LAN hardware includes the actual cabling and the infrastructure – the internetwork connections. Servers must be able to access other servers and users must be able to access information anywhere in the network. In client/server environments, servers send fewer packets per request than in other environments because only the results of requests are send back to the client. However, this may not ultimately decrease network traffic because client/server environments usually support more users than mainframe-oriented network.
There are five ways to interconnect Local Area Networks:
1. Repeaters
2. Bridges
3. Routers
4. Network hardware gateways
5. Backbone networks
The methods are listed in order of increasing functionality. Backbone networks are connecting networks; they are not pieces of hardware that connect networks.
Repeaters:
As a signal travels along a cable, it loses strength. If communicating stations are at great distances from one another, repeaters can be used to regenerate the signal back to its original strength. A repeater can also be used to extend the reach of a LAN. Repeaters can only be used when the Local Area Networks on both sides of the repeater are identical. They must have the same physical transmission characteristics and use the same protocols.
Bridges:
Bridges are used to connect Networks with different physical transmission characteristics and protocols. For example, a third-party bridge might be used to link multiple Ethernet Local Area Networks, each supplied by different manufacturers. Bridges are a simpler technology than routers. They operate at the Media Access Control sub layer of the Data Link Layer of the OSI model.
Routers:
A router is a hardware device that manages the route selection for data packets and for minimizing traffic loads on linked Networks. Router link logically separate Networks, permitting them to share traffic loads and prevent the choking that occurs in bridged Networks.
Routers are used to connect two different networks. Each network may have been implemented independently and include stations with the same address. Router performance is typically rated by the same two variables as bridges: filtering rate and forwarding rate, both measured in packets or frames per second.
Network Hardware Gateways:
Networks gateways are used to connect networks that are entirely different. Network gateways perform all the conversions necessary to go from one set of protocols to another, including:
1. Message Format Conversion.
2. Address Translation.
3. Protocol Conversion.
Backbone Networks:
Many organizations are now providing connections between Local Area Networks using backbone networks. Backbone networks are of a higher quality than the connected Networks and usually use microwave-based links.
The methods are listed in order of increasing functionality. The characteristics of the Local Area Networks to
be connected determine which device should be used.
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