[83691] in North American Network Operators' Group
Re: Question about propagation and queuing delays
daemon@ATHENA.MIT.EDU (Tony Finch)
Mon Aug 22 12:26:17 2005
Date: Mon, 22 Aug 2005 17:23:51 +0100
From: Tony Finch <dot@dotat.at>
To: Petri Helenius <pete@he.iki.fi>
Cc: David Hagel <david.hagel@gmail.com>,
"Robert E. Seastrom" <rs@seastrom.com>,
Richard A Steenbergen <ras@e-gerbil.net>, nanog@merit.edu
In-Reply-To: <4309EF53.7080408@he.iki.fi>
Errors-To: owner-nanog@merit.edu
On Mon, 22 Aug 2005, Petri Helenius wrote:
> David Hagel wrote:
>
> > This is interesting. This may sound like a naive question. But if
> > queuing delays are so insignificant in comparison to other fixed delay
> > components then what does it say about the usefulness of all the
> > extensive techniques for queue management and congestion control
> > (including TCP congestion control, RED and so forth) in the context of
> > today's backbone networks? Any thoughts? What do the people out there
> > in the field observe? Are all the congestion control researchers out
> > of touch with reality?
>
> Co-operative congestion control is like many other things where you're better
> off without it if most of "somebody else" is using it. TCP does not give you
> optimal performance but tries to make sure everybody gets along.
TCP performs much better if queueing delays are short, because that
means it gets feedback from packet drops more promptly, and its RTT
measurements are more accurate so the retransmission timeout doesn't get
artificially inflated.
Tony.
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