Shim6: Level 3 Multihoming Shim Protocol for IPv6
RFC 5533

Network Working Group                                        E. Nordmark
Request for Comments: 5533                              Sun Microsystems
Category: Standards Track                                     M. Bagnulo
                                                                    UC3M
                                                               June 2009

           Shim6: Level 3 Multihoming Shim Protocol for IPv6

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (c) 2009 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 in effect on the date of
   publication of this document (http://trustee.ietf.org/license-info).
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.

Abstract

   This document defines the Shim6 protocol, a layer 3 shim for
   providing locator agility below the transport protocols, so that
   multihoming can be provided for IPv6 with failover and load-sharing
   properties, without assuming that a multihomed site will have a
   provider-independent IPv6 address prefix announced in the global IPv6
   routing table.  The hosts in a site that has multiple provider-
   allocated IPv6 address prefixes will use the Shim6 protocol specified
   in this document to set up state with peer hosts so that the state
   can later be used to failover to a different locator pair, should the
   original one stop working.

Nordmark & Bagnulo          Standards Track                     [Page 1]
RFC 5533                     Shim6 Protocol                    June 2009

Table of Contents

   1. Introduction ....................................................4
      1.1. Goals ......................................................5
      1.2. Non-Goals ..................................................5
      1.3. Locators as Upper-Layer Identifiers (ULID) .................6
      1.4. IP Multicast ...............................................7
      1.5. Renumbering Implications ...................................8
      1.6. Placement of the Shim ......................................9
      1.7. Traffic Engineering .......................................11
   2. Terminology ....................................................12
      2.1. Definitions ...............................................12
      2.2. Notational Conventions ....................................15
      2.3. Conceptual ................................................15
   3. Assumptions ....................................................15
   4. Protocol Overview ..............................................17
      4.1. Context Tags ..............................................19
      4.2. Context Forking ...........................................19
      4.3. API Extensions ............................................20
      4.4. Securing Shim6 ............................................20
      4.5. Overview of Shim Control Messages .........................21
      4.6. Extension Header Order ....................................22
   5. Message Formats ................................................23
      5.1. Common Shim6 Message Format ...............................23
      5.2. Shim6 Payload Extension Header Format .....................24
      5.3. Common Shim6 Control Header ...............................25
      5.4. I1 Message Format .........................................26
      5.5. R1 Message Format .........................................28
      5.6. I2 Message Format .........................................29
      5.7. R2 Message Format .........................................31
      5.8. R1bis Message Format ......................................33
      5.9. I2bis Message Format ......................................34
      5.10. Update Request Message Format ............................37
      5.11. Update Acknowledgement Message Format ....................38
      5.12. Keepalive Message Format .................................40
      5.13. Probe Message Format .....................................40
      5.14. Error Message Format .....................................40
      5.15. Option Formats ...........................................42
           5.15.1. Responder Validator Option Format .................44
           5.15.2. Locator List Option Format ........................44