Ethernet units adapted for loop configuration and method of operating same

摘要

A packet-switched network system comprises a multiplicity of multi-port network units each of which has first and second ports and other ports and transmission links coupling the first and second ports of said unit in a closed ring. The first and second ports and transmission links support duplex transmission of Ethernet data packets. Each unit transmits from said first and second ports packets including selected information enabling on reception of a packet at any of the units a determination of a number of hops from unit to unit around said ring said packet has made. Each unit has a forwarding database and in response to the said selected information controls the transmission of said packets in two directions around said ring, and each unit causes discard of packets which have according to said selected information circumnavigated the ring.