Networks and Communication Department

NET 324 D

Lec1 : Network Devices

1

Hubs and Repeaters

Typical LAN devices include repeaters, hubs, bridges, switches, and routers.

A repeater receives the signal, regenerates it, and passes it on.

Repeaters are used mainly at the edges of networks to extend the wire so more workstations can be added.

Hubs and Repeaters

Using a hub changes the network topology from a linear bus, where each device plugs directly into the wire, to a star.

Data arriving over the cables to a hub port is electrically repeated on all the other ports connected to the same Ethernet LAN, except for the port on which the data was received.

Hubs come in three basic types: Passive Active Intelligent

Bridges and Switches Bridges and switches operate at

the data link layer of the OSI model.

The function of the bridge is to make intelligent decisions about whether or not to pass signals on to the next segment of a network.

When a bridge sees a frame on the network, it looks at the destination MAC address and compares it to the forwarding table to determine whether to filter, flood, or copy the frame onto another segment.

Bridges and Switches

Switches learn certain information about the data packets that they receive from computers on the network.

They use this to build forwarding tables to determine the destination of data being sent by one computer to another on the network.

They help segment a network and reduce network traffic congestion by limiting each port to its own collision domain.

RoutersRouters operate at the Network

layer of the OSI model. They are slower than bridges

and switches but make "smart" decisions on how to route packets received on one port to a network on another port.

Routers are capable of segmenting the network.

Routers are capable of segmenting a network into multiple collision domains as well as into multiple broadcast domains.

Routers

Routers can be computers with special network software installed on them or they can be other devices built by network equipment manufacturers.

Routers contain tables of network addresses along with optimal destination routes to other networks.