Subject: [rbridge] Ingress Rbridge address and BCN

From: Eric.Gray at marconi.com (Gray, Eric)
Date: Fri, 27 Oct 2006 11:37:52 -0400

Silvano,

	Your assumption about retention of "inner MAC addresses" in
RBridges at the core network would be an implementation choice.
There is, and will be, no statement that "core RBridges MUST NOT 
retain advertisement information relating to MAC DA reachability.
Nor is it the case that this information is not made available to
RBridges in the core network.

	Hence, if an RBridge implementation has not retained MAC DA
reachability adsvertisements it receives, that is the choice made
by that RBridge's implementers.

	It is quite reasonable to assume that so-called core RBridges
may elect not to retain MAC reachability information in cases where
the "core RBridge" does not need this information.  Supposing that
a "core RBridge" may need this MAC reachability information and yet 
not have retained it, is arguably a "dumb implementation" issue, as
opposed to a protocol problem.

	Note that an RBridge needs only to have one interface on which
it has "delivery responsibility" (i.e. - is the designated RBridge)
for a "native LAN" device (such as an 802.1X bridge), and it cannot 
be a "core RBridge."  With this qualification of what it means to be
an RBridge in "core networks", this seems likely to be an exception
case, and it is well known that it is not a good idea to design any
protocol to be optimized for the exception case.

	Already, we have discussed the fact that BCN capable devices 
are typically segregated onto "BCN capable VLANs."  That being the 
case, it is certainly possible for an implementer to retain MAC DA
reachability advertisements for configured "BCN capable VLANS."

--
Eric

--> -----Original Message-----
--> From: rbridge-bounces at postel.org 
--> [mailto:rbridge-bounces at postel.org] On Behalf Of Silvano Gai
--> Sent: Friday, October 27, 2006 11:00 AM
--> To: Radia.Perlman at sun.com; Wadekar, Manoj K
--> Cc: rbridge at postel.org
--> Subject: Re: [rbridge] Ingress Rbridge address and BCN
--> 
--> 
--> If the congestion is detected in the core of the TRILL 
--> network, how do
--> you signal back to the source host if you don't know which is the
--> ingresss RBridge? 
--> 
--> You cannot look-up the inner MAC address, because in the core of the
--> network you don't keep the inner MAC addresses in the 
--> table. Correct?
--> 
--> This is a clear reason while you need the ingress RBridge address.
--> 
--> -- Silvano
--> 
--> > -----Original Message-----
--> > From: rbridge-bounces at postel.org 
--> [mailto:rbridge-bounces at postel.org]
--> On
--> > Behalf Of Radia.Perlman at sun.com
--> > Sent: Thursday, October 26, 2006 5:02 PM
--> > To: Wadekar, Manoj K
--> > Cc: rbridge at postel.org
--> > Subject: Re: [rbridge] Ingress Rbridge address and BCN
--> > 
--> > Hi Manoj,
--> > 
--> > I'm confused about BCN. Wouldn't congestion notification 
--> need to go to
--> the
--> > original endnode source,
--> > and not the ingress RBridge?
--> > 
--> > Radia
--> > 
--> 
--> 
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