[rbridge] Ambition with different VLAN configurations

[Dinesh G Dutt]

Hi Radia,

Some comments.

Radia Perlman wrote:
> 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)???
>
>   
VLAN 1 and I prefer it to be the only one, but maybe configurable. The 
frame must be tagged, not untagged as it leads to all kinds of corner 
cases.
> b) it will be a MUST to listen to spanning tree messages and include the 
> root bridge ID
> in the pseudonode LSP. Also,
>
>   
Will it need to support both (three if you include the currently 
dominant model, Cisco's) spanning tree protocols, IEEE STP and MSTP 
(Cisco's PVST is IEEE's STP run per VLAN).
> 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
>   
Need to think through this one.
> 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
>   
Need to think through this one.
> 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" 
>   
This could cause a significant delay in bringing an RBridge up and how 
things work when a network is powered down and comes up. I'm not sure 
about this part yet.

Dinesh

-- 
We make our world significant by the courage of our questions and by 
the depth of our answers.                               - Carl Sagan