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Versions: 00 01 02

Network Working Group                                          C. Cassar
Internet-Draft                                               I. Kouvelas
Intended status: Experimental                                   J. Leong
Expires: March 26, 2015                                         D. Lewis
                                                              G. Schudel
                                                           Cisco Systems
                                                      September 22, 2014


                   LISP RLOC Membership Distribution
               draft-kouvelas-lisp-rloc-membership-00.txt

Abstract

   The Locator/ID Separation Protocol (LISP) operation is based on EID
   to RLOC mappings that are exchanged through a mapping system.  The
   mapping system can use the RLOCs included in mapping registrations to
   construct the complete set of RLOC addresses across all xTRs that are
   members of the LISP deployment.  This set can then be made available
   by the mapping system to all the member xTRs.  An xTR can use the
   RLOC set to optimise protocol operation as well as to implement new
   functionality.  This document describes the use of the LISP reliable
   transport session between an xTR and a Map-Server to communicate the
   contents of the RLOC membership set.

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 March 26, 2015.

Copyright Notice

   Copyright (c) 2014 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
   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.  Requirements Notation . . . . . . . . . . . . . . . . . . . .   3
   3.  Membership Distribution Overview  . . . . . . . . . . . . . .   4
   4.  Membership Message Format . . . . . . . . . . . . . . . . . .   4
     4.1.  Membership Subscribe  . . . . . . . . . . . . . . . . . .   5
     4.2.  Membership Subscribe ACK  . . . . . . . . . . . . . . . .   6
     4.3.  Membership Subscribe NACK . . . . . . . . . . . . . . . .   7
     4.4.  Membership Unsubscribe  . . . . . . . . . . . . . . . . .   8
     4.5.  Membership Element Add  . . . . . . . . . . . . . . . . .   9
     4.6.  Membership Element Delete . . . . . . . . . . . . . . . .  10
     4.7.  Membership Refresh Request  . . . . . . . . . . . . . . .  10
     4.8.  Membership Refresh Begin  . . . . . . . . . . . . . . . .  11
     4.9.  Membership Refresh End  . . . . . . . . . . . . . . . . .  12
   5.  Membership Distribution Message Exchange  . . . . . . . . . .  12
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  14
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  14
   8.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  14
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  15
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  15
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  15
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  15

1.  Introduction

   The Locator/ID Separation Protocol (LISP) registration process
   between an xTR and a Map-Server is defined in [RFC6833].  In each
   registration message the xTR communicates mapping records providing
   the list of routing locators (RLOCs) that can be used to reach the
   endpoint identifier (EID) space behind the xTR.  By gleaning the
   RLOCs from all such registrations, the map-server constructs the set
   of RLOCs across all the received registrations.  This set represents
   all the RLOCs used to encapsulate traffic and is the complete RLOC
   membership of the LISP network (limitations described below).

   The gleaned RLOC membership set is communicated to the member xTRs
   where it can be used to implement new functionality as well as to



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   optimise protocol operation.  As one example in deployments where the
   RLOC network provides guarantees against RLOC source address spoofing
   the membership can be used as a decapsulation filter to prevent
   injection of traffic by non-members.  As a second example, a possible
   optimisation to existing functionality can use changes to the RLOC
   membership set to validate the xTR map-cache contents and trigger
   updates for out-of-date mappings.

   Distribution of the RLOC membership set is practical in VPN use cases
   [I-D.lewis-lisp-vpns] where the number of member xTRs and their RLOCs
   is bounded thus limiting both the number of membership elements that
   must be distributed as well as the number of members that the set
   must be distributed to.  In a VPN use case the membership set is
   specific to each VPN identified through the LISP Instance ID (IID).
   It is reasonable to expect that all member xTRs for a specific VPN
   can register against a pair of redundant Map-Servers.  The complete
   membership set will therefore be available on those Map-Servers.
   Alternatively, registration can be across a small set of Map-Servers
   that synchronise the RLOC membership set between them (outside the
   scope of this document).  In the general case the RLOC membership
   knowledge is split across a distributed mapping system
   [I-D.ietf-lisp-ddt] and its collection and distribution would hit
   scale limits.

