Subject: [mpls-tp] Network Layer and MS-PW - MPLS-TP weekly 26/01/2010

From: Stewart Bryant <[email-masked]>
Date: Mon, 25 Jan 2010 14:56:38 +0000

The agenda this week is to discuss the email that Malcolm sent to this 
list last Wednesday.

Co-ordinates are at the bottom of the email

- Stewart

=====================

Stewart,

Your  request for an informal review of section 3.4 of 
draft-ietf-mpls-tp-framework-07 was assigned to Q.12/15.  This review 
produced a number of comments.  Many of which were capture in a marked 
up document that was discussed today on the MPLS-TP call.  The results 
of that discussion have been posted to the MPLS-TP wiki 
 (_http://wiki.tools.ietf.org/misc/mpls-tp/attachment/wiki/meeting-notes/_). 

Two other significant comments arose that were not captured directly in 
the marked up document:

1)        Use of the term "Network Layer":
2)        Need for multi segment pseudo wires.

I have provide my view of the key points that were raised, I invite 
other ITU participants to add any points that I missed.

*Network Layer:*

A request was made to provide reference for how a 'network layer' 
protocol, as mentioned in sections 3.4.3, is defined.  Based on 
discussion today my understanding is that the term "network layer 
protocol" is used in RFC3031.  I think that this comment could be 
resolved if the authors can avoid using the term "Network Layer" and 
make it clear that the context for "Network Layer Protocol" is described 
in RFC 3031.

*Multi segment pseudo wire:*

The initial request was to provide the rational for the inclusion of 
multi segment PWs in MPLS-TP.
This provoked some further discussion (both on line and off line) that 
raised some questions and concerns over the use of PWs in general and in 
particular making the PW a layer network (in the G.800/G.805 sense) vs. 
restricting the role of the PW to providing client adaptation..  A 
summary of the points raised is provided below.

    * In an instance of an implementation of a MPLS-TP network the
      bottom label in the scope of that network may be either a PW label
      or an LSP label.
    * PWs uses T-LDP for signalling, it is my understanding that this is
      "in band" and relies on IP forwarding contrary to the
      requirements.  It is not clear what protocols are used for other
      control plane functions (e.g. routing, discovery).  LSPs use an
      out of band GMPLS control plane (as defined in the requirements).
    * T-LDP does not support traffic engineering
    * T-LDP requires extension to support multi segment PWs.  The scope
      of these extensions and the proposed routing protocols are not
      well understood within the ITU.
    * Tandem connection monitoring of a PW is achieved by pushing a
      (LSP) label and using the (server) LSP for PST monitoring (same as
      for a LSP).
    * Setting up a PW with traffic engineering and/or segment monitoring
      requires the use and coordination of both a T-LDP and a GMPLS
      control plane.

These issues could be either avoided or limited if we restrict the role 
of the PW to providing client adaptation at the edge of a MPLS-TP 
network and using LSPs in the core of the network.

We would very much appreciate your comments on these points.

Regards

Malcolm Betts
Co chair ad hoc on MPLS-TP

=====================

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Topic: MPLS-TP weekly
Date: Tuesday, January 26, 2010
Time: 4:00 pm, GMT Time (London, GMT)
Meeting Number: 206 491 157
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