Gamma on Dec 2114x with Eecient Flow Control

GAMMA is a prototype lightweight communication system based on the Active Ports paradigm, designed for eecient implementation over Fast Ethernet interconnects. The original implementation started in 1996 based on 3Com 3C595 cards. The optimizations obtained on that NICs allowed us to obtain the lowest latency and highest throughput results ever published in the literature for Fast Ethernet. Technology evolved, however, and now all low-cost NICs available are based on Descriptor Based DMA (DBDMA) transfers, originally introduced by the DEC chipset 21140. In this paper we report on the re-implementation of the GAMMA prototype for the DEC NICs exploiting the new transfer modes and achieving substantially equivalent performance gures. We also describe the addition of an eecient ow-control algorithm, that allows loss-free communications without seriously aaecting performance.