NETWORKING CONCENTRATORS

NETWORK DEVICES

HUB
A common connection point for devices in a network. Hubs are commonly used to connect segments of a LAN. A hub contains multiple ports. When a packet arrives at one port, it is copied to the other ports sothat all segments of the LAN can see all packets.

SWITCH
In networks, a device that filters and forwards packets between LAN segments. Switches operate at the data link layer (layer 2) and sometimes the network layer (layer 3) of the OSI Reference Model and therefore support any packet protocol. LANs that use switches to join segments are called switched LANs or, in the case of Ethernet networks, switched Ethernet LANs.

ROUTER
A device that connects any number of LANs. Routers use headers and a forwarding table to determine where packets go, and they use ICMP to communicate with each other and configure the best route between any two hosts. Very little filtering of data is done through routers. Routers do not care about the type of data they handle.

BRIDGE
A device that connects two local-area networks (LANs), or two segments of the same LAN. The two LANs being connected can be alike or dissimilar.
For example, a bridge can connect an Ethernet with a Token-Ring network.
Unlike routers, bridges are protocol -independent. They simply forward packets without analyzing and re-routing messages. Consequently, they're faster than routers, but also less versatile

REPEATER
A network device used to regenerate or replicate a signal. Repeaters are used in transmission systems to regenerate analog or digital signals distorted by transmission loss. Analog repeaters frequently can only amplify the signal while digital repeaters can reconstruct a signal to near its original quality. In a data network, a repeater can relay messages between sub networks that use different protocols or cable types. Hubs can operate as repeaters by relaying messages to all connected computers. A repeater cannot do the intelligent routing performed by bridges and routers.

MAU
MAU is short for Multistation Access Unit (also abbreviated as MSAU), a token-ring network device that physically connects network computers in a star topology while retaining the logical ring structure. One of the problems with the token-ring topology is that a single non-operating node can break the ring. The MAU solves this problem because it has the ability to short out non-operating nodes and maintain the ring structure. A MAU is a special type of hub.

CSU/DSU
CSU/DSU Short for Channel Service Unit/Data Service Unit. The CSU is a device that performs protective and diagnostic functions for a telecommunications line. The DSU is a device that connects a terminal to a digital line. Typically, the two devices are packaged as a single unit. You can think of it as a very high-powered and expensive modem. Such a device is required for both ends of a T-1 or T-3 connection, and the units at both ends must be set to the same communications standard.