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Re: [aqm] Question re draft-baker-aqm-recommendations recomendation #2

Linda Dunbar <linda.dunbar@huawei.com> Mon, 29 April 2013 22:29 UTC

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From: Linda Dunbar <linda.dunbar@huawei.com>
To: John Leslie <john@jlc.net>
Thread-Topic: [aqm] Question re draft-baker-aqm-recommendations recomendation #2
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Date: Mon, 29 Apr 2013 22:28:59 +0000
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Cc: "Fred Baker (fred)" <fred@cisco.com>, "aqm@ietf.org" <aqm@ietf.org>
Subject: Re: [aqm] Question re draft-baker-aqm-recommendations recomendation #2
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>    I don't follow your point here. There are cases where ECN marking
> may not work very well, but I don't see any correlation to the size
> of the network. (ECN signals reach a receiving endpoint unless
> something
> is broken.)
> 


[Linda] Congestion can be transient. For a network with many hops, the congestion might not exist anymore by the time the Source nodes receive the notification from the end points. 
When many source nodes throttle back traffic (or control ingress rate) for transient congestion, network oscillation can occur, which is not good. 

Network can perform much better if there are two different types of congestion marking, one for transient congestion, and another one for congestion caused by "hard degradation" (e.g. LAG link member failure, or microwave link bandwidth being reduced due to weather, etc). 


Linda

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