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RE: [PWE3] Proposed change to 5..4.1 of PWE3 architecture
Stewart,
Since we no longer have a PSN convergence layer either in IP or in MPLS,
I suggest we remove it altogether.
In reference to:
As a special case, if the PW Demultiplexer is an MPLS label, the
protocol architecture of section 5.4.2 can be used instead of the
protocol architecture of this section.
I find this disturbing. Either people have the ECMP or ECMP-like problem
here as well or they don't. If they do we should better know this in
advance on not find out after another year has passed.
Following that, I suggest that we change the layering diagram such that
the layers include only: Physical, Data-link, PSN, PW-Multiplexing,
Payload Convergence, Payload (where payload convergence include timing,
sequencing, etc but the decomposition is not explicitly shown on the
figure). The payload convergence includes RTP and the control word.
We write a single architecture layer section which is good for both IP
and MPLS, since we don't specify the internal order of RTP and Control
word within the convergence layer in this section.
We write another section that describes the Convergence layer
decomposition and specify (unfortunately) that the RTP and control word
order changes depending on the demulplexing layer. If MPLS is used as
demultiplexing layer RTP is after control word, else RTP before control
word, or whatever)
Regards
Ron
> -----Original Message-----
> From: pwe3-admin@ietf.org [mailto:pwe3-admin@ietf.org] On
> Behalf Of Stewart Bryant
> Sent: Friday, March 19, 2004 8:37 AM
> To: pwe3@ietf.org
> Subject: [PWE3] Proposed change to 5..4.1 of PWE3 architecture
>
>
> After discussions with Yaakov Stein regarding the use of UDP/IP
> as a PW mechanism (used by both TDM approaches), it is proposed
> that 5.4.1 be amended as shown below.
>
> Is this acceptable to the WG?
>
> - Stewart
>
> New text:
>
> 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 can be used instead of the
> protocol architecture of this section.
> ==============================================================
> =========
>
> For reference the following is the text that appears in the -06 draft.
>
> 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-----------+->| As
> Needed |
> 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. (It
> is accepted
> that there MAY sometimes be good reason not to follow
> this rule, but
> the exceptional circumstances need to be documented in the
> Encapsulation Layer definition for that payload type).
>
> Where appropriate, timing is provided by RTP [RFC3550], which when
> used also provides a sequencing service. PW Demultiplexing may be
> provided by a number of existing IETF tunnel protocols. Some of
> these tunnel protocols provide an optional sequencing service.
> (Sequencing is provided either by RTP, or by the PW Demultiplexer
> Layer, but not both).
>
> RTP is normally carried over UDP, however the tunnel
> protocols that
> are capable of carrying a PW, provide sufficient functionality to
> carry RTP without an intervening transport layer. UDP
> MAY therefore
> be omitted from the protocol stack.
>
> A PSN Convergence Layer is not needed, because all the tunnel
> protocols shown above are designed to operate directly over an IP
> PSN.
>
> As a special case, if the PW Demultiplexer is an MPLS label, the
> protocol architecture of section 5.4.2 can be used instead of the
> protocol architecture of this section.
>
> ==============================================================
> ===========
>
>
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