Subject: [Fwd: RE: Proposed change to 5..4.1 of PWE3 architecture]

From: Stewart Bryant <[email-masked]>
Date: Tue, 23 Mar 2004 16:31:00 +0000

I lost track in some of the thread that followed this.

Sasha wants references to UDP, L2TP etc. These I can add.

There was some discussion about control protocols for UDP.
These are not excluded by the proposed text, and we do
not have a proposal for such a protocol.

I think that you all agreed that although not optimal
the text is technicall correct.

Can we live with this and move on?

If not, please can we focus on specific edit proposals
to this section.

Thanks

Stewart

-------- Original Message --------
Subject: RE: [PWE3] Proposed change to 5..4.1 of PWE3 architecture
Date: Mon, 22 Mar 2004 09:35:29 +0000
From: Stewart Bryant <[email-masked]>
Reply-To: [email-masked]
Organization: Cisco Systems, Inc.
To: [email-masked] <[email-masked]>

Following Ron's input, the proposed new text for 5.4.1 is:

5.4.1. PWE3 over an IP PSN

    The protocol definition of PWE3 over an IP PSN should employ existing
    IETF protocols where possible.

        +---------------------+              +-------------------------+
        |      Payload        |------------->| Raw payload if possible |
        /=====================\              +-------------------------+
        H Payload Convergence H-----------+->|     Flags, seq # etc    |
        H---------------------H          /   +-------------------------+
        H       Timing        H---------/--->|            RTP          |
        H---------------------H        /     +-------------+           |
        H     Sequencing      H----one of    |             |
        \=====================/        \     |             +-----------+
        |  PW Demultiplexer   |---------+--->|     L2TP, MPLS etc.     |
        +---------------------+              +-------------------------+
        |  PSN Convergence    |------------->|       Not needed        |
        +---------------------+              +-------------------------+
        |        PSN          |------------->|            IP           |
        +---------------------+              +-------------------------+
        |      Data-link      |------------->|         Data-link       |
        +---------------------+              +-------------------------+
        |       Physical      |------------->|          Physical       |
        +---------------------+              +-------------------------+

      Figure 10: PWE3 over an IP PSN

    Figure 10 shows the protocol layering for PWE3 over an IP PSN. As a
    rule, the payload should be carried as received from the NSP, with
    the Payload Convergence Layer provided when needed.  However in
    certain circumstances it may be justifiable to transmit the payload
    in some processed form. The reasons for this must be documented in
    the Encapsulation Layer definition for that payload type.

    Where appropriate, explicit timing is provided by RTP [RFC3550],
    which when used also provides a sequencing service.  When the PSN is
    UDP/IP, the RTP header follows the UDP header and precedes the PW
    control field, while for all other cases the RTP header follows the
    PW control header.

    The encapsulation layer may additionally carry a sequence number;
    sequencing is to be provided either by RTP, or by the PW
    encapsulation layer but not both.

    PW Demultiplexing is provided by the PW label, which may take the
    form specified in a number of IETF protocols,  e.g. an MPLS label, an
    L2TP session ID, or a UDP port number.

    When PWs are carried over IP the PSN Convergence Layer will not be
    needed.

    As a special case, if the PW Demultiplexer is an MPLS label, the
    protocol architecture of section 5.4.2 must be used instead of the
    protocol architecture of this section.

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

This differs from the previous CHANGED text in the last sentence in that
it used to read "section 5.4.2 can be used" and now reads "section 5.4.2
must be used"