A local area network (LAN) (Figure 8-3) is a small area networked with a series of cables or wireless access points that allow computers to share information and devices on the same network. LANs are the least expensive to install, and they are much faster than WANs because of their smaller size. A LAN has the fastest communication technology because less equipment and fewer resources are needed to complete the network. Generally the larger networks are composed of several LANs interconnected to create the WAN. The picture archiving and communication system (PACS) workstations in a radiology reading room would be considered a LAN. The computers are interconnected and communicate by sharing images and reports.

A wide area network (WAN) is a network that spans a large area: city, state, nation, continent, or the world (Figure 8-4) It is used to connect computers that are not physically attached through conventional network cables but are rather connected through other means, such as telephone lines, satellite links, or other types of communication cable. The use of these long distance communication links drives up the operating costs of this type of network because most often these communication links are owned by a separate company, and because of the distance covered, the cost of having the highest speed equipment is expensive.

In a peer-to-peer network (Figure 8-5), each computer on the network is considered equal; no computer has ultimate control over another. Each computer controls its own information and operation and can function either as a client or as a server depending on the needs of the other computers on the network. The peer-to-peer network is the most popular small office or home network configuration because it is the least expensive and most simple to set up. However, a peer-to-peer network has a limited scope because the maximum number of peers that should be connected is 10. More than 10 peers causes bottlenecks and collisions on the network. An example of a peer-to-peer network is a small medical office with several computers connected to check in patients, verify insurance, produce bills for the service, and document patient history. A printer is shared among the group of computers.

In a server-based network (Figure 8-6), there is a centralized computer (the server) that controls the operations, files, and sometimes the programs of the computers (the clients) attached to the network. The server provides a location for centralized storage and retrieval on the network. This allows the users to move from computer to computer and access their files from a central location. When a client requests a file, the server sends the entire file to the client for processing. Once the processing is completed, the client sends the entire changed file back to the server for storage. This type of network requires that the server be of high quality and high capacity, although the client computers can be less expensive.

There can be multiple servers on this type of network, but there must be one dedicated server that controls the network. An example of this type of network is a radiology department using a PACS to read and distribute images throughout the hospital. Computers throughout the hospital are connected to the centralized server that contains all of the images, and the images are sent out to the computers as requested.