Internetworking Devices : Repeaters, Hubs, Bridges, Switches, Router, Gateway

Repeater

A repeater is the physical layer devices which are used to regenerate the signal between similar networks. It extends the distance over which a signal may travel down a cable. A repeater is a low-cost device.

Hub

Hub, also called the multiport repeater is a physical layer device. It functions similar to the repeater. In a Hub, the signal received at the one port is transmitted to all the other ports and vice-versa.

Advantage : Hub is low-cost device and easy integration.

Disadvantage : It reduces the bandwidth.

Bridge

Bridge is a data link layer devices. It functions very similar to a switch, sometimes also called the two port switch. It maintains MAC table with MAC address and the port no. and decides whether to forward the frame or not. Bridge divide the network into different LAN Segment.

Switches

A switch is also called the multiport bridge. It is a data link layer devices. The switch is a hub with some intelligence. It doesn't distribute the signal without verifying whether the signal needs to propagate to given port. The decision is based on the internal configuration. A switch dynamically builds and maintains a MAC table, which holds all the necessary information for each port.

Router

A router is a special type of computer which connects multiple networks and uses routing to forward packets. Router works at Network Layer of OSI reference model. It maintains the routing table to route packet to the destination address. Because it is expensive and slower there is a popular statement "Use switch where you can Use router where you must".

Gateway

Gateway is a server that appears to the client as if it were an origin server. It is the most complex devices with respect to the functionality. A Gateway is used to connect two different environments such as a Frame-Relay network and an X.25 network.

References:

1. A.S. Tanenbaum, “Computer Networks”, 3rd Edition, Prentice Hall India, 1997.
2. W. Stallings, “Data and Computer Communication”, Macmillan Press, 1989.
3. Kurose Ross, “Computer Networking: A top-down approach”, 2nd Edition, Pearson Education
4. Larry L. Peterson, Bruce S. Davie, “Computer Networks: A Systems Approach”, 3rd Edition, Morgan Kaufmann Publishers