[rbridge] Proposal to make VLAN mapping work

[Dinesh G Dutt]

Option 2 is fine with me, Radia. We can extend it later, if need be.

Dinesh
Radia Perlman wrote:
> Dinesh, which of the alternative approaches to b) do you prefer, namely:
>
> 1) If RB1 notices X maps to Y, RB1 reports "X maps to Y" in its Hello,
> and there must only be one forwarder for the set {X,Y}, but all the 
> other VLANs
> can be divvied out to lots of other forwarders
>
> 2) If RB1 notices that any VLAN maps to any other VLAN, it simply
> sets a flag in its Hello saying "VLAN mapping is occurring on this 
> cloud",
> and there must be only one appointed forwarder for all VLANs on that 
> link.
>
> I personally prefer 2). I would have preferred only the DRB forward 
> to/from
> the link (simpler, safer) in all cases, but certainly if we say that 
> there can
> only be a single forwarder in the (hopefully rare) case where VLANs are
> being mapped within the link, that seems like not a big restriction.
>
> If we do 2), that means a whole lot information to encode in a Hello. 
> Just
> a flag "I've detected VLAN mapping". The alternative (1) requires 
> encoding
> which VLANs map to which other VLANs.
>
> Radia
>
>
>
>
> Dinesh G Dutt wrote:
>> Radia Perlman wrote:
>>  
>>> I think I understand what Caitlin is saying, and let me say it in 
>>> different words.
>>> What Caitlin is saying: Avoid VLAN mapping entirely by just
>>> renumbering the VLAN that needs to change.
>>>     
>> I understood the same. That's unfortunately not always the choice,
>>  
>>> So I think our options are:
>>> a) explicitly not support VLAN mapping. Declare it a 
>>> misconfiguration if it is detected, and
>>> make the network owner renumber things so no VLAN mapping is 
>>> occurring. (this is
>>> how the current spec reads)
>>> b) allow for support by changing the spec to include information in 
>>> IS-IS Hellos
>>> to alert the DRB that VLAN mapping is going on.
>>>
>>> So, anyway...I recommend we do "b", namely alert the DRB that VLAN
>>> mapping is going on, and have the DRB make sure there is only one
>>> forwarder for any mapped VLANs, and don't say anything else in the
>>> spec about VLAN mapping. That way there are sufficient hooks so
>>> that someone can implement VLAN mapping if they want.
>>>     
>> That is fine by me. That is why I believe you suggested documenting 
>> the other changes in a separate draft.
>>
>> Dinesh
>>
>>   
>
>

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