Subject: PHP and architecture draft

From: Markus Jork <[email-masked]>
Date: Mon, 31 Jan 2000 12:36:34 -0500

I just noticed that the architecture draft (draft-ietf-mpls-arch-06.txt)
seems to be somewhat out of sync with reality.
The section on penultimate hop popping says:

"Initial label distribution protocol negotiations MUST allow each LSR to determine whether its neighboring LSRS are capable of popping the label stack. A LSR MUST NOT request a label distribution peer to pop the label stack unless it is capable of doing so."

Looking at the current label distribution protocols (RSVP and LDP), none of
them seems to provide the allegedly mandatory feature to figure out whether
a peer is capable of doing PHP.

So what should we do about this issue:
a) agree that I have misread the I-Ds and just ignore my message,
b) change the "MUST" in the architecure document to a "SHOULD"
c) or just ignore this section of the architecture document?
Fixing the signalling protocols to provide the feature seems to be too bothersome.

Markus

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From: Yoshihiro Ohba <[email-masked]>
Date: Tue, 01 Feb 2000 11:18:22 +0900

Markus,

The issue was once discussed on the mailing list, and 
the following paragraph was added to section 5 of the LDP
specification.  

     - Section 2.16 of the MPLS architecture [ARCH] requires that the
       initial label distribution protocol negotiation between peer LSRs
       enable each LSR to determine whether its peer is capable of
       popping the label stack.  This version of LDP assumes that LSRs
       support label popping for all link types except ATM and Frame
       Relay.  A future version may specify means to make this
       determination part of the session initiation negotiation.

Hope this helps.
Yoshihiro Ohba