[rbridge] Avoiding sending multiple IS-IS Hellos tagged with allthe VLAN tags

[Radia Perlman]

I don't understand that problem. What you're describing might argue for 
bridges using a unique
spanning tree per VLAN in order to optimize traffic flow for that VLAN, 
but I don't
see what it has to do with wanting to partition VLANs.

Radia


Dinesh G Dutt wrote:
> Radia Perlman wrote:
>> I'd like to understand what problem customers are attempting to solve 
>> with
>> partitioned VLANs, and what hardship it would present to require at 
>> least one of the
>>   
> The primary problem with having a VLAN everywhere is that the root of 
> the spanning tree moves around leading to non-optimal forwarding in 
> enterprise networks. Enterprise networks are carefully engineered 
> networks and in the event of failure, they want to localize the 
> effects as much as possible. So, they want each VLAN to be localized 
> and roots where they want it to be. Having a common VLAN messes up 
> that arrangement. Also, VLAN 1 is the default VLAN when a switch comes 
> up and there is typically lots of customer data on it.
>> VLANs to *not* be partitioned. With TRILL, if a customer eventually 
>> replaces
>> all bridges, the customer will not be able to partition VLANs anymore.   
> As I raised it in the meeting, this is a side-effect that has not been 
> considered before and needs to be carefully thought through. I don't 
> think many people are aware of this issue with TRILL that doesn't 
> exist with 802.1Q bridges today.
>> Also, from
>> what Anoop was explaining to me, the GVRP protocol would automatically
>> configure the switch-to-switch links to join all the islands of 
>> VLANs. So it would
>> seem as though it can't be that fatal to solving customer problems to 
>> require
>> *one* VLAN on a layer 2 cloud to not be partitioned.
>>   
> GVRP is not deployed by a significant majority of customers.
>
> Dinesh
>