   Membership gleaning at the Map-Server assumes symmetric ITR and ETR
   deployments.  All encapsulating ITRs also have to be configured as
   ETRs registering against the Map-Servers.  This is a common way of
   deploying LISP xTRs.  To allow members that do not own EID space
   (such as exclusive ITRs and proxy routers) to be included in the
   membership set the registration mechanism must be extended.

   Note that automatic membership gleaning at the Map-Server through
   registrations is just one mechanism that can be used to discover the
   RLOC set to be distributed.  This document focuses on the membership
   set distribution mechanism.

   The LISP extension in [I-D.kouvelas-lisp-reliable-transport]
   introduces a reliable transport session between the xTR and the MS.
   The membership set communication described in this document is based
   on message exchange over the reliable transport.

2.  Requirements Notation

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].





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3.  Membership Distribution Overview

   The RLOC membership set distribution from the Map-Server to the xTR
   is initiated on demand by the xTR.  Unless the xTR specifically
   subscribes to receive the RLOC membership set no action is taken by
   the Map-Server.  The granularity at which a Map-Server gleans
   membership, and that an xTR can request its distribution, is per EID
   address family and instance ID.  This matches the VPN EID space
   segmentation model allowing separate communication of the membership
   of different VPNs.  It also allows for each EID address family to
   have a different xTR membership.

   The Map-Server SHOULD only allow the distribution of the RLOC
   membership set for an EID instance and address family to xTRs that
   are valid members of the set being distributed.  An xTR that has a
   reliable transport session established with the Map-Server and is
   registering EID prefixes with the Map-Server but not for the specific
   instance ID and EID address family, SHOULD NOT be sent the RLOC
   membership set.

   The set of member RLOCs for an EID address family and instance ID is
   dynamic and changes as new registrations are received by the Map-
   Server and as registration state times out.  When membership
   distribution is initiated by the xTR, the complete RLOC set contents
   is communicated.  In parallel updates to the membership set begin
   being communicated.  The membership set updates continue for the
   duration of the reliable transport session or until the xTR
   unsubscribes from the membership distribution.

4.  Membership Message Format

   The membership distribution exchange between the xTR and Map-Server
   over the reliable transport session relies on a number of new
   messages defined below.  The use of these messages is described in
   the following sections.  The table below lists the messages.  All
   messages carry the EID address family and instance ID for the
   membership distribution.  Some messages additionally carry extra
   fields that are listed in the table.  The new messages are:













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       +------+-----------------+-----------+---------------------+
       | Type | Message         | Direction | Additional fields   |
       +------+-----------------+-----------+---------------------+
       | 22   | Subscribe       | xTR -> MS |                     |
       |      |                 |           |                     |
       | 23   | Subscribe ACK   | MS -> xTR | Subscribe ID        |
       |      |                 |           |                     |
       | 24   | Subscribe NACK  | MS -> xTR | Subscribe ID, Error |
       |      |                 |           |                     |
       | 25   | Unsubscribe     | xTR -> MS |                     |
       |      |                 |           |                     |
       | 26   | Element Add     | MS -> xTR | Site-ID, RLOC       |
       |      |                 |           |                     |
       | 27   | Element Delete  | MS -> xTR | Site-ID, RLOC       |
       |      |                 |           |                     |
       | 28   | Refresh Request | xTR -> MS |                     |
       |      |                 |           |                     |
       | 29   | Refresh Begin   | MS -> xTR | Request ID          |
       |      |                 |           |                     |
       | 30   | Refresh End     | MS -> xTR | Request ID          |
       +------+-----------------+-----------+---------------------+

         Table 1: Reliable transport membership distribution TLVs

   The rest of this section provides the format of each of the messages
   in the table.  For a description of the Type, Length, Message ID and
   Message End Marker fields refer to
   [I-D.kouvelas-lisp-reliable-transport].

