Subject: [Tsvwg] ECN and unreliable transport

From: "Ingemar Johansson S \(LU/EAB\)" <[email-masked]>
Date: Wed, 18 Apr 2007 12:11:41 +0200

Hi

I wonder if there is any specific work ongoing with regards to ECN for unreliable transport such as UDP. I've seen that this is mentioned every here and there but I have not sofar seen any specific reports on this matter.
Any help on this subject is much appreciated.

Regards
Ingemar
*******************************************
Ingemar Johansson
Senior Research Engineer
EAB/TVP - Multimedia Technologies Ericsson Research
Ericsson AB
Box 920
S-971 28 Luleå, Sweden
Tel: +46 (0)8 4043042
ECN: 850-43042
Mobile: +46 (0)730 783289
MSN: [email-masked]
*******************************************

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From: Sally Floyd <[email-masked]>
Date: Wed, 18 Apr 2007 09:54:49 -0700

> I wonder if there is any specific work ongoing with regards to ECN for 
> unreliable transport such as UDP. I've seen that this is mentioned 
> every here and there but I have not sofar seen any specific reports on 
> this matter.

My own assumption is that ECN will be of great benefit for unreliable 
transport;
ECN is used the the new unreliable transport protocol DCCP
("http://www.read.cs.ucla.edu/dccp/").

However, my own view is that it would not be wise to add ECN to UDP at 
this time;
this is discussed in Section 3.1.2 of RFC 4336 
("http://www.ietf.org/rfc/rfc4336.txt").

- Sally
http://www.icir.org/floyd/

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From: "Ingemar Johansson S \(LU/EAB\)" <[email-masked]>
Date: Thu, 19 Apr 2007 08:42:05 +0200

Hi

Thanks for the reply, regarding the opinion about ECN for UDP. Read
section 3.2.1 in RFC4336 and  the arguments against this usage are 

UDP sockets: While I agree that this might be a issue for 3rd party
implemenetations running in a particular OS (Windows, Linux..) it does
not need to be a problem in e.g a mobile terminal.

Feedback: If the socket issue is solved I agree that there is no ECN
specific feedback for UDP, one could however base RTCP feedback on this
but this will probably be very easy to cheat. For walled garden
approaches such as IMS I beleieve that this is a smaller problem
however. I can agree that this is only a second best approach but it
seems to me that the industry is _very_ fond of UDP so a design that can
make use of ECN would actually be good even though it is not 100% idiot
proof.

Agree that the design of a new clean transport protocol would be alot
better though...

Ingemar

> -----Original Message-----
> From: Sally Floyd [mailto:[email-masked]] 
> Sent: den 18 april 2007 18:55
> To: Ingemar Johansson S (LU/EAB)
> Cc: [email-masked]
> Subject: Re: [Tsvwg] ECN and unreliable transport
> 
> My own assumption is that ECN will be of great benefit for 
> unreliable transport; ECN is used the the new unreliable 
> transport protocol DCCP ("http://www.read.cs.ucla.edu/dccp/").
> 
> However, my own view is that it would not be wise to add ECN 
> to UDP at this time; this is discussed in Section 3.1.2 of 
> RFC 4336 ("http://www.ietf.org/rfc/rfc4336.txt").
> 
> - Sally