Subject: [trill] Multidestination frames over parallel P2P links

From: Petr Hroudný <[email-masked]>
Date: Wed, 28 Oct 2015 22:13:36 +0100

Hi all,

I'm looking for the WG opinion about forwarding of multidestination frames
over parallel P2P links between TRILL switches.

According to RFC6325, section 4.5.2, item 3 a), when multiple parallel P2P
links exist between RB1 and RB2:

"Most preferred are those established by P2P Hellos.Tiebreaking among those
is based on preferring the one with the numerically highest Extended
Circuit ID as associated with the adjacency by the RBridge with the highest
System ID."

Does it mean that link cost should be completely ignored during the above
tiebreaking?

Suppose the following setup:

link #1    cost: 1000      Extended Circuit ID: 11
link #2    cost: 1000      Extended Circuit ID: 12
link #3    cost: 10000    Extended Circuit ID: 13
link #4    cost: 2^24-1   Extended Circuit ID: 14

Should the switch really prefer link #4 because of the highest Extended
Circuit ID, regardless of the fact that the link cost was set to maximum in
order to take the link out of service?

    Thanks, Petr