Subject: Service disciplines for RSVP 7/08/95 7/11/95 08:14:29

From: "Roch Guerin ((914) 784-7038)" <[email-masked]>
Date: Tue, 11 Jul 95 13:30:12 EDT

Reference:  Your note of Tue, 11 Jul 1995 08:14:29 -0900 (PDT)

>Have you examined the effects on end-to-end jitter?  It
>seems that variation in the scheduling of packets with
>additional buffering required along the path will
>significantly impact jitter when network loads vary.  Any
>thoughts?

Jitter is actually tougher to control than delay as it requires
that you provide both upper and lower delay bounds.  Scheduling
disciplines help decouple delay (and jitter) guarantees from
the buffer size since they provide dynamic priorities.  However,
variations in network load still impact jitter (and delay) since
one packet could see hardly any delay and the next be delayed
by the maximum allowable value (bound).
In the case of a rate controlled service discipline,
it is not clear to me if letting packets go out early on an idle
link would actually trigger greated load variations and, therefore,
worsen jitter.  My first guess tells me that it may, but I'll need
to think more about it.
Roch

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From: Masataka Ohta <[email-masked]>
Date: Fri, 14 Jul 95 1:18:07 JST

> that you provide both upper and lower delay bounds.

Relativistic theory tells us that delay control is a lot tougher
(as tough as often just impossible) than jitter control.

In many intercontinental cases, specifying delay bound is just
meaningless.

Or, do you have FTL transport?

> However,

Preallocated time slots makes jitter control trivially easy.

							Masataka Ohta