North American Network Operators Group
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Re: Question about propagation and queuing delays

  • From: Patrick W. Gilmore
  • Date: Mon Aug 22 11:47:29 2005 
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