[rbridge] RBridge: a case of study

[James Carlson]

Eastlake III Donald-LDE008 writes:
> From: James Carlson [mailto:james.d.carlson at sun.com] 
[...]
> Eric Gray writes:
[...]
> > 2) all frames forwarded from a (physical) port on one RBridge 
> >    to a (physical) port on another RBridge MUST have the same
> >    VID, or 
[...]
> @@@ Well, I am Donald and I meant something like (2) but a bit narrower.
> I would have said "all TRILL frames" because "all frames" is way too
> inclusive. What about control frames like 802.1AB? Furthermore, in the
> case of point-to-point links between two Rbridges (i.e., no bridges or
> end station connections in between), as far as I can see there is no
> particular utility in considering the TRILL frames to have any external
> VLAN coloring and certainly no need for them to be outer tagged with a
> VLAN ID or priority.

I mostly agree with that.  In fact, I think that's a desirable end
state for TRILL, when all other bridges are obsolete.  Having no VLAN
tag on the outside makes a lot of sense there.

(I think omitting the priority makes a bit less sense to me, though.
Wouldn't you want the priority value set on an 802.1q header with VLAN
ID 0 in this case?)

I think the question is how to get there when there are networks that
are half-TRILL and half-otherwise.

> @@@ Well, your version of (3) above is, as I recall, roughly how things
> were in draft -04.

Yes.

> However, by -05 posted in July of this year (except
> in the pseudo code which is clearly labeled as still being that from
> -04), in order to actually provide the promised optimal pair-wise
> routing, the Outer and Inner VLANs are completely decoupled. See, for
> example, Section 4.1.2 of -05. And some recent proposals suggest using a
> single Outer VLAN ID on a link. 

As long as these things are manually configured, as described in
4.1.2, I don't see a problem.

As I understood Silvano Gai's discussion, it seemed he didn't want to
have those things be manually configured, so the RBridges would
somehow "find" each other on whatever underlying outer VLAN IDs might
be available and then forward packets without regard to the
restrictions placed on those other VLANs.

Perhaps I've misunderstood *that* part of it, but it's that part that
I wanted to clarify.

> The distinction with (2) in your list is that (2) appears to rule out
> the use of so-called "tagged" or leaf or ingress ports, forcing all
> ports to carry VLAN tags.
> 
> @@@ I find your above statement a bit confusing. Item (2) seems to be
> talking about TRILL frames between Rbridges which doesn't have anything
> to do with ingressing native frames.

The original statement said this:

  2) all frames forwarded from a (physical) port on one RBridge 
     to a (physical) port on another RBridge MUST have the same
     VID [...]

Packets that don't have VLAN tags (such as those on "tagged" ports)
don't have ID numbers.

-- 
James Carlson, Solaris Networking              <james.d.carlson at sun.com>
Sun Microsystems / 35 Network Drive        71.232W   Vox +1 781 442 2084
MS UBUR02-212 / Burlington MA 01803-2757   42.496N   Fax +1 781 442 1677