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Flexible Multilevel TRILL (Transparent Interconnection of Lots of Links)

Document type: Expired Internet-Draft (individual)
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Last updated: 2015-01-01 (latest revision 2014-06-30)
Intended RFC status: Unknown
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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.


Radia Perlman <>
Donald Eastlake <>
Anoop Ghanwani <>
Hongjun Zhai <>

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid)