Resilient Packet Ring (RPR) is an emerging standard for a packet basedring network. The MAC protocol defined by RPR is primarily intendedfor use in a metro (MAN) or wide area (WAN) environment, supportinglink capacities of multiple gigabits per second.
Being an IEEE 802 standard, RPR is required to support transparentbridging. Transparent bridging was originally designed for sharedmedium networks, like Ethernet. RPR is not such a shared mediumnetwork, hence some new problems are encountered.
Two different solutions for bridging in RPR are discussed in thiswork. The first, named basic bridging, is the one defined in theexisting draft standard. This bridging strategy relies heavily onbroadcasting on the rings, thus giving a poor utilisation of thenetwork resources. The second strategy, enhanced bridging, reduces andeventually eliminates this broadcasting. The price to pay is a needfor more memory in the stations on the ring to keep mapping tables.
A simulation model of RPR networks has been developed and used in thiswork to evaluate the performance of the two bridgingstrategies. Through three simulated network scenarios, differentaspects of the enhanced bridging algorithm are highlighted andcompared to the basic strategy.
This work shows that enhanced bridging at least halves the load on thenetwork produced by a bridged traffic flow compared to basic bridging.This is done by eliminating the need for broadcasting. Enhancedbridging depends on mapping tables in the RPR stations. Simulationsare performed that show the effect of limiting the size of thesetables. The last scenario shows how local traffic on a ring isaffected by the choice of bridging algorithm. The simulations showthat by reducing the traffic load in the network, the enhancedbridging algorithm gives improved latency and jitter characteristicsfor local traffic.