[rbridge] Ingress Rbridge address and BCN - 1st Issue
Larry Kreeger (kreeger)
kreeger at cisco.com
Fri Oct 27 16:38:58 PDT 2006
Gray, Eric wrote on Friday, October 27, 2006 3:20 PM:
> A slower look up may be okay for exception processing.
It depends on how much slower. Low latency of BCN is very important to
the stability of the feedback loop.
> BCNs should be required far less often than frames are being
> Having a transit RBridge "look inside [at?] the inner MAC"
> is not what is effectively happening - as I understand it - when a
> "core RBridge" is generating a BCN. BCN-capable core RBridges would
> presumably copy the header information from some subset of the frames
> on a minimally-congested link, strip the tunneling encapsulation and
> originate a new frame containing a Notification (BCN) message.
> This must be a new frame, as opposed to a reflection of the
> frame, so it is interesting that people assume this is a trivial
> operation in hardware in the first place.
> Since the BCN-capable RBridge has to "flip" the MAC SA into a
> in a BCN anyway, it MUST look at that part of the frame in every case
> before it can generate a BCN.
You are right, the RBridge would have to parse to inner SA to build the
> In effect, the frame is (partially) copied, the copied
> is locally terminated and used to originate a new message. This
> message would then be sent - presumably using the usual means for
> message origination - by encapsulating it in RBridge tunnel
> encapsulation and forwarding it to (at least) the ingress RBridge
> from which it was introduced.
> That is not nearly as much of a confusion of layers as it is to
> assume that the frame is munged in hardware and turned around
Yep, it isn't a munged frame, it is a brand new frame built using info
from the sampled frame.
> and 2) normal processing of originated local messages is bypassed in
> attempt to optimize BCN sending at the cost of including additional
> information in _every_ frame.
Here I disagree. Since the BCN is a new frame built using info from the
sampled frame, I see no problem in building the shim based on the info
in the sampled shim.
> Oh, and, apparently I can blame you for trying... :-)
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