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Re: [rtcweb] Review of draft-ietf-rtcweb-rtp-usage

Bernard Aboba <bernard.aboba@gmail.com> Thu, 08 May 2014 18:17 UTC

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From: Bernard Aboba <bernard.aboba@gmail.com>
Date: Thu, 08 May 2014 11:17:30 -0700
To: Emil Ivov <emcho@jitsi.org>
Archived-At: http://mailarchive.ietf.org/arch/msg/rtcweb/eDmvo7xRGhzOKFR8jH8jxZXk1h4
Cc: "rtcweb@ietf.org" <rtcweb@ietf.org>, Colin Perkins <csp@csperkins.org>
Subject: Re: [rtcweb] Review of draft-ietf-rtcweb-rtp-usage
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> On May 8, 2014, at 9:47 AM, Emil Ivov <emcho@jitsi.org> wrote:
>> 
>> The circuit breaker is a mechanism of last resort. If we've designed
>> it correctly, it will only stop sessions that are otherwise unusable.

[BA] Unusable at a given moment could change to usable later, either as a result of congestion control support and/or changing conditions. So it is one thing to stop sending for some period and indicate to the user that difficulties are being experienced then try again after backing down the send Bw, and another to stop and require a redial. 

> 
> This is another part that bothers me with circuit breakers. If there's a reasonable chance that a "redial" would succeed then why did we break the session? If not then why are we encouraging it?

[BA] As specified, circuit breakers is vulnerable to routing transients. Other transports such as TCP are explicitly designed to survive this, but circuit breakers will not.  So we need to ask ourselves why TCP never needed (or considered) such a mechanism.

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