tworking that we are now demanding from IP. In IP router-based networks, the core, like the core in the PSTN, is responsible for pro- viding interconnectivity. But in the IP router network, the core also provides server access and network management to the edge devices on the network periphery. Because of the increased traffic that networks are seeing today, the core net- work is becoming loaded, and that is resulting in increased latency and unaccept- able delays. At the edge of the LAN, a shortage of network capacity, coupled with proliferation of broadcasts and multicasts, can create significant network problems. However, those problems go away if the network is properly designed with VLANs that limit broadcast domains. When the edge demand exceeds the capacity of the core, queue overruns create capacity overload and lost packets, thereby reducing the availability and reliability of the network. As a result, users are suffering from congestion, inadequate server access, and slow response times. Traditional IP routers cannot deliver the service quality that is increasingly demanded. The shortcomings of traditional routers include poor path calculation and slow rerouting. Routers usually use the shortest-path metric to calculate their routes, so IP routers send traffic over a shorter path, even if it's congested, instead of over a more desirable, longer, or uncongested path. But this depends on the routing protocol used. RIP uses the shortest-path metric, whereas OSPF, EIGRP, and BGP allow for load balancing and do not always take the shortest path but instead take the "best" path, as defined by the administrator. This is one of the rea- sons that there is increased use of ATM or MPLS in the core for backbone traffic- engineering purposes. Also, in the event of a backbone circuit or router failure, IP routers can take a long time-up to a minute-to calculate the new paths around the failure. This has led to more reliance on the resilient SDH/SONET backbone infrastructure, where there is a backup path-a protect fi