Subject: [AVT] Commetns on Header compression for MPLS LSPs (draft-ash-avt-ecrtp-over-mpls-protocol-00.txt)

From: Magnus Westerlund <[email-masked]>
Date: Mon, 08 Mar 2004 15:50:11 +0100

Hi,

Having reviewed the solutions proposal document I would like to take a 
few steps back, and discuss the issues on a higher level. We should also 
not be carried into to much detail yet until the requirements work is 
completed.

In my understanding we will need a few components in the total system.

A. A signalling protocol for an MPLS ingress router (A) to 
determine/create the LSP that will go to a HC enabled egress router (B). 
That protocol seems to need to signal the following information:
- What HC algorithms it support
- What LSP that will go from A->B and for HC algorithms that uses 
feedback the return path B->A, which indicates HC enabled packets.
- Further HC algorithm parameters, for example maximum number of session 
contexts.

B. To create a mapping for the HC algorithm into the LSP. Here it seems 
that ECRTP would need to have identifiers for its packet types, while 
ROHC would not need anything.

The solution does not require anything more as I see it. It can be 
enhanced with description of how an ingress router determines what flows 
to do HC on, for example through the header compression hints that exist 
for RSVP, see RFC 3006. An ingress router can also use heuristics or any 
other method it desires to determine if it should apply header 
compression on a certain packet flow. Thus I don't see a need to talk 
about specific applications of RTP or UDP that can benefit from this work.

Something else that I reacted to in the draft was the indication that 
one needs to actually use a signalling session context identifiers. As I 
understand it, a compressor simply selects one from the available pool 
and establish it using a full context packet.

Cheers

Magnus Westerlund

Multimedia Technologies, Ericsson Research EAB/TVA/A
----------------------------------------------------------------------
Ericsson AB                | Phone +46 8 4048287
Torshamsgatan 23           | Fax   +46 8 7575550
S-164 80 Stockholm, Sweden | mailto: [email-masked]

This communication is confidential and intended solely for the addressee(s). Any unauthorized review, use, disclosure or distribution is prohibited. If you believe this message has been sent to you in error, please notify the sender by replying to this transmission and delete the message without disclosing it. Thank you.

E-mail including attachments is susceptible to data corruption, interruption, unauthorized amendment, tampering and viruses, and we only send and receive e-mails on the basis that we are not liable for any such corruption, interception, amendment, tampering or viruses or any consequences thereof.

_______________________________________________
Audio/Video Transport Working Group
[email-masked]
https://www1.ietf.org/mailman/listinfo/avt