Research Seminar - August 18, 2000

Abstract

The IETF Differentiated Services (diffserv or DS) Working Group has recently defined a Per Hop Behavior (PHB) called Expedited Forwarding (EF) intended for use in building a scalable edge-to-edge service that appears to the end points like an un-shared, point-to-point connection or a dedicated wire. The set of specifications necessary on the aggregate traffic (in DS terminology, a Per Domain Behavior or PDB) in order to meet these requirements defines a new PDB, the ‘Virtual Wire’ PDB of some fixed capacity.

In this presentation, we summarize a formal model for the PDB by explicitly identifying key timing and decision variables and associated design parameters. We look at the necessary and sufficient conditions for creating and establishing a Virtual Wire flow. We outline methods for quantifying design parameters and setting decision parameters and discuss their extensions to incorporate variations in traffic characteristics.

The study provides a synthesis of various methods in delivering a particular but versatile solution. The issue of scalability, the edge-to-edge service characteristics and a simple management of DS-domain provide the basis for the presented solution.