[rbridge] Ambition with different VLAN configurations

[Anoop Ghanwani]

> -----Original Message-----
> From: rbridge-bounces at postel.org 
> [mailto:rbridge-bounces at postel.org] On Behalf Of Radia Perlman
> Sent: Monday, September 17, 2007 8:24 PM
> To: Developing a hybrid router/bridge.
> Subject: Re: [rbridge] Ambition with different VLAN configurations
> 
> So, just to summarize what I think the proposed solution is, 
> plus a couple of questions interspersed, marked with ???
> 
> a) on each layer 2 cloud, all RBrdge-RBridge communication 
> (including IS-IS Hellos and encapsulated data packet 
> forwarding) will be sent with one VLAN tag.
> 
> ???question: Which VLAN tag?  untagged? VLAN 1? Something 
> else? And is that the
> *only* VLAN tag, or is it a default, and RBridges could be 
> configured to send on a different VLAN tag? (I'd prefer 
> picking one and not have it be configurable)???
> 
> b) it will be a MUST to listen to spanning tree messages and 
> include the root bridge ID in the pseudonode LSP. Also,

And the root bridge ID in the case where MSTP is enabled
is that of the CIST.

It must also include in the list of VLANs reachable on
that pseudonode and what is configured as the "RBridge 
control VLAN".  The list of VLANs reachable is later 
used for doing DRB election.

> c) if R1 notices a pseudonode with a root bridge that is the 
> same as a link that R1 thinks
> R1 is designated on, R1 does not forward data to/from that 
> link if R1's 6-byte IS-IS ID is less than the ID of  the DRB 
> for that pseudonode
> 
> d) if R1 is DRB on a link, R1 will not decapsulate anything 
> onto the link from ingress R2 unless
> R1 has received an LSP from R2 and all pseudonodes that R2 
> claims to be attached to, and that R2 claims to be DRB for
> 
> e) when R1 first comes up, it waits some amount of time on a 
> link before deciding that it is DRB (several Hello 
> intervals), and after becoming DRB, it still does not forward 
> data off the link until it has synchronized LSP databases 
> with its neighbors. "Synchronizing" 
> means that it receives
> a CSNP from the neighbor, and winds up with LSPs at least as 
> up-to-date as those reported in that CSNP. (Note: I think it 
> would be a good idea to have a flag in the Hello message 
> saying "I'd like to receive a CSNP from you" in case the 
> neighbor sent one and it got lost -- on a LAN, the DRB should 
> be sending them periodically, but if we have pt-to-pt links 
> at least in current IS-IS, CSNPs are not sent periodically, 
> though we could say RBridges should send them periodically on 
> pt-to-pt links.)
> 
> So...is this pretty much everyone's understanding of how it 
> should work?