Internet DRAFT - draft-boucadair-lisp-itr-failure
draft-boucadair-lisp-itr-failure
Network Working Group M. Boucadair
Internet-Draft C. Jacquenet
Intended status: Experimental Orange
Expires: April 18, 2018 October 15, 2017
Improving ITR Resiliency in Locator/ID Separation Protocol (LISP)
Networks
draft-boucadair-lisp-itr-failure-05
Abstract
This document defines an extension to the Locator/ID Separation
Protocol (LISP) to minimize LISP service disruption during Ingress
Tunnel Routers (ITRs) failure events.
Requirements Language
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 RFC 2119 [RFC2119].
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
Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 18, 2018.
Copyright Notice
Copyright (c) 2017 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
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publication of this document. Please review these documents
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carefully, as they describe your rights and restrictions with respect
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Map-Solicit-Request: Message Format & Behavior . . . . . . . 5
4. Map-Solicit-Reply: Message Format & Behavior . . . . . . . . 7
5. Security Considerations . . . . . . . . . . . . . . . . . . . 10
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
8.1. Normative references . . . . . . . . . . . . . . . . . . 10
8.2. Informative References . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
Locator/ID Separation Protocol (LISP, [RFC6830] ) operation relies
upon a mapping mechanism that is used by Ingress/Egress Tunnel
Routers (xTR) to forward traffic over the LISP network.
A reboot of an ITR may dramatically affect the LISP-based forwarding
service for hosts connected to the LISP network. Because of the
purge of the mapping cache maintained by the rebooting ITR, the
absence of a matching entry for packets to be forwarded over the LISP
network will simply cause the dropping of such packets, even though
other ITRs of the LISP domain may be "ready-to-serve".
An ITR that loses its local mapping table for some reason is very
likely to drop incoming packets whose forwarding decision relies upon
the entries of the local mapping table. This type of ITR failure may
rarely occur, but when it does, it is likely to provoke severe
service degradation.
This document proposes a solution to enhance the robustness of LISP
networks during such ITR failure events. This document assumes that
several ITRs are available within the LISP network. The solution
allows for an automatic discovery of the available ITRs of a given
LISP domain.
The approach exclusively focuses on engineering tweaks that can be
implemented within a LISP-enabled network without soliciting the help
of the LISP Mapping System. [I-D.boucadair-lisp-subscribe] is a
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companion document that specifies a procedure that is meant to
rapidly populate a local mapping cache upon restart or whenever
failures affect ITR operation.
2. Procedure
The overall procedure is as follows:
1. A dedicated IPv4 and/or IPv6 multicast address is reserved for
ITR resiliency (called @MCAST in this document). An address can
be reserved by an administrator for this purpose.
2. A list of unicast addresses of available ITRs in a given domain
is maintained by the requesting ITR (ITR-PEER-LIST).
3. When an ITR loses its mapping table for some reason (power
failure, software issue, etc.), but can still forward packets, it
checks whether it maintains a list of peer ITRs. If the peer ITR
list is empty, it sends a message, denoted Map-Solicit-Request
(Section 3), to @MCAST. If a list is available, the ITR follows
Steps (5, 6, and 7).
Note that the same IP address (@MCAST) is used to announce the
availability of an ITR within a LISP domain on a regular basis.
4. Once this message is received by another ITR reachable in the
LISP domain, it replies with a Map-Solicit-Reply (Section 4)
using its unicast address as the source IP address. The Map-
Solicit-Reply includes the following information:
* Database Status (including cache status). A status set to
'Null' indicates this ITR does not maintain any cache because,
e.g., it is a new ITR, it lost its mappings, etc.
* The content of local ITR-PEER-LIST: This is to accelerate the
process of discovering other ITRs within a LISP domain without
waiting for responses from other ITRs.
* Synchronisation reachability information (address, port
number, protocol, etc.)
5. Bulk mapping requests (e.g., [I-D.boucadair-lisp-bulk] or
[I-D.boucadair-lisp-multiple-records]) are then sent to peer ITRs
to retrieve a copy of their map cache. One or several ITRs can
be solicited simultaneously.
