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Flexible Multilevel TRILL (Transparent Interconnection of Lots of Links)
draft-perlman-trill-rbridge-multilevel-07

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Last updated: 2014-01-02
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TRILL Working Group                                        Radia Perlman
INTERNET-DRAFT                                                Intel Labs
Intended status: Informational                           Donald Eastlake
                                                                  Huawei
                                                          Anoop Ghanwani
                                                                    Dell
                                                            Hongjun Zhai
                                                                     ZTE
Expires: July 1, 2014                                    January 2, 2014

                       Flexible Multilevel TRILL
             (Transparent Interconnection of Lots of Links)
            <draft-perlman-trill-rbridge-multilevel-07.txt>

Abstract

   Extending TRILL to multiple levels has one challenge that is not
   addressed by the already-existing capability of IS-IS to have
   multiple levels. The issue is with RBridge nicknames. There have been
   two proposed approaches.  One approach, which we refer to as the
   "unique nickname" approach, gives unique nicknames to all the
   RBridges in the multilevel campus, either by having the
   level-1/level-2 border RBridges advertise which nicknames are not
   available for assignment in the area, or by partitioning the 16-bit
   nickname into an "area" field and a "nickname inside the area" field.
   The other approach, which we refer to as the "aggregated nickname"
   approach, involves assigning nicknames to the areas, and allowing
   nicknames to be reused in different areas, by having the border
   RBridges rewrite the nickname fields when entering or leaving an
   area. Each of those approaches has advantages and disadvantages. The
   design in this document allows a choice of approach in each area,
   allowing the simplicity of the unique nickname approach in
   installations in which there is no danger of running out of
   nicknames, and allowing nickname rewriting to be phased into larger
   installations on a per-area basis.

Status of This Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.  Distribution of this document is
   unlimited.  Comments should be sent to the TRILL working group
   mailing list <rbridge@postel.org>.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

R. Perlman, et al                                               [Page 1]
INTERNET-DRAFT                                          Multilevel TRILL

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Acknowledgements

   The helpful comments of the following are hereby acknowledged: David
   Michael Bond and Dino Farinacci.

R. Perlman, et al                                               [Page 2]
INTERNET-DRAFT                                          Multilevel TRILL

Table of Contents

      1. Introduction............................................4
      1.1 TRILL Scalability Issues...............................4
      1.2 Improvements Due to Multilevel.........................5
      1.3 Unique and Aggregated Nickanmes........................6
      1.3 More on Areas..........................................6
      1.4 Terminology and Acronyms...............................7

      2. Multilevel TRILL Issues.................................8
      2.1 Non-zero Area Addresses................................9
      2.2 Aggregated versus Unique Nicknames.....................9
      2.2.1 More Details on Unique Nicknames....................10
      2.2.2 More Details on Aggregated Nicknames................11
      2.2.2.1 Border Learning Aggregated Nicknames..............11
      2.2.2.2 Swap Nickname Field Aggregated Nicknames..........13
      2.2.2.3 Comparison........................................14
      2.3 Building Multi-Area Trees.............................14
      2.4 The RPF Check for Trees...............................15
      2.5 Area Nickname Acquisition.............................15
      2.6 Link State Representation of Areas....................16

      3. Area Partition.........................................17

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