Evaluating the impact of ALF on communication subsystems design and performance

The lack of exibility and eeciency of the traditional layered model has led researchers to consider new approaches when designing communication subsystems. In particular, one approach consists of implementing protocol subsystems tailored to application requirements. The Application Level Framing concept in which the communication subsystem is able to process data in chunks of application-speciic size illustrates such adaptative and integrated approach. In this paper we discuss the impact of the ALF approach on both the design and the performance of the communication subsystems. Speciically, we examine the eeects of ALF on the implementation of a server for digital images. We nd that performance can be increased when using the ALF concept and that applications can beneet from the out-of-order processing. We multiply by two the throughput when applying ALF over Internet instead of TCP/IP. We show also that the choice of the Application Data Unit size is an important issue for performance.