[rbridge] per-VLAN instances of IS-IS
Eric Gray (LO/EUS)
eric.gray at ericsson.com
Wed Jun 20 13:21:44 PDT 2007
Radia, et al,
I was not challenging consensus on multi-pathing, for either
unicast or multicast. What I was objecting to was the assertion
that we ONLY do ECMP in "core" RBridges - which Silvano had stated
as if a WG decision. Since I seriously doubt that we could ever
arrive at a consensus as to exactly what sort of real-world device
would be a "core" RBridge, I don't think we have concluded that we
ONLY do <anything you choose to talk about> in such a beasty.
See Silvano's original comments toward the very end of this
> -----Original Message-----
> From: Radia Perlman [mailto:Radia.Perlman at sun.com]
> Sent: Wednesday, June 20, 2007 4:00 PM
> To: Anoop Ghanwani
> Cc: Eric Gray (LO/EUS); Silvano Gai; rbridge at postel.org
> Subject: Re: [rbridge] per-VLAN instances of IS-IS
> I'm also assuming we are doing multipathing, not just of unicast, but
> also multicast.
> Anoop Ghanwani wrote:
> > Personally, I would like the group to get to a
> > consensus on the ECMP issue fairly quickly.
> > I too, just like Silvano, thought it was going
> > to be done.
> > Anoop
> >> -----Original Message-----
> >> From: Eric Gray (LO/EUS) [mailto:eric.gray at ericsson.com]
> >> Sent: Wednesday, June 20, 2007 7:29 AM
> >> To: Silvano Gai; Anoop Ghanwani
> >> Cc: rbridge at postel.org; Radia Perlman
> >> Subject: RE: [rbridge] per-VLAN instances of IS-IS
> >> Silvano,
> >> Yes, that was probably discussed earlier in May.
> >> AFAIK, discussion != consensus.
> >> Possibly your customers need to explain to you that the
> >> difference between "core" and "not core" is not always as
> >> clear cut as you apparently think it is. Nor is it
> >> necessarily going to be simple for a device to determine
> >> which of the available equal cost paths only contain core elements.
> >> Also, ECMP - at least in the traditional sense - takes
> >> place where equal costs exist in a "routing" domain. That is
> >> at least as likely to occur in locii containing one or more
> >> edge components, as it is anywhere else.
> >> There are certainly limited applications - typically
> >> requiring careful configuration to restrict ECMP-like
> >> activity to very specifically defined equal cost paths -
> >> where it will be possible to say "we do ECMP only in the
> >> core." I personally wonder why link-bundling wouldn't be a
> >> better solution in those cases, however.
> >> Thanks!
> >> --
> >> Eric Gray
> >> Principal Engineer
> >> Ericsson
> >>> -----Original Message-----
> >>> From: Silvano Gai [mailto:sgai at nuovasystems.com]
> >>> Sent: Tuesday, June 19, 2007 11:39 PM
> >>> To: Eric Gray (LO/EUS); Anoop Ghanwani
> >>> Cc: rbridge at postel.org; Radia Perlman
> >>> Subject: RE: [rbridge] per-VLAN instances of IS-IS
> >>> Importance: High
> >>> We had this discussion on May 8th, 2007 on this mailing list.
> >>> In a nutshell: we do ECMP only in the core, but we don't
> >> learn in the
> >>> core, so I don't see the problem.
> >>> -- Silvano
--- SNIP ---
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