Technical Summary
Extending TRILL to multiple levels has challenges that are not
addressed by the already-existing capability of IS-IS to have
multiple levels. One issue is with the handling of multi-destination
packet distribution trees. Another 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 hiding the nicknames within
areas, 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.
This informational document suggests allowing a choice of approach in
each area. This allows the simplicity of the unique nickname approach
in installations in which there is no danger of running out of
nicknames and allows the complexity of hiding the nicknames in an
area to be phased into larger installations on a per-area basis.
Working Group Summary
WG has worked on these solutions for 2+ years.
The WG consensus had no objections, and support of all key players with comments.
WG LC:
https://www.ietf.org/mail-archive/web/trill/current/msg07079.html
Document Quality
Protocol extension has no implementation of this code.
Huawei plans to implement this function.
Personnel
Document shepherd: Susan Hares
Responsible AD: Alia Atlas