[rbridge] How are packets/link without a VLAN tag handled in a bridged network today?

[Radia Perlman]

I guessed at the behavior once, to someone who was following 802.1 
better than I have
been, and he verified that I was correct at the time, but I've forgotten 
what my
conjecture was. Does anyone know how the following cases are handled?

Suppose a bridged network has some links configured
as VLAN A, and others configured as VLAN B, and some links that are not 
configured
as either VLAN A or VLAN B. Let's say that links La1 and La2 are configured
as VLAN A, links Lb1 and Lb2 are configured as Lb, and links Lc1 and Lc2 
are not configured
to reside in either VLAN A or VLAN B.

Let's further assume that it is the bridges that put on the VLAN tags.

What happens in the following cases?

a) A layer 2 multicast packet originates at La1. Certainly the first bridge
adds a VLAN A tag to the packet, and delivers the packet to La2. However,
does it also deliver it to Lc1 and Lc2? (I'd be very surprised if the 
answer to this
was yes...I assume the packet will ONLY get delivered to links that are
specifically marked as supporting VLAN A).

b) A layer 2 multicast packet originates at Lc1. I assume the behavior 
in this case
is that the first bridge does NOT add a VLAN tag to the packet. I can 
imagine either
in this case that the packet is ONLY delivered to Lc2 (i.e., other links 
that are not
configured as belonging to any VLAN), but I suspect the packet is 
delivered to
ALL links, i.e., in this case, La1, La2, Lb1, Lb2, and Lc2, and without 
a VLAN tag.
This would mean that endnodes in VLAN A and endnodes in VLAN B will see 
this packet, so
perhaps it's the other behavior (that it's only delivered to links that 
are not configured as being
in any VLAN).

c) If it is the bridge, rather than endnodes that put on the VLAN tag, 
is it legal for a link
to support multiple VLANs? It would make sense for the answer to this to 
be no, in which
case I suspect the answer to b) above would be more likely to be "don't 
deliver to any links
that have been configured to be in any VLAN", since I suspect "unmarked 
VLAN" is treated as a special
case VLAN.

Radia