Subject: [rbridge] TRILL Adjacency Event A7

From: Perry Gagne <[email-masked]>
Date: Tue, 27 Mar 2012 14:39:59 -0400

Hello,

I have a question regarding the one of the adjacency events describe in 
RFC 6327.

http://tools.ietf.org/html/rfc6327#section-3.3

Event A7 is describe as "MTU test was successful but now fails", how 
could this happen?

Is there a case where this can happen? The only one I can come up with 
is if  RB1 successfully tests RB2, then RB2 unsuccessfully tests RB1. 
The base RFC says you just need to test the MTU when an adjacency comes 
up. This event seems to indicate one would test the MTU every X period 
of time.

I am trying to design a conformance test around this (part of a larger 
set of tests related to RFC 6327) so I am trying to find the best way to 
simulate this.

Thank You
-- 
Perry R. Gagne
Research and Development
Bridge Functions Consortium

InterOperability Lab, University of New Hampshire
Email: [email-masked]
Phone (BFC): +1-603-862-3525
_______________________________________________
rbridge mailing list
[email-masked]
http://mailman.postel.org/mailman/listinfo/rbridge

---

From: Mingui Zhang <[email-masked]>
Date: Tue, 27 Mar 2012 20:01:26 +0000

Hi Perry,

Please see comments inline below.

Best regards,
Mingui
________________________________________
发件人: [email-masked] [[email-masked]] 代表 Perry Gagne [[email-masked]]
发送时间: 2012年3月28日 2:39
到: [email-masked]
主题: [rbridge] TRILL Adjacency Event A7

Hello,

Is there a case where this can happen?

[ZMG] I recommend you read draft-zhang-trill-mtu-negotiation-02. Both Figure 2.1 and Figure 2.2 are such examples. 

The only one I can come up with
is if  RB1 successfully tests RB2, then RB2 unsuccessfully tests RB1.
The base RFC says you just need to test the MTU when an adjacency comes
up. This event seems to indicate one would test the MTU every X period
of time.

[ZMG] Since MTU testing can be resource consuming. Periodically MTU testing should not be encouraged. Since the link MTU testing depends on the campus-wide Sz, RBridges should trigger MTU testing each time the campus-wide Sz changes. 

Thank You

---

From: Radia Perlman <[email-masked]>
Date: Tue, 27 Mar 2012 13:47:59 -0700

How could that happen?  Perhaps the link between R1 and R2 is a
bridged link, and the topology changes, and now the (spanning tree)
path between R1 and R2 goes through different bridges with different
MTUs than the first path.

Radia