Subject: Re: guaranteed rate service specification

From: Scott Shenker <[email-masked]>
Date: Thu, 13 Jul 1995 18:58:41 PDT

Just a quick reply to one comment:

> There is a clear contradiction in the ID as Pawan point out. If the end
> systems don't adapt, then there is no point in sending in bursts into
> the network (i.e. having a non-zero token bucket). If they do adapt, then
> guaranteed service will take over from `predictive' service ;-0
> So, either predictive service has to go, or guaranteed service might
> as well be CBR (we'd like that)

It is true that for a nonadaptive flow there is no benefit to that flow
in sending in bursts.  However, the utilization of the network as a
whole can be improved if such bursts are allowed, since these bursts
can use up extra bandwidth when it is available.  If you take all of
the bursts out before sending the packets, then the packets have tighter
delay requirements at each node.  If you send the bursts in, then the
network has greater flexibility in when each packet is sent.  We hope
to quantify this increase in utilization soon.

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From: Pawan Goyal <[email-masked]>
Date: Fri, 14 Jul 1995 09:06:39 -0500 (CDT)

> to quantify this increase in utilization soon.

Does this imply that a network should give  a nonadaptive application
some incentive to send bursts ? It was my understanding that
if b_1 < b_2 then a source with profile (r,b_1) would be a "charged" less
than a source with  (r,b_2).

Pawan

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From: Zheng Wang <[email-masked]>
Date: Fri, 14 Jul 95 17:09:53 +0100

> to quantify this increase in utilization soon.

This is true for nonadaptive applications using guaranteed
services. However, if an adaptive application chooses to use
a guaranteed service (I dont see any reasons why not),
allowing bursts into the network will reduce e2e delay when
the network has sparse resources.

Although the service types should be derived from the
characteristics of major applications, I believe that
a service type should be not tied to the applications from
which which it was derived. The users/applications will decide
what service to use based on a wide range of consideration.
One may have particular reasons to use guaranteed services for
email or ftp.

Cheers
Zheng