)
Edge Router:
<route> ::= <mpls-rib> <mpls-route> <nexthop>
<route> ::= <mpls-rib> (<MPLS> <100>) <interface-10>
In the above case, the label 100 identifies the egress interface
on the edge router.
8. RIB operations at scale
This section discusses the scale requirements for a RIB data-model.
The RIB data-model should be able to handle large scale of
operations, to enable deployment of RIB applications in large
networks.
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8.1. RIB reads
Bulking (grouping of multiple objects in a single message) MUST be
supported when a network device sends RIB data to an external entity.
Similarly the data model MUST enable a RIB client to request data in
bulk from a network device.
8.2. RIB writes
Bulking (grouping of multiple write operations in a single message)
MUST be supported when an external entity wants to write to the RIB.
The response from the network device MUST include a return-code for
each write operation in the bulk message.
8.3. RIB events and notifications
There can be cases where a single network event results in multiple
events and/or notifications from the network device to an external
entity. On the other hand, due to timing of multiple things
happening at the same time, a network device might have to send
multiple events and/or notifications to an external entity. The
network device originated event/notification message MUST support
bulking of multiple events and notifications in a single message.
9. Security Considerations
All interactions between a RIB manager and an external entity MUST be
authenticated and authorized. The RIB manager MUST protect itself
against a denial of service attack by a rogue external entity, by
throttling request processing. A RIB manager MUST enforce limits on
how much data can be programmed by an external entity and return
error when such a limit is reached.
The RIB manager MUST expose a data-model that it implements. An
external agent MUST send requests to the RIB manager that comply with
the supported data-model. The data-model MUST specify the behavior
of the RIB manager on handling of unsupported data requests.
10. IANA Considerations
This document does not generate any considerations for IANA.
11. Acknowledgements
The authors would like to thank the working group co-chairs and
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reviewers on their comments and suggestions on this draft. The
following people contributed to the design of the RIB model as part
of the I2RS Interim meeting in April 2013 - Wes George, Chris
Liljenstolpe, Jeff Tantsura, Sriganesh Kini, Susan Hares, Fabian
Schneider and Nitin Bahadur.
12. References
12.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
12.2. Informative References
[I-D.atlas-i2rs-problem-statement]
Atlas, A., Nadeau, T., and D. Ward, "Interface to the
Routing System Problem Statement",
draft-atlas-i2rs-problem-statement-02 (work in progress),
August 2013.
[I-D.hares-i2rs-use-case-vn-vc]
Hares, S., "Use Cases for Virtual Connections on Demand
(VCoD) and Virtual Network on Demand using Interface to
Routing System", draft-hares-i2rs-use-case-vn-vc-00 (work
in progress), February 2013.
[I-D.white-i2rs-use-case]
White, R., Hares, S., and R. Fernando, "Use Cases for an
Interface to the Routing System",
draft-white-i2rs-use-case-00 (work in progress),
February 2013.
[RFC3443] Agarwal, P. and B. Akyol, "Time To Live (TTL) Processing
in Multi-Protocol Label Switching (MPLS) Networks",
RFC 3443, January 2003.
[RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
Protocol 4 (BGP-4)", RFC 4271, January 2006.
[RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P.
Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF",
RFC 4915, June 2007.
[RFC5065] Traina, P., McPherson, D., and J. Scudder, "Autonomous
System Confederations for BGP", RFC 5065, August 2007.
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[RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
Topology (MT) Routing in Intermediate System to
Intermediate Systems (IS-ISs)", RFC 5120, February 2008.
[RFC5511] Farrel, A., "Routing Backus-Naur Form (RBNF): A Syntax
Used to Form Encoding Rules in Various Routing Protocol
Specifications", RFC 5511, April 2009.
Authors' Addresses
Nitin Bahadur (editor)
Juniper Networks, Inc.
1194 N. Mathilda Avenue
Sunnyvale, CA 94089
US
Phone: +1 408 745 2000
Email: nitinb@juniper.net
URI: www.juniper.net
Ron Folkes (editor)
Juniper Networks, Inc.
1194 N. Mathilda Avenue
Sunnyvale, CA 94089
US
Phone: +1 408 745 2000
Email: ronf@juniper.net
URI: www.juniper.net
Sriganesh Kini
Ericsson
Email: sriganesh.kini@ericsson.com
Jan Medved
Cisco
Email: jmedved@cisco.com
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