PARTIAL-ORDER TRANSPORT SERVICE FOR MULTIMEDIA AND OTHER APPLICATIONS

This paper investigates a partial-order connection (POC) service/proto col. Unlike classic transport services that deliver objects either in the exact order transmitted or according to no particular order, POC p rovides a partial-order service; that is, a service that requires some , but not all objects to be received in the order transmitted. Two ver sions of POC are proposed: reliable, which requires that all transmitt ed objects are eventually delivered, and unreliable, which permits the service to lose a subset of the objects. In the unreliable version, o bjects are more finely categorized into one of three reliability class es depending on their temporal value. Two metrics based on e(i)(P), th e number of linear extensions of partial-order P in the presence of i lost objects, are proposed as complexity measures of different combina tions of partial order and reliability. Formulae for calculating e(i)( P) are derived when P is series-parallel. A formal specification of a POC protocol, written in Estelle, is presented and discussed. This spe cification was designed and validated using formal description tools a nd will provide a basis for future implementations.