[83688] in North American Network Operators' Group
Re: Question about propagation and queuing delays
daemon@ATHENA.MIT.EDU (Patrick W. Gilmore)
Mon Aug 22 11:45:50 2005
In-Reply-To: <4309F01B.3030903@ehsco.com>
Cc: "Patrick W. Gilmore" <patrick@ianai.net>
From: "Patrick W. Gilmore" <patrick@ianai.net>
Date: Mon, 22 Aug 2005 11:41:31 -0400
To: nanog@merit.edu
Errors-To: owner-nanog@merit.edu
On Aug 22, 2005, at 11:32 AM, Eric A. Hall wrote:
> On 8/22/2005 11:14 AM, 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?
>
> Latency is cumulative. Knocking a little time off Part A will still
> act to
> shorten total time, regardless of the time occupied by Part B
>
> Queuing behaviors are also significant when you are suffering
> congestion,
> apart from the delay factors
I think the key here is "when you are suffering congestion".
RS said that queueing delay is irrelevant when the link was between
60% and > 97% full, depending on the speed of the link. If you have
a link which is more full than that, queueing techniques matter.
Put another way, queueing techniques are irrelevant when the queue
size is almost always <= 1.
--
TTFN,
patrick
