Negotiation protocol for establishment of full duplex communication on a

Abstract

A technique for establishing and maintaining full duplex communication between two stations connected to a token ring network, without physically reconfiguring the station connections or otherwise disturbing the network. Each station continually performs a two node test to ascertain whether there are only two active stations on the network, and updates a two node flag that indicates whether or only two active stations are present. The two node test uses both upstream neighbor and downstream neighbor addresses to update the two node flag, and requires validation of either one of these addresses if the other one of them appears to have changed since the previous observation. A concurrently running full duplex control process uses the two node flag and other conditions to decide whether to initiate or continue transition to full duplex mode. The control process uses an exchange of full duplex request and acknowledgment frames and completes the transition to full duplex mode when each station has transmitted and received a Restricted Token.