[rbridge] Preview of changes for VLANs, etc.

[Anoop Ghanwani]

Hi Radia,

I think the proposal is reasonable in that per-VLAN
hellos are now optional (and can be made use of in
certain scenarios).  However, what is not specified
is the recipient behavior.  Can an RBridge choose
to ignore hellos from all other VLANs except the
one it is configured to send hellos on?  It seems
like that should be allowed because it won't do 
anything other than detect misconfigurations that
can also be detected by other means (although 
perhaps taking slightly longer to be detected).

If that recipient behavior is not allowed, we will
still get into scaling issues with having to receive
and process hellos from potentially all VLANs 
configured on a port.

Anoop 

> -----Original Message-----
> From: rbridge-bounces at postel.org 
> [mailto:rbridge-bounces at postel.org] On Behalf Of Radia Perlman
> Sent: Monday, November 05, 2007 2:52 PM
> To: Developing a hybrid router/bridge.
> Subject: [rbridge] Preview of changes for VLANs, etc.
> 
> Based on talking to people, here is how I'm assuming the VLAN 
> stuff will look. The main points are
> 
> a) single DRB per link (rather than DRB election per VLAN).
> 
> b) that DRB can delegate to another RBridge on the link the 
> job of forwarding VLAN-x data to/from the link.
> 
> c) RBridges MAY be configured to send Hellos on a set of 
> VLANs, though VLAN 1 is the default. They are also configured 
> with a single preferred VLAN "V". If RBridge RB1 is DRB, it 
> tells all the other RBridges on the link to send ALL 
> RBridge-Rbridge traffic (Hellos, LSPs, forwarded encapsulated 
> data traffic) with outer VLAN tag "V".
> 
> d) For safety, the DRB RB1 continues to send Hellos not only 
> on V, but on all the VLANs that RB1 is configured to send Hellos on.
> 
> e) The set of VLANs that RB1 is configured to support on the 
> link may be greater than the set of VLANs that RB1 is 
> configured to send Hellos on
> 
> f) We use all the link-avoidance stuff we'd discussed before 
> (don't decapsulate from ingress RBx unless you have RBx's LSP 
> and all pseudonodes that RBx claims to be attached to, and 
> can verify that none of them have the same root bridge ID as 
> the link you are about to decapsulate onto -- also, be 
> conservative about when you start encapsulting data off the 
> link by waiting a few Hello intervals, and waiting until 
> you've synchornized LSP databases with your neighbors).
> 
> g) IS-IS Hellos list the set of neighbors from which Hellos are heard.
> Once the DRB RB1 specifies "V" as the VLAN, the only 
> neighbors listed in IS-IS Hellos are those from which a Hello 
> is received on VLAN V.
> 
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