4.1.  Membership Subscribe

   The Membership subscribe message is sent by the xTR to the Map-Server
   to initiate RLOC membership set distribution for a specific EID AFI
   and instance ID.

















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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 = 22           |            Length             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                           Message ID                          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |            EID AFI            |            EID IID          ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ...                             |       Message End Marker    ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ...                             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                    Membership subscribe message format

   o  EID-AFI: EID address family for which the membership is being
      requested.

   o  EID IID: The EID instance ID identifying the VPN for which the
      membership is being requested [I-D.lewis-lisp-vpns].  Although the
      IID is only 24 bits in size in the data encapsulation, it is being
      defined as a 32 bit field for consistency with the LCAF Instance
      ID header [I-D.ietf-lisp-lcaf].

4.2.  Membership Subscribe ACK

   The Membership-Subscribe-ACK message is sent by the Map-Server to the
   xTR to acknowledge acceptance of a Membership-Request.  This message
   indicates that the Map-Server will be providing the requested
   membership to the xTR.




















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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 = 23           |            Length             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                           Message ID                          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |            EID AFI            |            EID IID          ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ...                             |      Subscribe message ID   ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ...                             |       Message End Marker    ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ...                             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                  Membership-Subscribe-ACK message format

   o  Subscribe message ID: The message ID carried over from the
      membership subscribe message.

4.3.  Membership Subscribe NACK

   The Membership-Subscribe-NACK message is sent by the Map-Server to
   the xTR to reject a membership request.  This message indicates that
   the Map-Server will not be providing the requested membership to the
   xTR.  The membership subscribe NACK message can be sent at any point
   following the receipt of a Membership-Subscribe message.  The Map-
   Server may initially acknowledge a subscription with a Membership
   Subscribe ACK and later when conditions change cancel the
   subscription by issuing a membership subscribe NACK message.




















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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 = 24           |            Length             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                           Message ID                          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |            EID AFI            |            EID IID          ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ...                             |      Subscribe message ID   ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ...                             |  Error code   |             ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ...           Message End Marker                |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                 Membership subscribe NACK message format

   o  Subscribe message ID: The message ID carried over from the
      membership subscribe message.

   o  Error code: The error code provides a reason for which the
      registration was rejected by the Map-Server.  Defined values are:

      1 -  Not found: The EID instance and address family do not match
           the Map-Server configuration.

      2 -  Not enabled: The Map-Server is not configured to allow
           membership distribution for the requested EID instance and
           address family.

      3 -  Not authorized: The xTR that sent the request does not have a
           valid registration under the EID instance and address family.

4.4.  Membership Unsubscribe

   The Membership-Unsubscribe message is sent by the xTR to the Map-
   Server to terminate RLOC membership set distribution for a specific
   EID AFI and instance ID.












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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 = 25           |            Length             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                           Message ID                          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |            EID AFI            |            EID IID          ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ...                             |       Message End Marker    ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ...                             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                   Membership-Unsubscribe message format

4.5.  Membership Element Add

   The Membership-Element-Add message is sent by the Map-Server to the
   xTR to communicate a single RLOC that is a member of the set for the
   specified EID instance and address family.

      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 = 26           |            Length             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                           Message ID                          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |            EID AFI            |            EID IID          ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ...                             |            Site ID          ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ...                     Site ID continued                     ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ...                             |        RLOC address AFI       |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                         RLOC address                        ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                       Message End Marker                      |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                   Membership-Element-Add message format

   o  Site ID: The 64 bit site ID value from the mapping registration
      that contributed this RLOC to the membership list.  The site ID
      can be used by the receiving xTR to derive information about the
      grouping of member RLOCs to remote sites.



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   o  RLOC address AFI: Address family identifier for the RLOC address
      in the following field.

   o  RLOC address: The actual RLOC membership set element address being
      communicated.  Note that the length of this field depends on the
      RLOC address AFI in the preceding field.

