Virginia 23529 / Photonics and Other Approaches to High Speed

Coarse-grain parallelism in networking (that is, the use of multiple protocol processors running replicated software sending over several physical channels) can be used to provide gigabit communications for a single application. Since parallel network performance is highly dependent on real issues' such as hardware properties (e.g., memory speeds and cache hit rates), operating system overhead (e.g., interrupt handling), and protocol performance (e.g. effect of timeouts) we have performed detailed simulation studies of both a bus-based multiprocessor workstation node (based on the Sun Galaxy MP multiprocessor) and a distributed-memory parallel computer node (based on the Touchstone DELTA) to evaluate the behavior of coarse-grain parallelism. Our results indicate: /I) (Soarse-grain parallelism can deliver multiple lOOMbps with currently available hardware platforms and existing networking protocols (such as TCP/IP and parallel FDDI rings)? |2) ^Scale-up is near linear,in,ji, the number of protocol processors and channels (for small n and upto a few hundred Mbps)!<(|3) .Since these results are based on existing hardware without specialized devices (except perhaps for some simple modifications of the FDDI boards), this is a low cost solution to providing multiple lOOMbps on current machines. In addition, from both the performance analysis and the properties of these architectures, we conclude: , ' l) Multiple processors providing identical services and the use of space division multiplexing for the physical channels can provide better reliability than monolithic approaches^;!!' also provides graceful degradation and low-cost load balancing^) .Coarse-grain parallelism supports running several transport protocols in parallel to provide differenttypes of service^-For example, one TCP handles small messages for many users, other TCPs running in parallel provide high bandwidth service to a single application^ ' (3) ^Coarse grain parallelism will be able to incorporate many future improvements from related (e.g., reduced data movement, fast TCP,.fine-grain parallelism) also with a near linear speed-ups.