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[AVT] Re: I-D ACTION:draft-ash-avt-ecrtp-over-mpls-protocol-00.txt


There are some operations that need to be able to distinguish
between IP and non-IP MPLS payloads. For example a router
performing ECMP based on the IP addresses or other information
in the IP header, or an IPFIX/PSAMP packet sampling system
that needs to analyse the payload contents.

We identified this need in PWE3 and proposed a solution. This
is described in sections 5.4.3 and 5.4.4 of the PWE3 Architecture
draft:

http://www.ietf.org/internet-drafts/draft-ietf-pwe3-arch-06.txt

In essence we proposed that the nibble that immediately follows
the MPLS bottom label has the following semantics:

Value Meaning
0 PWE3 payload*
1 Identified payload type (see below)
4 IPv4
6 IPv6

* It might be argued that this should be changed to mean
"unidentified payload type"

The identified payload type above is the first nibble
in a longword with the following definition:

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 1| reserved = 0 | PA | Protocol ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| As defined by PPP DLL protocol definition |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 14: PWE3 PID

The meaning of the fields of the PWE3 PID (Figure 14) is as follows:


PA protocol authority for the user plane or the control plane
protocol ID
0 = PPP DLL
1-15 = Reserved

Protocol ID
Protocol ID following the format defined by the protocol
authority identified in PA.

Bits 4 to 11 inclusive are reserved for future use and must be zero.

PWE3 currently describes this in terms of historic IP version numbers,
but IESG feedback is that we need to use a new registry.

The proposal is that there is a new "nibble that follows the MPLS
label" registry. This will still have the values and semantics described
above. A new draft describing this will be submitted when the IETF
embargo on new drafts lifts, and the PWE3 architecture draft modified accordingly. Note that this does not change the existing PWE3 protocol
or headers, just the way that we describe the protocol.

If this proposal gains approval, the implication for ecrtp-over-mpls
would be that it should either:

1) Run under first nibble 0
2) Run under first nibble 1 with an ecrtp-over-mpls as the PPP-DLL value
3) Request a first nibble value from the new registry

- Stewart


Curtis Villamizar wrote:

------- Blind-Carbon-Copy

To: "Ash, Gerald R (Jerry), ALABS" <gash@att.com>
cc: avt@ietf.org
Reply-To: curtis@fictitious.org
Subject: Re: I-D ACTION:draft-ash-avt-ecrtp-over-mpls-protocol-00.txt In-reply-to: Your message of "Mon, 09 Feb 2004 07:39:42 CST."
<9473683187ADC049A855ED2DA739ABCA0201F057@KCCLUST06EVS1.ugd.att.com> Date: Mon, 09 Feb 2004 11:28:58 -0500
From: Curtis Villamizar <curtis@workhorse.fictitious.org>


In message <9473683187ADC049A855ED2DA739ABCA0201F057@KCCLUST06EVS1.ugd.att.com>
, "Ash, Gerald R (Jerry), ALABS" writes:

All,

Please review and comment on 'Protocol Extensions for ECRTP over MPLS' http:/
/www.ietf.org/internet-drafts/draft-ash-avt-ecrtp-over-mpls-protocol-00.txt. The protocol extensions enable the use of MPLS to route enhanced compressed RTP (ECRTP) compressed packets over an MPLS LSP without compression/decompres
sion cycles at each router.

The proposed extensions are based on the requirements documented in 'Requirem
ents for ECRTP over MPLS' http://www.ietf.org/internet-drafts/draft-ash-avt-e
crtp-over-mpls-reqs-01.txt.

Thanks,
Jerry


Title : Protocol Extensions for ECRTP over MPLS
Author(s) : J. Ash
Filename : draft-ash-avt-ecrtp-over-mpls-protocol-00.txt
Pages : 0
Date : 2004-2-5


Jerry,

This looks to be a very good direction to go in.  I've dropped MPLS
from the Cc and put MPLS on the bcc so people know the discussion is
on the AVT mailing list only.

In your encapsulations you should make sure to avoid any values in the
first byte that could be mistaken as IPv4 or IPv6 or any of the
encapsulations being worked on by those working on VPN and PW.  See
"The PWE3 Control Word", Jonathan Stein, 22-Oct-02,
draft-stein-pwe3-controlword-00.txt, for some early discussion on
that.  Note though that "Payload Type" is something that many
providers require so that multipath can be used on IP traffic which
consitutes the majority of traffic yet reordering is avoided for
traffic which cannot be split based on what appears to be an IP header
and the IP src/dst pair.

It might be best to reserve a single fixed first byte for the "Packet
Type" (and I suggest you make up a name for this shim such as
SCID_Packet_Type) and use the second byte for the packet types that
you have defined.  Just as you have to get numbers for SCID_Request
Object and Header_Compression_Reply Object from IANA, you'll have to
coordinate with others over this number space, though it is less clear
if IANA is the authority on this quite yet.

Curtis

------- End of Blind-Carbon-Copy





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