[rbridge] Preview of changes for VLANs, etc.

[Anoop Ghanwani]

> -----Original Message-----
> From: rbridge-bounces at postel.org 
> [mailto:rbridge-bounces at postel.org] On Behalf Of Russ White
> Sent: Tuesday, November 06, 2007 12:15 PM
> To: Radia Perlman
> Cc: Developing a hybrid router/bridge.
> Subject: Re: [rbridge] Preview of changes for VLANs, etc.
> 
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> 
> > Certainly I'd love to get rid of the outer VLAN tag. Unfortunately, 
> > bridges on the link can be configured in weird ways such 
> that the only 
> > way to send a packet is using a particular set of VLAN tags. Then 
> > there are other complicated issues,
> 
> Since this is probably going to be 5% or less of the cases, 
> we should make this capability optional, and make the 95% 
> case the simpler case of sending with no vlan tag. The only 
> case this really arises in is when you have hosts on links 
> with through traffic, which any good network designer avoids 
> like the plague.
> 
> I'd rather not make this whole thing really complicated just 
> to support a small set of networks....

It's not that simple...again back to terminology:

- For ports that support only bridged traffic 802.1
  defines what they should do.
- For ports that support only TRILL traffic, we
  get to define how they operate (within some limits
  since we may still see link-local control traffic).
- For ports that support both bridged and TRILL
  traffic we have to go with what 802.1 says
  (otherwise the traffic won't go through bridges).

Thus far, all RBridge ports are assumed to be 
of the last type.  That means the encapsulation has
to follow rules defined by 802.1 - i.e. you have
a set of VLANs on that port.  We only transmit
traffic on those VLANs.  Some of those VLANs belong
to the "tagged set" in which case we transmit frames
for those VLANs in tagged format; other VLANs belong
to the "untagged" set in which case we transmit 
frames without a tag.

I think what we have defined so far is fine.
There is no need to change it.  Making it optional
won't work.

Even routers have to follow those rules or
their packets don't make it through the LAN!

Anoop