[rbridge] Preview of changes for VLANs, etc.

[Anoop Ghanwani]

> -----Original Message-----
> From: Russ White [mailto:riw at cisco.com] 
> Sent: Wednesday, November 07, 2007 4:44 AM
> To: Anoop Ghanwani
> Cc: Radia Perlman; Developing a hybrid router/bridge.
> Subject: Re: [rbridge] Preview of changes for VLANs, etc.
> 
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> 
> >>> 1. Find the next hop, by looking at the tree.
> >>> 2. Figure out the outbound interface.
> >>> 3. Encap the packet with the correct layer 2 header for that 
> >>> interface.
> >>> 3a. If the outbound interface is a subinterface, the 
> layer 2 header 
> >>> will include, of course, a vlan header.
> >>> 3b. If the outbound interface is not a subinterface, the layer 2 
> >>> header will not include a vlan header.
> 
> >> I agree with this.
> 
> Since this is obviously not the forwarding path for rbridges, 
> I think it would be very useful if you could outline the 
> actual forwarding path, with all the possible "if" statements 
> involved.

I thought that is what the draft does.

> If an rbridge receives a unicast packet without a VLAN tag, it will:

Assuming we're talking about the inner tag...

The problem with special casing the no-VLAN case
is that we're now build a new type of bridging 
that combines 802.1D with 802.1Q, and in the 
process will likely break both.  With 802.1Q
a packet always has a VLAN context.  With 802.D
there is no VLAN context.  This matters especially
when you encounter situations with the same
MAC addresses in different VLANs.
 
Anoop