The paper compares and contrasts various methods presently available for specification, validation and verification, with emphasis on verification. We describe an application of formal methods to protocol specification, validation, and verification, using an actual protocol as an example. We use a process algebra to build models of an OSI protocol and test these models using a model checker. Model checking allows us to verify large and complex models and use formal methods as practical solutions. We also show an example with an automated theorem prover.

The authors present an all-optical hypercube-based multichannel network, implemented on a ring topology, using wavelength division multiplexed channels. For a network of size N, only log/sub 2/N distinct channels are required. They design an optical network interface unit (ONIU), which employs free-space optics to perform routing and switching functions. The design eliminates the electronic bottleneck at intermediate nodes and is capable of performing high speed packet switching. ONIU can be reconfigured in the GHz range and provides the high bandwidth necessary to perform distributed and parallel computing in a local area network environment.>

A distributed computer system based on a hypercube topology is proposed, where multiaccess channels spanning all dimensional axes provide processor interconnection. The multiprocessor system can be built at relatively low cost by combining the recent advances in high-capacity channels available through fiber optics, and demand-assignment multiple-access protocols, creating a highly fault-tolerant system with good average packet delay and average distance characteristics, at a significantly reduced cost. A totally distributed system has been achieved in which the packets are self-routing, able to take advantage of the multiple paths of equal length between two modes. The proposed structure gives a highly fault tolerant system, degrading gracefully in the presence of failures.>

An approach to local area network interconnection is presented Which combines the advances in static interconnection topologies, demand assignment multiple access protocols, and the availability of high-bandwidth fiber optic channels to create a cost-effective structure capable of interconnecting a large number of LAN's with heavy traffic. This approach is independent of the protocol implemented at each LAN. The structure is based on a hypercube topology where each vertex of the graph represents a LAN. Multiple access channels spanning all dimensional axes are used in this scheme. This approach is compared to a topology with direct point-to-point connections between all nodes sharing a common axis. Through the development of the degree, diameter, average distance, cost, and average packet delay, we show that using fewer high-capacity channels, a LAN interconnection network with excellent performance characteristics can be constructed, able to support a large number of LAN's with heavy traffic at a significant reduction in cost over the point-to-point case. The resulting structure has many of the desirable characteristics for static interconnection networks such as high fault tolerance, totally distributed packet routing in the interconnection network, low average distance for good performance, and low degree, resulting in low cost. For the total number of required LAN nodes and the expected amount of internode traffic, the structure is optimized for minimum cost.

A sampling of routing algorithms is evaluated through simulation. The algorithms selected are random walk, fixed directory, split traffic, isolated shortest queue (hot potato) and backward learning. Backward learning exhibited the most desirable characteristics, approaching fixed directory routing in delay and path length, while adapting to link failures.

The paper describes the real-time implementation of a telephone channel simulator on the TMS32010 digital signal processor. Several characteristics are simulated, including harmonic distortion, attenuation distortion, group delay distortion, listener echo, frequency offset, phase jitter, gaussian noise, impulsive noise, phase jumps and gain hits. A design program written in Pascal and running on a personal computer allows the user to specify and test a channel response, then generate the TMS32010 code for the real-time implementation.