Subject: [trill] FGL tweak for improved migration

From: Donald Eastlake <[email-masked]>
Date: Wed, 23 Jan 2013 23:39:58 -0500

Hi,

As described in draft-ietf-trill-fine-labeling-04, a VL TRILL switch
cannot safely handle an FGL TRILL Data packet: it might egress such a
frame out an incorrect port in the wrong VLAN or re-order frames due
to incorrect ECMP flow classification or pre-maturely prune
distribution if the frame is multi-destination. The draft solves this
by blocking data communication between VL and FGL TRILL switches.
However, this makes migration from VL to FGL more difficult.

Since I believe that all, or almost all, existing VL RBridges can be
upgraded to Limited FGL by a software change, a small relaxation of
this blocking makes it possible to migrate more smoothly. The data
adjacency blocking can be relaxed so that VL and Limited FGL TRILL
switches are adjacent as long as there are no Full FGL TRILL switches
in the topology. This permits a smooth migration from VL to Limited
FGL by upgrading VL TRILL switches and adding Limited FGL TRILL
switches. After which Full FGL TRILL switches could be added, or
Limited FGL upgraded to Full. This safely maintains general data
connectivity.

Thanks,
Donald
=============================
 Donald E. Eastlake 3rd   +1-508-333-2270 (cell)
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