Lookahead Network

This paper formalizes and extends a tree-based local area network, called the lookahead network, proposed by Lipovski, Goyal, and Malek. The leaf nodes in the network are workstations, and the nonleaf nodes consist of pure combinational logic used in carry lookahead circuits of binary adders. Any of the ring or bus access protocols (token passing, contention, etc.) can be used on this network. The first objective of this paper is to give a formal definition of the lookahead logic and show that it can be operated in either a bus or a ring mode. The advantage of using the lookahead logic is that it makes the network operation fail-soft, and since this logic is recursively defined, it simplifies network installation, expansion, and partitioning procedures. The second objective of this paper is to define a new round-robin access protocol on the lookahead network, which has much better throughputdelay characteristics than that of a token ring when the number of active nodes on the network is increased and/or the transmission speed is increased, and/or the average packet size is decreased. Moreover, this new protocol can implement a message-based priority scheme, which makes it useful in integrated voice and data networks.