Hub

The point on a network where circuits are connected. In local area networks, a hub is the core of a physical star configuration, as in ARCNET, StarLAN, Ethernet, and Token Ring. Hub hardware can be either active or passive. Wiring hubs are useful for their centralized management capabilities and for their ability to isolate nodes from disruption. Hubs work at Layer 1 (Physical) and 2 (Data Link) of the OSI Reference Model, with emphasis on Layer 1. Hubs aren't switches, as they have very little intelligence, if any, and don't set up transmission paths. Rather, hubs comprise a physical bus and numerous ports, to which are connected a bunch of wires, to which are connected individual terminal devices. As hubs are protocol-specific (e.g, Ethernet) and are not intelligent, they are very fast and very cheap. A 10Base-T hub is an inexpensive means of allowing LAN-attached devices to share a common, collapsed bus contained within a hub chassis. The connections are via UTP (Unshielded Twisted Pair), which is much less expensive than are the classic connections through coaxial cable. Unlike switches, hubs do nothing internally to control congestion. However, they typically are workgroup-level solutions which allow a large, logical Ethernet to be subdivided into multiple physical segments. For example, you could even use a small five-port hub on your desk to connect a couple of laptops and a desktop PC. Hubs can be interconnected directly, or through switches or routers, with the traffic being forwarded from the originating hub only if the destination address of the data packet indicates that is necessary to do so. Therefore, hubs do reduce congestion through the control of interhub traffic.