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

[Anoop Ghanwani]

Hi Silvano,

Believe it or not there are customers out there that
use GVRP.  They might not be a majority, but they
do exist.

As far as I'm aware, it is _not_ very common
for customers to be reusing VLAN IDs within the
enterprise.  If they do reuse them, they are in
physically separate portions of the network that
are interconnected by routers.  That's the normal
tiered architecture that one tends to see in 
enterprises.

I have never come across a customer that uses
partitioned VLANs the way you mention, so I find
it hard to believe they are common.  There's always
the oddball, strange architecture out there.
Do we really need to force everyone to send per-VLAN
hellos to deal with that?  We can always design to
make that type of configuration work, but we should
optimize for the common case.

Anoop

> -----Original Message-----
> From: rbridge-bounces at postel.org 
> [mailto:rbridge-bounces at postel.org] On Behalf Of Silvano Gai
> Sent: Tuesday, July 31, 2007 2:40 PM
> To: Radia Perlman; Dinesh G Dutt
> Cc: rbridge at postel.org
> Subject: Re: [rbridge] Avoiding sending multiple IS-IS Hellos 
> tagged withallthe VLAN tags
> 
> 
> Radia,
> 
> We are describing to you how VLANs are deployed today in 
> Enterprise networks. You may say that "you don't like it", we 
> may agree with you, but this does not change how they are deployed.
> 
> For RBridges to be successful they need to be able to replace 
> core bridges without messing up the existing network configurations.
> 
> Today most customers do not deploy VLANs end-to-end and they 
> do reuse VLANs number in different part of the enterprise. If 
> RBridges are not capable of supporting this, they are not attractive.
> 
> Remember that the #1 customer requirement we have for TRILL 
> is: "replace core bridges with RBridges to enable Equal Cost 
> Multi Path, all the rest MUST remain the same".
> 
> GVRP is not deployed; I am not sure which customers Anoop is 
> referring to.
> 
> -- Silvano
> 
> > -----Original Message-----
> > From: Radia Perlman [mailto:Radia.Perlman at sun.com]
> > Sent: Tuesday, July 31, 2007 11:19 AM
> > To: Dinesh G Dutt
> > Cc: Silvano Gai; rbridge at postel.org
> > Subject: Re: [rbridge] Avoiding sending multiple IS-IS Hellos tagged
> with
> > allthe VLAN tags
> > 
> > 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
> > >
> 
> 
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