6. In the meantime, cache synchronisation is in progress, packets
that do not match a mapping entry are redirected to another ITR
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in the domain that has its database 'ready-to-serve'. These
packets are encapsulated in a LISP header using the unicast
address discovered in the previous steps.
7. A peer ITR decapsulates the packet, encapsulates it according to
the matching mapping entry, and forwards the encapsulated packet
towards the next hop. Moreover, it sends an unsolicited Map-
Reply to the original ITR so that it can handle locally
subsequent packets that belong to this flow.
The 'nonce' of the unsolicited Map-Reply must echo the one
included in the encapsulated packet received from the first ITR.
An indication to disable data gleaning may be included by the
relay ITR (e.g., using the extension defined in Section 3 of
[I-D.boucadair-lisp-ms-assisted-forwarding]).
Figure 1 illustrates an example of an ITR (ITR1) which encounters a
loss of its mapping cache. As a result, it generates a Map-Solicit-
Request that it sends to the multicast address @MCAST. Upon receipt
of that request by ITR2 and ITR3, they each reply with a Map-Solicit-
Reply message. The first reply is used by ITR1 to decide to which
peer ITR it will redirect packets during the failure event (ITR2).
These packets are encapsulated with a LISP header and forwarded to
ITR2. Once received by ITR2, these packets are forwarded to their
ultimate ETR. In the meantime, ITR2 generates an unsolicited Map-
Reply to inform ITR1 with the mapping entries related to the
destination EID. Subsequent packets that belong to this flow are
therefore handled locally by ITR1 without soliciting ITR2.
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+--------+ +--------+ +--------+ +--------+
| ITR1 | | ITR2 | | ITR3 | | ETR |
+--------+ +--------+ +--------+ +--------+
| | | |
|Map-Solicit-Request | | |
| to @MCAST | | |
|--------> | | |
| Map-Solicit-Reply| | |
|<--------------------------| | |
| Map-Solicit-Reply| |
|<-------------------------------------| |
src=s_EID| | |
-------->|src=RLOC_itr1 dst=RLOC_itr2| |
dst=d_EID|===Encapsulated Packet====>|src=RLOC_itr2 dst=RLOC_etr|src=s_EID
| Unsolicited Map-Reply |===Encapsulated Packet===>|-------->
|<--------------------------| |dst=d_EID
| |
src=s_EID| |
-------->|src=RLOC_itr1 dst=RLOC_etr|src=s_EID
dst=d_EID|===================Encapsulated Packet===============>|-------->
| |dst=d_EID
....
src=s_EID| |
-------->|src=RLOC_itr1 dst=RLOC_etr |src=s_EID
dst=d_EID|===================Encapsulated Packet===============>|-------->
| |dst=d_EID
Figure 1: Flow Example
3. Map-Solicit-Request: Message Format & Behavior
The format of the Map-Solicit-Request message is shown in Figure 2.
This format follows the LISP shared extension message defined in
[RFC8113].
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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=15| Sub-type |R|S|D| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Nonce . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| . . . Nonce |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Key ID | Authentication Data Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Authentication Data ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| IP Address (128 bits) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Port Number | Protocol | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Map-Solicit-Request Message Format
The description of the fields is as follows:
o Type MUST be set to 15 [RFC8113].
o sub-type: MUST be set to 1026.
o R: MUST be set to 0 for Map-Solicit-Request messages.
o S: when set, this flag indicates that the originating ITR supports
a mechanism for state synchronisation of the mapping cache between
ITRs. When this flag is set, the message MUST carry the port
number, protocol, and IP Address used for synchronisation
purposes. This specification allows to indicate a distinct IP
address for state synchronisation purposes.
o D: This flag indicates the status of the mapping cache table. It
is RECOMMENDED to set this flag to 1 when the ITR is up and
running for at least one hour and has a non-empty mapping cache.
