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Flexible Multilevel TRILL (Transparent Interconnection of Lots of Links)
draft-perlman-trill-rbridge-multilevel-08

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Last updated: 2014-06-30
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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: December 29, 2014                                 June 30, 2014

                       Flexible Multilevel TRILL
             (Transparent Interconnection of Lots of Links)
            <draft-perlman-trill-rbridge-multilevel-08.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 TRILL switch nicknames. There
   have been two proposed approaches.  One approach, which we refer to
   as the "unique nickname" approach, gives unique nicknames to all the
   TRILL switches in the multilevel campus, either by having the
   level-1/level-2 border TRILL switches 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 TRILL switches 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 <trill@ietf.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..............12
      2.2.2.2 Swap Nickname Field Aggregated Nicknames..........14
      2.2.2.3 Comparison........................................14
      2.3 Building Multi-Area Trees.............................15
      2.4 The RPF Check for Trees...............................15
      2.5 Area Nickname Acquisition.............................15
      2.6 Link State Representation of Areas....................16

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