There are two approaches to adaptive routing protocols for wide-area store-and-forward networks: dista,ncevector and link-state.

We compare the performance of two recently proposed distance-vector algorithms (Merlin-Segall and Extended Bellman-Ford) with a link-state algorithm (SPF), under varying file transfer workload. (Unlike the traditional distance-vector algorithms, these new distance-vector algorithms do not suffer from long-lived loops.) Our comparison is done using a recently developed network simulator. MaRS. We consider both dynamic and static file transfer connections, and both uniform and hotspot distributions of source-sink pairs. Our conclusion is that Extended Bellman-Ford performs as well as SPF in terms of delay and throughput. This suggests that distance-vector algorithms are appropriate for very large wide-area networks, since their space requirements are less than that of link-state algorithms.

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In this paper we introduce a new type of combined SIMD/MIMD architecture called a hybrid system. A hybrid system consists of two components. The first component is massively parallel and consists of a large number of slow processors that are organized in an SIMD architecture. The second component consists of only a f e w fast processors (possibly only one) which are organized in an MIMD architecture. W e contend that a hybrid system provides a means to adequately adjust t o the characteristics of a parallel program, i.e. changing parallelism. W e describe the machine and application model, and discuss the performance impact of such a system.Viewing the CM-2 with its front-end as a special case of a hybrid system, we substantiate our arguments and report measurements f o r a Gaussian Elimination Algorithm.

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