Subject: Re: [mpls-tp] -03 of requirements draft & actions still to beresolved

From: "Eric Gray" <[email-masked]>
Date: Mon, 26 Jan 2009 16:32:49 -0600

Eric >> - Congruently Routed and associated at the Node level
Eric >>
Eric >> Where the distinction between the latter two cases is as
Eric >> shown in your list above (independent verses simultaneous)
Eric >> in the signaling case, and as follows in the configuration
Eric >> case:
Eric >>
Eric >> - If associated at the Layer Network level, there is some
Eric >>   logical construct that associates the two bi-directional
Eric >>   MPLS-TP LSPs, configured at LSP termination nodes.
Eric >> - If associated at the Node level, a similar construct is
Eric >>   needed at each node along the MPLS-TP LSP.
Eric >> 
Eric >> Note that the above (configuration) constructs may very well
Eric >> be required even if MPLS-TP LSPs are universally signaled.

NH=> What do mean by 'some logical construct'?  Just trying to
understand your intent here....can you give me an example?

Hmmm answered the wrong question in as separate mail.  To avoid
messing this up any further, here's the answer I meant to provide
for this question...

Certainly.

What does it mean to have a bi-directional LSP?  Is this just a 
convenient notion, an interesting concept that we can talk about
all day, or is it important because having such a thing makes it 
possible for something - presumably a client, or higher level 
service to treat this construction as a single entity?

I assume the purpose is the latter and - in fact - know that to 
be the case in at least some important areas.  If I want to treat 
a bi-directional set of whozits (E-G. - LSPs) as a single whatzit
(interface), something needs to perform that mapping.

The question I was trying illustrate was whether this mapping (or
one like it) is present only at the whozit end-points, or at each
node along the path.  

If you assume signaling, the existence of this mapping at each node
(in some cases at least) is implicit in the model where congruency 
is assured on a node-by-node basis.  Similarly, the existence of
such a mapping is implicit at end-points if signaling is used, even
in the case where congruency is assured only by end-points.

In the configuration case, the association is obviously not implicit 
and must therefore be made explicit.
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