Subject: [rbridge] Ingress Rbridge address and BCN - 2nd Issue

From: kreeger at cisco.com (Larry Kreeger (kreeger))
Date: Fri, 27 Oct 2006 15:06:14 -0700

Caitlin Bestler wrote on Friday, October 27, 2006 2:55 PM:

> Larry Kreeger, responding to Eric Gray, wrote:
>>> 
>>> 1) Flooding will only occur when a specific RBridge has removed (due
>>> to aging, for example), or failed to retain, an entry it
>>> subsequently needs. This kind of flooding could occur in any case
>>> (although it might involve a smaller subset of the entire network).
>> 
>> I understand that this will occur when an edge RBridge does not have
>> an entry, but I assume that this will be a fairly rare condition.
>> Also, I am expecting the number of flows through an edge RBridge to
>> be much less than throught a core RBridge, such that the number of
>> MAC addresses entries needed would be much less at an edge RBridge. 
>> If a core RBridge did not have a larger table, then it could get
>> easily filled which would require flooding of the BCNs much more
>> than would occur naturally at an edge RBridge.
>> 
> More fundamentally, the egress rbridge will in most case also
> encapsulate the reverse-bound frames, and so will have had a reason
> to note the mac->rbridge mapping in the first place. A "core rbridge"
> would not have forgotten the mapping, it would have never looked for
> it in the first place. Table size is irrelevant.   

Caitlin,

I agree with you (I think).  Core RBridges should not need to populate a
MAC table just in case they need to generate a BCN.  Given that, we have
two choices.  Either flood the BCN (which I don't like at all), or add
the source RBridge so it can be simply copied to the destination RBridge
of the BCN (which I do like).

 - Larry