Re: Label Set Object

["Adrian Farrel" <afarrel@movaz.com>]

Suppose (just suppose) that I want a unidirectional sonet LSP and that I want to
constrain the label choice to a specific value.  Note that this is distinct from
the question of what labels to use in each direction for bidirectional.
It is clear how I signal it.  No issues. Label Request, Label Set with one
member...

Now suppose I also want a bidirectional sonet LSP.
How do I indicate that it is bidirectional?
I  believe the only method is to include an Upstream Label.

Could we say that bidirectional uses Upstream Label only, and unidirectional
uses Label Set only?
Yes.

Would that be a good idea?
I don't see think that having multiple choices of presence of objects is useful.

Could an implementation choose to ignore one of the objects and act only on the
other?
Of course.

Adrian

----- Original Message -----
From: "John Drake" <jdrake@calient.net>
To: "'Anca Zamfir'" <ancaz@cisco.com>; "Zafar Ali" <zali@cisco.com>
Cc: "'Juneja, Manoj'" <m_juneja@trillium.com>; "Vinay Vernekar"
<vinay.vernekar@wipro.com>; "Manoj Agiwal" <ManojA@netbrahma.com>; "'Ccamp
(E-mail)" <ccamp@ops.ietf.org>; <skatukam@cisco.com>; "mpls@UU. NET (E-mail)"
<mpls@UU.NET>
Sent: Wednesday, May 08, 2002 10:42 PM
Subject: RE: Label Set Object


> Lou and I just reviewed section 5.1.1 of
> draft-ietf-mpls-generalized-rsvp-te-07.txt (rather than
> draft-ietf-mpls-generalized-signaling-08.txt, which is what I looked at this
> morning), and it's pretty clear.
>
> The upstream node processing the ERO for the outgoing link checks whether
> there are explicit label control subobjects for upstream or downstream.  An
> explicit label control for upstream is replaced in the ERO with an upstream
> label and an explicit label control for downstream is replaced with a label
> set with the same label.  This is so done so that there is only one
> mechanism for an upstream node to specify the downstream label; explicit
> label control is only used by a remote node.
>
> So the only question is whether for SONET/SDH LSPs, this mechanism is
> required.
>