Subject: [rbridge] dist tree parallel links - asymetric

From: jeff pickering <[email-masked]>
Date: Mon, 22 Jun 2009 08:55:24 -0700

I have a distribution tree parallel links question I was hoping someone 
could clarify
for me.

Let's say you have 2 RBs downstream from the root, with parallel links 
between them.

RB-A has cost 10 on link 1, cost 20 on link 2.
RB-B has cost 20 on link 1, cost 10 on link 2.

Lets say RB-B is downstream from RB-A. When computing its paths, RB-A 
will clearly
use link 1. Whether it shows 1 or 2 links in its LSPs is irrelevant, 
RB-B still needs to know
somehow to choose its adjacency over link 1 for its path to the root. 
But in the asymetric cost
case, I dont see how its can do this. Is there something new in either 
the LSP or hello that
would resolve this?

Or should RB-B use its lower cost and if so how does the RPF issue get 
addressed?

Thanks to anyone who can enlighten me.

Jeff

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From: Ayan Banerjee <[email-masked]>
Date: Mon, 22 Jun 2009 10:05:27 -0700

Jeff,

In TRILL 3-way handshake is mandatory for P2P links. Hence, each node will
get an unique extended circuit identifier after adjacency formation. On LAN
links, the source mac can be used an identifier for uniqueness of each link.

I believe that P2P links are preferred over LAN links. Among the set, in the
event there are multiple "identifiers" then the highest (or lowest - I
remember that there was some discussion on the list about highest/lowest, do
not recall what we ended up with) one will be chosen for the tree.

Thanks,
Ayan