Subject: GSn: a new type of service for integrated services on the Internet

From: Francesco Potorti` <[email-masked]>
Date: Tue, 16 Jun 1998 18:58:09 +0200 (CEST)

Hi,

I would like to receive comments on a  new service type we devised for
integrated services, which is a  straightforward extension to GS.  The
full paper, which is being submitted for publication, can be retrieved
in Postscript format at ftp://fly.cnuce.cnr.it/pub/GSn.ps{,.gz,.bz2}.

The paper assumes a situation  which is typical of video-on-demand:  a
single server  and multiple receivers,  where the server can compute a
completely precise characterization of  the traffic, and the receivers
have different delay bounds for the reception of packets.

We assume that  the receivers do not  change  the server's Tspec,  and
that each receiver computes its Rspec from the Tspec and its desidered
delay bond.  In this situation, the server could  make the best use of
the available  bandwidth  if it knew  in  advance the receivers' delay
bounds.  In particular, for a given traffic envelope and a given delay
bound, it is possible to compute  a token bucket  (b,r) such that R is
minimal.  However,  the delay bounds are  generally different for each
receiver, and the server does not generally know them in advance.

So we propose to generalise  the (b,r) token bucket  used in GS to  an
array of  n token buckets  (GSn).  When n=1,  GSn behaves exactly like
GS.  When n>1, the server  includes n token  buckets in the Tspec, and
each receiver, knowing its  delay bound, computes  R relative to  each
token bucket.  It then includes the n resulting R's in its Rspec.

The way Rspec's are merged is similar to GS, that is,  for each row of
the array,  the  maximum R is  chosen.   At  each  router's downstream
interface, traffic control is performed using  the single token bucket
whose corresponding  R is  minimal.   This policy  guarantees that the
minimum possible  R  is used at  each  traffic control   module, while
maintaining traffic control complexity the same as in GS.

Thanks for having the patience of reading so far :-)

-- 
Francesco Potorti` (researcher)        Voice:    +39-50-593 203 (op. 211)
Computer Networks Group                Fax:      +39-50-904052
CNUCE-CNR, Via Santa Maria 36          Email:    [email-masked]
56126 Pisa - Italy                     Web:	 http://fly.cnuce.cnr.it/