ABSTRACT
Layer 2 switches are increasingly mature and highly interoperable. This chapter provides an overview of the available technologies, and suggestions for features information technology personnel should examine when exploring the market for these products. Layer 3 switching is less mature. Layer 2 switching is essentially a bridging solution, with all of the implied scalability problems. Conventional routers have comparatively high latencies because all of the packet processing is done by central processing units that essentially form a bottleneck to traffic. The Layer 3 devices cooperate to route the first packet and discover the shortcut; the shortcut is then assigned a “tag” or “label” that is used by the Layer 2 switching function to speed subsequent packets on their way with no further involvement by the routing function. The evolution to Layer 3 switching is occurring in two sectors of the market. Manufacturers of local area network switches are integrating Internet Protocol and Internetwork Packet Exchange routing in their products.
