# MEASUREMENT BASED OPTIMAL SOURCE SHAPING IN

##
Parijat Dube

### INRIA - Projet MISTRAL

### Résumé:

Integrated Services Packet Networks support a guaranteed
transport service (also called stream traffic) that is used
by applications that have an intrinsic (unmodifiable) temporal
behavior, and hence have tight end-to-end delay requirements
(e.g. real-time Variable Bit Rate (VBR) services).

Most on-line (i.e., not stored) VBR sources (like packet
telephony and motion compensated variable rate coded video)
would find it difficult to a priori declare the traffic
parameters required for a connection admission control strategy.
There is thus the problem of measurement based on-line
estimation of source parameters. In this talk we address the
problem of on-line estimation of OPTIMAL source parameters.
The parameters are OPTIMAL in the sense that they simultaneously:

1. Minimise a network resource(buffer at the switches + link
bandwidth) cost function.
2. Bound the shaping plus the multiplexing delay.

We provide a formulation for the characterisation of optimal
leaky bucket shaper parameters (since a source is invariably
shaped before feeding it into the network), i.e., the optimal
leaky bucket rate parameter (rho*) and the optimal leaky bucket
depth (sigma*). We then develop measurement based on-line
algorithms for estimating the opimal parameters, rho* and
sigma*. The algorithms are based on stochastic approximation
(continuous as well as discrete) techniques and can be implemented
at the source and/or the switch for on-line estimation of
OPTIMAL shaper parameters. Our approach yields significant
reduction in network cost by working with these on-line estimated
OPTIMAL parameters.
The research was supported by NORTEL NETWORKS, USA.