LAN Expansion

Networks cannot be made larger by simply adding new computers and more cable because each topology has its limits. However, there are certain components which can increase the size of the network within the existing environment. These components are:

• Repeaters
• Routers
• Bridges
• Brouters
• Gateways

Repeaters

A Repeater is a device that regenerates signals so that the signal can travel on additional cable segments. They do not translate or filter data. For a repeater to work, both segments that the repeater joins must have the same media access scheme, protocol and transmission technique.

Repeaters can move packets from one medium to another. Some multiport repeaters can connect different types of media. Repeaters improve performance by dividing the network into segments, thus reducing the number of computers per segment.

Routers

A Router is a device used to connect networks that use different architectures and protocols. They can switch and transfer information packets across multiple networks. This process is called routing. They can determine the best path for sending data and filtering broadcast traffic to the local segment. Routers cannot link to remote computers. They only read addressed network packets. Routers can link segments that use different data packaging and media access schemes.

Bridges

A Bridge is a device that can join two LANs. However, a bridge can also divide an overloaded network into separate networks, reducing the traffic on each segment and making each network more efficient. A bridge can link unlike physical media such as twisted-pair and coaxial Ethernet. It can also link unlike network segments such as Ethernet and Token Ring.

They are also referred to as Media Access Control layer bridges. A Media Access Control layer bridge:

• Checks the source and destination address of each packet.
• Creates a routing table.
• Forwards packets.

Note: A routing table stores the addresses and all the other information necessary to route information from one network to another.

If the destination address is not listed in the routing table, the bridge forwards the packets to all segments.

Multiple bridges can be used to combine several small networks into one large network. A bridge can be installed internally or externally. Bridges are faster than routers because routers perform complex functions on each packet.

The following are the differences between bridges and routers:

• The bridge only recognizes the addresses of network cards in its own segment. Routers recognize network addresses.
• A bridge can only recognize one path between networks. A router can search among multiple active paths and determine the best path.
• The router only works with routable protocols.

Brouters

A Brouter combines the best features of both a bridge and a router. Brouters can:

• Route routable protocols.
• Bridge non-routable protocols.

Gateways

Gateways make communication possible between systems that use different communication protocols, data formatting structures, languages and architectures. Gateways repackage data going from one system to another. Gateways are usually dedicated servers on a network and are task-specific.