Layer 4 switches, operating at the Transport layer, allow network managers to choose the best method of communicating for each switching application. Unless their algorithms and processor support high speeds, though, these switches are slower.
They incorporate routing functions to actively calculate the best way to get a packet to its destination.
These switches are smarter than Layer 2 switches. Layer 3 switches use network or IP addresses to identify locations on the network, identifying the network location as well as the physical device. Layer 3 switches use routing protocols such as RIP or OSPF to calculate routes and build their own routing tables. These network backup units are usually designed specifically to provide high levels of automation, intelligence, and security. Layer 3 switches, operating at the Network layer, are designed for disaster recovery service (or, more importantly, for disaster avoidance). They only look at the data packet to find out where it’s headed. These switches will be fast but not terribly smart. These switches operate using physical network, or MAC, addresses. By monitoring control and data events, these switches automatically reroute circuits or switch to backup equipment, as the need requires. Layer 2 switches, operating at the Data Link layer, can be programmed to respond automatically to a wide range of circuit conditions. Thus, their main difference from bridges is typically the technology used to implement frame forwarding, which is mostly hardware-based, in contrast to typical bridges, which generally are more programmable and accommodate a wider range of heterogeneous LANs.įigure 4.22. However, due to their focus on performance for dedicated segments, they employ specialized hardware for frame forwarding, and some of them even employ cut-through routing techniques instead of the typical store-and-forward technique used in common bridges. For example, with an Ethernet switch and a dedicated Ethernet segment per attached system, collisions are avoided and delay is minimized.Ĭonsidering the need for autonomous operation and high performance, layer 2 switches perform all operations that typical bridges do. The original goal of these switches was to enable use of a single LAN segment, if feasible, per attached end system, minimizing contention delays that existed in the older shared segments. As structured cabling emerged and star-based connectivity to network centers was adopted, the exploitation of existing cabling and existing network adapters led to the continuation of using typical LANs, such as Ethernet and Token Ring, but enabled the development of layer 2 switches. Historically, layer 2 switches emerged to alleviate the contention problem of shared media LANs. They interconnect networks at layer 2, most commonly at the MAC sublayer, and operate as bridges, building tables for the transfer of frames among networks. Dimitrios Serpanos, Tilman Wolf, in Architecture of Network Systems, 2011 Layer 2 switches
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