Subject: minimum policed unit

From: Alencar de Melo Junior <[email-masked]>
Date: Mon, 16 Mar 1998 15:36:21 -0300

Hi.

	I don't understand how the parameter m, minimum policed unit, defined
in Tspec, can be used. The Internet Draft "The Use of RSVP with IETF
Integrated Services" (J. Wroclaski) says:

"smaller values of this parameter may lead to incresead likelihood of
admission control failure". 

Why?

Thanks,

-- 
Alencar de Melo Junior.
Stadual University of Campinas/Brasil

---

From: JJ Krawczyk <[email-masked]>
Date: Wed, 18 Mar 1998 09:19:39 -0500

>admission control failure". 

This parameter was added so that an admission control module would have
some idea of how much layer-2 overhead would be associated with a flow.
The rate "r" only accounts for the IP part of the flow.  A pessimistic AC
module will assume that it has to add a layer-2 header every "m" bytes and
adjust its actual bandwidth reservation accordingly.

Therefore, if a flow tends to send small packets, more bandwidth is
necessary for the layer-2 headers, thus increasing the chance that the
reservation will fail.

-jj