An ITR that lost its state MUST set this flag to 0.
o Nonce, Key ID, Authentication Data Length, and Authentication Data
are similar to those of a LISP Map-Register message ([RFC6830]).
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o IP Address: If S-bit is set, this field indicates the IP address
used to receive state synchronisation messages. If S-bit is
unset, this field MUST be set to zero at the originating ITR and
MUST be ignored at receipt. The length of this field is 128 bits.
IPv4 addresses are encoded as IPv4-mapped IPv6 addresses [RFC4291]
(::ffff:0:0/96).
o Port Number: If the S-bit is set, this field indicates the port
number used to receive state synchronisation messages. If unset,
this field MUST be set to zero at the originating ITR and MUST be
ignored at receipt.
o Protocol: If the S-bit is set, this field indicates the protocol
used to transport state synchronisation messages. If unset, this
field MUST be set to zero at the originating ITR and MUST be
ignored upon receipt.
An ITR that issues this message MUST use one of its unicast IP
addresses as the source address. The destination IP address MUST be
set to the @MCAST multicast address introduced in Section 2. An ITR
that loses its cache MUST issue this message with a D-bit set to 0.
4. Map-Solicit-Reply: Message Format & Behavior
All ITRs of a LISP domain MUST subscribe to the multicast group
defined by the aforementioned @MCAST multicast address.
Upon receipt of the Map-Solicit-Request message by an ITR within the
domain, it replies (unicast) with a Map-Solicit-Reply. It is the
responsibility of the first ITR to initiate a state synchronisation
with that peer if the D-bit and S-bit are unset and if it supports
the synchronisation protocol indicated in the Map-Solicit-Reply.
ITRs of a LISP domain MUST send Map-Solicit-Reply in a regular
interval (that is configured by an administrator) or upon major
change in the ITR stats (e.g., loss of the mapping cache, change of
the IP address). This message MUST use one of the ITR unicast IP
addresses as the source address while the destination IP address MUST
be set to the @MCAST.
The format of the Map-Solicit-Reply message is shown in Figure 3.
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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=15| Sub-type |R|S|D| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Nonce . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| . . . Nonce |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Key ID | Authentication Data Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Authentication Data ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| IP Address (128 bits) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Port Number |Protocol |ITR List Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Peer ITR Unicast Address |
| (128 bits) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Peer ITR Unicast Address |
| (128 bits) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Map-Solicit-Reply Message Format
The description of the fields is as follows:
o Type MUST be set to 15 [RFC8113].
o sub-type: MUST be set to 1026.
o R: MUST be set to 1.
o S: when set, this flag indicates that the originating ITR supports
a mechanism for state synchronisation of the mapping caches
between ITRs. When set, the message MUST carry the port number,
protocol, and IP Address used for synchronisation purposes. This
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specification allows to indicate a distinct IP address for state
synchronisation purposes.
o D: This flag indicates the status of the mapping cache table. It
is RECOMMENDED to set this flag when the ITR is up and running for
at least one hour and has a non-empty mapping cache.
o Nonce: The 'Nonce' field of multicast Map-Solicit-Reply MUST be
set to 0 while it MUST echo the one included in a Map-Solicit-
Request when replying to a multicast Map-Solicit-Request.
o Key ID, Authentication Data Length, and Authentication Data are
similar to those of a LISP Map-Register message ([RFC6830]).
o IP Address: If the S-bit is set, this field indicates the IP
address used to receive state synchronisation messages. If unset,
this field MUST be set to zero at the originating ITR and MUST be
ignored upon receipt. The length of this field is 128 bits. IPv4
addresses are encoded as IPv4-mapped IPv6 addresses [RFC4291]
(::ffff:0:0/96).
o Port Number: If the S-bit is set, this field indicates the port
number used to receive state synchronisation messages. If unset,
this field MUST be set to zero at the originating ITR and MUST be
ignored upon receipt.
o Protocol: If the S-bit is set, this field indicates the protocol
used to transport state synchronisation messages. If unset, this
field MUST be set to zero at the originating ITR and MUST be
ignored upon receipt.
o ITR List Count: This field indicates whether peer ITR addresses
are also included. When this field is set to 0, it indicates that
no peers other than the solicited peer ITR are known to the
originating ITR.
o Peer ITR Unicast Address: one or multiple IP addresses that belong
to other ITRs in the domain as known to the originating ITR. The
length of each "Peer ITR Unicast Address" is 128 bits. IPv4
addresses are encoded as IPv4-mapped IPv6 addresses
(::ffff:0:0/96).
