Subject: Re: [Tsvwg] VoIP and Congestive Collapes: QoS vs. Best Effort

From: Sally Floyd <[email-masked]>
Date: Wed, 02 Jul 2003 22:27:30 -0700

>Are these two drafts trying to solve different problems? 

The two drafts are trying to solve different problems.

The IAB draft, draft-iab-congestion-00.txt, is not trying to say
that best-effort service is a good solution for VoIP traffic, or a
better solution than some form of QoS, or anything of the kind.
The IAB draft is trying to say that today some VoIP traffic in fact
runs as best-effort traffic over one or more links in the best-effort
Internet, and that this is likely to be the case in the near future
as well, and that it is not deemed recommended behavior by the IAB
for these flows to maintain their minimum sending rate in the
presence of persistent, steady-state packet drop rates experienced
by the flow.

We will try to be more clear, in the next round of revisions, that
we are not trying to say that we are recommending best-effort service
as the recommended path for roll-out for VoIP.  We are not recommending
any roll-out path one way or another.  We are observing that in fact,
VoIP traffic some times ends up competing, as best-effort traffic,
with other best-effort traffic in the Internet.

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

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From: Cyrus Shaoul <[email-masked]>
Date: Thu, 03 Jul 2003 19:07:28 -0400

Thanks a lot for clearing this up for me. I have a follow-on thought: I
think that one aspect that the two drafts do share is a need for certain
applications to abide by certain guidelines (for example, calls always
terminate when packet loss becomes unacceptable, or video calls never
exceed or their requested bandwidth utilization after being admitted.)

Do you know if there is a generic way to enforce these requirements on
applications? It seems to me that if the guidelines are not enforceable,
there will be a tendency to descend into the "tragedy of the Commons" in
all these scenarios. (Somebody will always hack a non-compliant version
that ignores packet loss, and then distribute to the Internet User it as
a "SuperPhone" or something like that.) Is this part of the larger
"end-to-end vs. active core" debate? Is this out of the scope of the
TSVWG?

Thanks again, 

Cyrus

On Wed, 02 Jul 2003 22:27:30 -0700
Sally Floyd <[email-masked]> wrote:

SF> >Are these two drafts trying to solve different problems? 
SF> 
SF> The two drafts are trying to solve different problems.
SF> 
SF> The IAB draft, draft-iab-congestion-00.txt, is not trying to say
SF> that best-effort service is a good solution for VoIP traffic, or a
SF> better solution than some form of QoS, or anything of the kind.
SF> The IAB draft is trying to say that today some VoIP traffic in fact
SF> runs as best-effort traffic over one or more links in the best-effort
SF> Internet, and that this is likely to be the case in the near future
SF> as well, and that it is not deemed recommended behavior by the IAB
SF> for these flows to maintain their minimum sending rate in the
SF> presence of persistent, steady-state packet drop rates experienced
SF> by the flow.
SF> 
SF> We will try to be more clear, in the next round of revisions, that
SF> we are not trying to say that we are recommending best-effort service
SF> as the recommended path for roll-out for VoIP.  We are not recommending
SF> any roll-out path one way or another.  We are observing that in fact,
SF> VoIP traffic some times ends up competing, as best-effort traffic,
SF> with other best-effort traffic in the Internet.
SF> 
SF> - Sally
SF> http://www.icir.org/floyd/
SF> 
SF> 
SF> 
SF> 
SF> _______________________________________________
SF> tsvwg mailing list
SF> [email-masked]
SF> https://www1.ietf.org/mailman/listinfo/tsvwg

Cyrus Shaoul
CEO
Tomigaia Inc.
http://www.tomigaia.com/
[email-masked]
646-645-6881