Subject: Re: [rbridge] Is Inner VLAN Tag Required?

From: Anil Rijhsinghani <[email-masked]>
Date: Mon, 13 Sep 2010 14:44:43 -0400

Donald,

> On the other hand, if you could determine the VLAN of the encapsulated
> frame from MAC addresses or Ethertype or the like and you knew that
> all the RBridges in the campus could do that, maybe you could
> configure something outside the existing TRILL standard to omit the
> Inner.VLAN. And it would be nice to save those bytes. But you still
> have the question of priority. TRILL is designed so as not to be
> dependent on the presence of the Outer.VLAN so I don't think you can
> depend on that for priority.

The flip side of this is that without an outer VLAN header, the
inner VLAN header isn't seen by 802.1-bridged islands (it's payload) so
TRILL data frames don't get prioritized the way they want.

With the draft queued for publication, I realize this is just an interesting
rehash of past discussions.

Thanks,
Anil

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From: Donald Eastlake <[email-masked]>
Date: Mon, 13 Sep 2010 18:48:54 -0400

Hi Anil,

> TRILL data frames don't get prioritized the way they want.

Yes. Sometimes the Outer.VLAN priority and/or VLAN could be essential
to getting the service you want or just getting through a bridged LAN
between RBridges. On the other hand, if you have all point-to-point
physical links between RBridges, say in a data center, then the
Outer.VLAN can always be omitted.

Thanks,
Donald