A Map-Solicit-Reply can be generated by an ITR to advertise its
availability to the other ITRs of the LISP domain, as per normal LISP
operation.
When an ITR receives a LISP-encapsulated packet from an ITR that is
present in its list of peer ITRs, it may generate an unsolicited Map-
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Reply that conveys the mapping entry that was used to process the
encapsulated packet.
Upon failure or reboot that lead to lose the contents of its mapping
cache, an ITR uses the list of peers ITRs it discovered by means of
the Map-Solicit-Request message sent to @MCAST to redirect packets
that do not match any entry of its local cache (which is likely to be
empty).
In order to minimize the risk of overloading some ITRs, a mechanism
to distribute the load among all the peer ITRs or part of them is
deemed useful. Of course, other traffic load distribution policies
may be enforced. The exact set of policies to be enforced are
implementation- and deployment-specific.
5. Security Considerations
LISP security considerations are discussed in [RFC6830].
This document specifies a mechanism that enhances the serviceability
of LISP networks by redirecting traffic that do not match a local
mapping entry to other ITRs of the domain. These ITRs are assumed to
belong to the same administrative domain. Means to ensure that only
trusted ITRs are maintained in a peer list MUST be enabled.
6. IANA Considerations
IANA has assigned the following code from the LISP Shared Extension
Message Type Sub-types ([RFC8113]):
Message Sub-type Reference
===================================== ======= ===============
Map-Solicit-Request/Map-Solicit-Reply 1026 [This document]
7. Acknowledgments
This work is partly funded by ANR LISP-Lab project #ANR-13-INFR-
009-X.
Many thanks to Chi Dung Phung for the review.
8. References
8.1. Normative references
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, DOI 10.17487/RFC4291, February
2006, <https://www.rfc-editor.org/info/rfc4291>.
[RFC6830] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The
Locator/ID Separation Protocol (LISP)", RFC 6830,
DOI 10.17487/RFC6830, January 2013,
<https://www.rfc-editor.org/info/rfc6830>.
[RFC8113] Boucadair, M. and C. Jacquenet, "Locator/ID Separation
Protocol (LISP): Shared Extension Message & IANA Registry
for Packet Type Allocations", RFC 8113,
DOI 10.17487/RFC8113, March 2017,
<https://www.rfc-editor.org/info/rfc8113>.
8.2. Informative References
[I-D.boucadair-lisp-bulk]
Boucadair, M. and C. Jacquenet, "LISP Mapping Bulk
Retrieval", draft-boucadair-lisp-bulk-05 (work in
progress), April 2017.
[I-D.boucadair-lisp-ms-assisted-forwarding]
Boucadair, M. and C. Jacquenet, "Mapping System-Assisted
Forwarding for Inter-Domain LISP Deployments", draft-
boucadair-lisp-ms-assisted-forwarding-00 (work in
progress), September 2015.
[I-D.boucadair-lisp-multiple-records]
Boucadair, M. and C. Jacquenet, "Retrieving Multiple LISP
Records", draft-boucadair-lisp-multiple-records-00 (work
in progress), October 2017.
[I-D.boucadair-lisp-subscribe]
Boucadair, M. and C. Jacquenet, "LISP Subscription",
draft-boucadair-lisp-subscribe-05 (work in progress),
April 2017.
Authors' Addresses
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Mohamed Boucadair
Orange
Rennes 35000
France
EMail: mohamed.boucadair@orange.com
Christian Jacquenet
Orange
Rennes 35000
France
EMail: christian.jacquenet@orange.com
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