Subject: Label distribution mode

From: "Vijayanand C" <[email-masked]>
Date: Wed, 18 Apr 2001 14:34:01 +0530

Hello,
I have a question in LDP.

Suppose, we have a per-platform label space entity bound to PPP and Ethernet
interfaces. Assume that the entity has been configured for Downstream on
demand and a session is already established with a peer. Now, while
establishing a new session with another peer, if that peer says Unsiolicited
mode in the Init message then the RFC says that we have to use Unsolicited
only. However the entity has been configured for ON-DEMAND and a session
with another entity is already running for that entity. How do we handle
this situation? Should we have another enity for this session and have a
one-to-one relationship between entity and session. Or can we treat this as
mis-configuration and reject the session establishment attempt.

Regards,
Vijay

---

From: Eric Gray <[email-masked]>
Date: Wed, 18 Apr 2001 16:42:02 -0400

Vijay,

    This should not be a problem for a number of reasons.  In
the worst case (an implementer has interpreted the meaning of 
the per-platform label space to mean that all labels are treated 
the same regardless of whether or not they apply to the same 
pair of peers) the labels that have been given to the previous
peer would (in at least some cases) have to be given to the new 
peer as well.  The only difference that would come out of the 
label distribution mode (DU verses DoD) would be whether or not 
the LSR has to wait to be asked to distribute those labels.  In 
some implementations, the prior use of labels is a complete non-
issue because the scope of per-platform labels can be restricted 
to a pair of peers.

    See http://www.mindspring.com/~ewgray/faq.htm#PPLAT for a
discussion of general issues relating to the per-platform label
space.

    Is it possible that you have reversed the sense of how labels
are distributed with repect to a label space?  Advertising the 
per-platform label space restricts the labels you can distribute,
not the labels you can receive in a distribution.  The fact that 
an LSR may have gotten labels from another peer with whom it had
advertised the per-platform label space, does not prevent it from
getting and using the same labels from an entirely different peer.

--
Eric Gray