4.6.  Membership Element Delete

   The Membership-Element-Delete message is sent by the Map-Server to
   the xTR to communicate a single RLOC that is no longer a member of
   the set for the specified EID instance and address family.

      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 = 27           |            Length             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                           Message ID                          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |            EID AFI            |            EID IID          ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ...                             |            Site ID          ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ...                     Site ID continued                     ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ...                             |        RLOC address AFI       |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                         RLOC address                        ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                       Message End Marker                      |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                 Membership-Element-Delete message format

4.7.  Membership Refresh Request

   The Membership-Refresh-Request message is sent by the xTR to the Map-
   Server to request that the Map-Server send the complete RLOC
   membership set contents for the specified instance ID and AFI.











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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 = 28           |            Length             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                           Message ID                          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |            EID AFI            |            EID IID          ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ...                             |       Message End Marker    ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ...                             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                 Membership-Refresh-Request message format

4.8.  Membership Refresh Begin

   The Membership-Refresh-Begin message is sent by the Map-Server to the
   xTR to acknowledge an earlier Membership-Refresh-Request message and
   to indicate that the following membership updates are part of the
   refresh.

      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 = 29           |            Length             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                           Message ID                          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |            EID AFI            |            EID IID          ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ...                             |       Request message ID    ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ...                             |       Message End Marker    ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ...                             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                  Membership-Refresh-Begin message format

   o  Request message ID: The message ID carried over from the
      membership request message.








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4.9.  Membership Refresh End

   The Membership-Refresh-End message is sent by the Map-Server to the
   xTR to indicate that the communication of the full membership refresh
   for the specified EID instance ID and AF is now complete.

      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 = 30           |            Length             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                           Message ID                          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |            EID AFI            |            EID IID          ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ...                             |       Request message ID    ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ...                             |       Message End Marker    ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ...                             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                   Membership-Refresh-End message format

   o  Request message ID: The message ID carried over from the
      membership request message.

5.  Membership Distribution Message Exchange

   Following the reliable transport session establishment, the EID
   membership communication relies on the exchange of the membership
   messages defined in the previous section.  The description in this
   section presents the exchange from the perspective of a single xTR
   and Map-Server.

















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                       xTR                        MS
                       |                           |
                       | ------- Subscribe ------> |
                       |                           |
                       | <---- Subscribe ACK ----- |
                       |                           |
                       | ---- Refresh request ---> |
                       |                           |
                       | <---- Refresh begin ----- |
                       |                           |
                       | <----- Element add ------ |
                       | <----- Element add ------ |
                       | <----- Element add ------ |
                       |                           |
                       | <----- Refresh end ------ |
                       |                           |
                       | <-- Element add/delete -- |
                       |                           |
                       | ------ Unsubscribe -----> |

             Typical membership distribution message exchange

   The xTR starts the exchange by issuing a Membership-Subscribe-Request
   message to the Map-Server for a specific EID instance.  Assuming the
   Map-Server is configured to allow membership distribution and the
   requesting router is authorized to receive the membership of the EID
   instance, the MS will reply with a Membership-Subscribe-ACK.  After
   sending the ACK, the MS will start sending to the xTR Membership-
   Element-Add and Membership-Element-Delete messages corresponding to
   changes of the EID instance membership.

   On receipt of the Membership-Subscribe-ACK message, the xTR issues a
   Membership-Refresh-Request message in order to receive the complete
   contents of the EID instance membership held by the MS.  The MS
   responds to the Membership-Refresh-Request by issuing a Membership-
   Refresh-Begin message, followed by a Membership-Element-Add message
   for each member of the EID instance and finally completes the refresh
   by sending a Membership-Refresh-End message.

   On receipt of Membership-Element-Add and Membership-Element-Delete
   messages, the xTR updates its membership database for the EID
   instance ID and address family by adding or deleting the entry
   corresponding to the communicated RLOC address.  Note that the
   membership state on the xTR is Map-Server specific and the xTR has to
   maintain separate RLOC membership entries received from each Map-
   Server it subscribes with.





