Subject: RE: draft-raggarwa-rsvpte-pw-01.txt

From: "Gray, Eric" <[email-masked]>
Date: Wed, 30 Mar 2005 12:22:02 -0500

Yaakov,

	The time that it is necessary to use a protocol to
reserve resources is when it is possible the reservation
may fail. If it is not possible for resource reservation
to fail, then it does not make as much sense to reserve
resources in the first place.

	Why call ahead for a restaurant that never has a
waiting line?

	Given that it is possible for a reservation to fail 
along a path selected on some basis other than resource
availability (shortest path, for instance), how does it
make sense to separate the signaling into path selection
and resource reservation stages?

--
Eric 

-----Original Message-----
From: [email-masked] [mailto:[email-masked]]On Behalf Of
Yaakov Stein
Sent: Wednesday, March 30, 2005 12:05 PM
To: Nurit Sprecher; [email-masked]
Cc: pwe3; Stewart Bryant
Subject: RE: [PWE3] draft-raggarwa-rsvpte-pw-01.txt 

> Use the LDP to distribute the labels and establish the non-TE MS-PWs
and the RSVP-TE for distributing labels and establishing the TE MS-PWs.

> My question was why we should employ both LDP and RSVP-TE for TE
MS_PWs as you described in your mail (see below). 
> I did not mean to non-TE MS_PWs. For TE MS_PWs there is no use in
employing two protocols. 

Nurit, 

The question is whether to use, as you suggest, two different protocols
for PW label distribution
(i.e. LDP for some of the PWs, and RSVP-TE for others)
or whether to use the same label distribution protocol for all PWs, 
and to then run a second (different) protocol for resource reservation
for those PWs that need it.

I prefer not having to implement two different protocols for the
precisely the same function
(label distribution), but it is commonplace to run two or more different
protocols 
one after the other to perform distinct functions.

For example, when using LDP or RSVP-TE to set up MPLS LSPs, 
we first an IP routing protocol to find the topology, 
and afterwards the label distribution protocol to pin the LSP based on
that topology.

So applying your argument that only a single protocol should be used for

distinct sequential functions, would you suggest that we only allow BGP
setup of LSPs?

Y(J)S

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