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Network Working Group                                       M. Boucadair
Internet-Draft                                              C. Jacquenet
Intended status: Experimental                                     Orange
Expires: August 7, 2017                                 February 3, 2017


   Improving ITR Resiliency in Locator/ID Separation Protocol (LISP)
                                Networks
                  draft-boucadair-lisp-itr-failure-03

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
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on August 7, 2017.

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
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents



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   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  . . . . . . . . . . . . . . . . . . . . . . . .   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]) are then
       sent to peer ITRs to retrieve a copy of their map cache.  One or
       several ITRs can be solicited.

   6.  In the meantime, cache synchronisation is in progress, packets
       that do not match a mapping entry are redirected to another ITR
       in the domain that has its database 'ready-to-serve'.  These



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       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
   [I-D.ietf-lisp-type-iana].

















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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 [I-D.ietf-lisp-type-iana].

   o  sub-type: MUST be set to 1024.

   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 stae 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 [I-D.ietf-lisp-type-iana].

   o  sub-type: MUST be set to 1024.

   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 serveiceabilty
   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

   To be completed.

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

   [I-D.ietf-lisp-type-iana]
              Boucadair, M. and C. Jacquenet, "LISP Shared Extension
              Message & IANA Registry for LISP Packet Type Allocations",
              draft-ietf-lisp-type-iana-06 (work in progress), February
              2017.






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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,
              <http://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, <http://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,
              <http://www.rfc-editor.org/info/rfc6830>.

8.2.  Informative References

   [I-D.boucadair-lisp-bulk]
              Boucadair, M. and C. Jacquenet, "LISP Mapping Bulk
              Retrieval", draft-boucadair-lisp-bulk-03 (work in
              progress), July 2016.

   [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-subscribe]
              Boucadair, M. and C. Jacquenet, "LISP Subscription",
              draft-boucadair-lisp-subscribe-03 (work in progress), July
              2016.

Authors' Addresses

   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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