Subject: Uni-directional Labels with Labels-RSVP over ATM

From: Andy Baker <[email-masked]>
Date: Mon, 10 Jan 2000 16:25:18 -0000

ATM hardware only typically only supports uni-directional labels, such that
when a label (A) is allocated for an upstream connection over a link, and
connected through to a second label (B) received over a downstream link,
establishing a data path from upstream through to the downstream link, then
the reverse direction is also set up.

This means that a bi-directional signalling protocol such as RSVP MUST not
allow the upstream machine to then assign the use of label A for a different
LSP downstream.

Typically this may be solved in several ways:

1. careful configuration of the range of labels which each box may allocate
labels from
2. dynamic determination or negotiation of the range of labels a box may use
(e.g. boxes using LDP compare their identifiers, and the box with the lesser
id only allocates even labels, that with the larger, odd labels
3. luck - try a label and if refused, try another one

I have not seen any attempt to address this for Labels - RSVP.

What are people's thoughts?

Andy 

--
Andy Baker  mailto:[email-masked]
ATM, MPLS and Telecoms Development Group
Data Connection Ltd., Chester, UK
http://www.datcon.co.uk/
Tel: +44 (0) 1244 313440  Fax: +44 (0) 1244 312422