International Business Machines Corporation

Thomas K Philips

Peter Anthony Franaszek

Gregory Michael Nordstrom

Christos J Georgiou

Martin W Sachs

Ting D Cheng

Thomas M Walker

Anujan Mangala Varma

Dynamic switch protocols are implemented on a token bus protocol in a shared medium network to improve the basic token bus functional capabilities and link utilization, and to produce a uniform transaction protocol that supports both token bus and dynamic switch networks. Frame formats common to both token bus and dynamic switch protocols are utilized, and circuit switched protocols are superimposed on a token bus protocol in interlocked and data transmissions to establish a circuit switched path between a token holder sender node and a destination node. An initial frame transmission uses a normal link header and establishes the circuit switched path between the sender node and the destination node. Subsequent data frames contain no link header information, thereby improving transmission efficiency, and the last frame in such a transmission disconnects the switched circuit path, thereby allowing other transmissions to resume. The use of circuit switched protocols within a token bus protocol allows more general transmission sequences and improves the utilization of token bus bandwidth.

Dynamic switch protocols on a shared medium network

A distributed algorithm for clock synchronization in address independent networks such as token rings and token busses is described. Synchronization is accomplished by using the fastest clock in the network as the master clock against which all other clocks in the network are synchronized. An algorithm is implemented in which each node sends out a message to all the other nodes in the network when its timer times out to tell its time. If a node receives a message with a higher clock time before it has had an opportunity to send out its own message, that node assumes that it is not the fastest node and it will not send out its message. Provision is made for maximum and minimum delays that are expected within a particular network. It has been proven that after a few cycles, all nodes will be synchronized to the node with the fastest clock and that this node will be the only one to transmit its time.

Clock synchronization algorithm for address independent networks

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Hopewell Junction, NY, United States of America

Thomas K Philips