3Com OfficeConnect Remote 510 User Manual

Contents

A-6 BRIDGING AND ROUTINGNetwork TopologyIf your network topology is star shaped, acombination of ISDN and bridging is usually themost efficient and successful option. Routing is abetter solution if your network topology is a complexmix of both leased line and ISDN circuits, running at64 Kbps to 2 Mbps.Broadcast StormsBridges are programmed to automatically forwarddata packets by default while routers filter datapackets by default. These attributes have an impacton the overall flow of data across the network. Muchhas been made of broadcast storms in connectionwith bridged networks, where the broadcast signalsfrom bridges propagate to fill all of the wide areabandwidth, and bring the network down. Broadcaststorms cannot be attributed to installation ofbridges or routers, but by poor protocolimplementation and network design. However thedeployment of routers can effectively firewall onelogical network from another.Optimum Use of ResourceBridged networks use Spanning Tree Protocol (STP)to provide network resilience, by retaining redundantlinks on stand-by, in case the primary link fails. Thismeans that you are not making maximum use ofavailable resources.Routing protocols make each node aware of theprimary and alternate routes available, ensuring thatresources (particularly WAN links) are not wasted.Routers have been designed to provide the optimumroute through the network from the workstationthrough to the destination resource with which theuser wishes to communicate. In a very large networkthere could be multiple paths available, and thesecould change as dedicated links go in or out ofservice. These changes in network topology arehandled by routing protocols. However, when usingthe ISDN the source network can dial direct to thedestination network, and establish a point-to-pointbridged or routed connection. Generally, whenusing this type of ISDN dial-up link, routing does notprovide much extra benefit.Rc.bk : RCAPPA.FRM Page 6 Thursday, July 10, 1997 9:53 AM