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   When the xTR receives the Membership-Refresh-End message it purges
   all the stale membership entries it may have obtained during a
   previous session instantiation that were not updated during the
   refresh.

   The MS may issue Membership-Element-Add and Membership-Element-Delete
   messages corresponding to membership changes at any point after
   issuing the Membership-ACK message, even during a refresh.

   The xTR may request additional full refreshes of the complete
   membership set at any point after having received a Membership-
   Subscribe-ACK message by issuing a new Membership-Refresh-Request.

   When the Map-Server determines that an xTR is no longer eligible to
   receive membership updates, for example the EID instance and address
   family registration state of the xTR becomes invalid, then the Map-
   Server SHOULD send it a Membership-NACK message to indicate the
   termination of the membership communication.

6.  Security Considerations

   The RLOC membership distribution message communication takes place
   over a LISP reliable transport connection.  The security mechanisms
   of the reliable transport apply to this solution.

7.  IANA Considerations

   The following message types must be assigned out of the space defined
   in [I-D.kouvelas-lisp-reliable-transport].

           Type   Name                           Reference
           -----  -----------------------------  --------------
           22     Membership Subscribe           This document
           23     Membership Subscribe ACK       This document
           24     Membership Subscribe NACK      This document
           25     Membership Unsubscribe         This document
           26     Membership Element Add         This document
           27     Membership Element Delete      This document
           28     Membership Refresh Request     This document
           29     Membership Refresh Begin       This document
           30     Membership Refresh End         This document

8.  Acknowledgments

   The authors would like to thank Michiel Blokzijl, Selina Heimlich,
   Vasileios Lakafosis, Fabio Maino, Andre Pelletier, Jesper Skriver and
   Chao Yu, for their contributions to this specification.




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9.  References

9.1.  Normative References

   [I-D.kouvelas-lisp-reliable-transport]
              Cassar, C., Kouvelas, I., and D. Lewis, "LISP Reliable
              Transport", draft-kouvelas-lisp-reliable-transport-01
              (work in progress), August 2014.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC6830]  Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The
              Locator/ID Separation Protocol (LISP)", RFC 6830, January
              2013.

   [RFC6833]  Fuller, V. and D. Farinacci, "Locator/ID Separation
              Protocol (LISP) Map-Server Interface", RFC 6833, January
              2013.

9.2.  Informative References

   [I-D.ietf-lisp-ddt]
              Fuller, V., Lewis, D., Ermagan, V., and A. Jain, "LISP
              Delegated Database Tree", draft-ietf-lisp-ddt-01 (work in
              progress), March 2013.

   [I-D.ietf-lisp-lcaf]
              Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical
              Address Format (LCAF)", draft-ietf-lisp-lcaf-05 (work in
              progress), May 2014.

   [I-D.lewis-lisp-vpns]
              Lewis, D. and G. Schudel, "LISP Virtual Private Networks
              (VPNs)", draft-lewis-lisp-vpns-00 (work in progress),
              February 2014.

Authors' Addresses

   Chris Cassar
   Cisco Systems
   10 New Square Park
   Bedfont Lakes, FELTHAM  TW14 8HA
   UNITED KINGDOM

   Email: ccassar@cisco.com





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   Isidor Kouvelas
   Cisco Systems
   Monumental Plaza, Building C
   44 Kifissias Ave.
   Maroussi, Athens  15125
   Greece

   Email: kouvelas@cisco.com


   Johnson Leong
   Cisco Systems
   Tasman Drive
   San Jose, CA  95134
   USA

   Email: joleong@cisco.com


   Darrel Lewis
   Cisco Systems
   Tasman Drive
   San Jose, CA  95134
   USA

   Email: darlewis@cisco.com


   Gregg Schudel
   Cisco Systems
   Tasman Drive
   San Jose, CA  95134
   USA

   Email: gschudel@cisco.com
















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