Subject: [PWE3] RE: draft-ietf-pwe3-cesopsn-03.txt and draft-ietf-pwe3-satop-02.t xt

From: Sasha Vainshtein <[email-masked]>
Date: Tue, 26 Jul 2005 07:22:18 +0300

Hi Bill,
Yes indeed, placement of RTP header and Control Word in these drafts
differ between IP and MPLS encapsulations.

This issue has been discussed on the PWE3 mailing list, and this
arrangement is a result of the need tomeet to requirements:

- compliance with the traditional usage of RTP over IPv4/IPv6 PSN 

- MPLS ECMP avoidance (which is critical for TDM pseudo-wires) as
  described in draft-ietf-mpls-ecmp-bcp-01.txt and compliance with
  the requirement for the preferred and generic PWE3 control word
  formats (as defind in draft-ietf-pwe3-cw-05).

This is explicitly stated in the Note in Section 5.1 of 
draft-ietfp-we3-cesopsn-03.

For historical purposes I'd like to add that one of the arguments against
such a difference raised during the WG discussions was the fact that the
1st nibble of RTP header (should it directly follow the MPLS label
stack) is 8 or more. However, this argument has been rejected by the WG
because 8 is a registered (even if probably never used!) IP version
with IANA.

Hopefully this helps to clarify the situation.

Regards,
                         Sasha
-----Original Message-----
From: Bill Storer (bstorer)
To: [email-masked]; Sasha Vainshtein
Sent: 7/25/2005 10:34 PM
Subject: draft-ietf-pwe3-cesopsn-03.txt and draft-ietf-pwe3-satop-02.txt

Hi Sasha,
 
I'm a bit confused about the placement of the RTP header and control
word in these drafts.  For IP, we have the RTP header before the control
word.  For MPLS, we have the RTP header after the control word.  
 
Could you elaborate on the reasons for this difference?

Thanks,

Bill

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