An intelligent, active hub that establishes, maintains, and changes logical connections over physical circuits. Switches flexibly connect transmitters and receivers across networks of interconnected ports and links, thereby allowing network resources to be shared by large numbers of end users. LAN switches are packet switches that can support multiple simultaneous transmissions, reading the destination address of each frame and forwarding it directly to the port associated with the target device. LAN switches are classified as workgroup switches or backbone switches.A workgroup switch serves the needs of a group of users who work together and, therefore, share common resources and intercommunicate frequently. Through the use of workgroup switches, a great deal of traffic can be confined to relatively small LAN segments and overall LAN congestion can be reduced considerably. High capacity backbone switches interconnect workgroup switches and provide connections to routers, as required. LAN switch architectures are several. A shared bus switch has a single high-speed bus that is shared by all incoming and outgoing ports on a time-division multiplexing (TDM) basis. A matrix switch contains multiple interconnected high-speed internal buses in a multi-bus switching matrix that can provide full bandwidth to multiple, simultaneous transmissions. If there are congestion issues in a matrix switch, it may have the ability to subdivide its capacity, with the buses becoming shared buses. A cut-through switch quickly reads the address of the data frame and quickly flows it through the switching matrix, bit by bit. A store-andforward switch temporarily buffers and examines each incoming frame for errors through a CRC check before forwarding it through the switching matrix to the output port. Fragment-free switching, is similar to cut-through except for the fact that the switch stores the first 64 octets of the frame before forwarding it.As most errors occur at the beginning of a frame, this approach eliminates the possibility that runt frames (i.e., truncated frames) will be transmitted.
A network device that cross-connects clients, servers and network devices. Also known as a "frame switch," stand-alone LAN switches are common in Ethernet networks. A four-port switch is also typically built into a wired or wireless router for homes and small business (see wireless router). LAN switches were available for Token Ring and FDDI networks, which have given way to Ethernet. ATM switches however are a type of LAN switch that is considered in a category by itself (see ATM). See Ethernet switch, Token Ring and FDDI.