[rbridge] New shim header proposal---without F-tag field
Eric.Gray at marconi.com
Wed Nov 1 13:11:13 PST 2006
I did not actually say that we need to support half a
million RBridges, I simply said that we may need to support
more than 32K (or even 64K), consequently I do not support a
reduction in the "name space" to 16 bits.
It would never work out to an order N^2 connectivity
in any case, so this concern - IMO - comes under the heading
of FUD. If every port needed to be connected to every other
port, then there would not be a need to have VLANs, and -
hence - no need to have separate per-VLAN instances. In a
real world application where VLANs are used to connect large
numbers of multi-port switches, only a few ports on a few
switches typically end up connected to each individual VLAN.
Some exceptions would occur, but they would be exceptions.
Thus per-VLAN connectivity would be a sparse partial mesh, or
VLANs would not be used.
This is in fact part of the justification for having
per-VLAN IS-IS instances. Trauma to part of the network is
only going to impact on routing convergence for the IS-IS
instances participating in affected VLANs.
--> -----Original Message-----
--> From: Silvano Gai [mailto:sgai at nuovasystems.com]
--> Sent: Wednesday, November 01, 2006 11:55 AM
--> To: Russ White
--> Cc: Gray, Eric; Radia Perlman; rbridge at postel.org
--> Subject: RE: [rbridge] New shim header proposal---without
--> F-tag field
--> What is a stretch is 32K trees of 32K nodes, which is what
--> you need if
--> you want to deploy the current TRILL proposal with 32K RBridges.
--> Eric says that we need to accommodate half a million RBridges.
--> Half a million tree of half a million nodes is unfeasible.
--> If we want to support such a large number of Rbridges, we
--> need to modify
--> the current Trill proposal, reducing the number of trees
--> that need to be
--> -- Silvano
--> > -----Original Message-----
--> > From: Russ White [mailto:riw at cisco.com]
--> > Sent: Wednesday, November 01, 2006 8:35 AM
--> > To: Silvano Gai
--> > Cc: Gray, Eric; Radia Perlman; rbridge at postel.org
--> > Subject: Re: [rbridge] New shim header proposal---without
--> F-tag field
--> > -----BEGIN PGP SIGNED MESSAGE-----
--> > Hash: SHA1
--> > >> I don't think there is consensus yet that we
--> only need 16 bits
--> > >> for RBridge IDs.
--> > >
--> > > With 16 bits, using 1 bit to indicate unicast, we can have 32K
--> > > According to the current definition of TRILL, there is
--> the need to
--> > > Djikstra on a database with 32K records, one time for the core
--> > > and 32K times for the IRTs. This is clearly out of
--> reach even for
--> > > most powerful CPU.
--> > ?? Perhaps 32k trees is a stretch, but 32k nodes in a
--> tree? I don't
--> > think that's really a stretch on today's processors, from
--> the scaling
--> > work I've seen done in IS-IS.
--> > :-)
--> > Russ
--> > - --
--> > riw at cisco.com CCIE <>< Grace Alone
--> > -----BEGIN PGP SIGNATURE-----
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--> > iD8DBQFFSMypER27sUhU9OQRAqLwAJ9FLN2YNP2mrB6i0ZcV1fxLzAT0hgCfYHYj
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--> > =kwzq
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