1.1 Remote Access
1.1.1 WAN connection types
A WAN is a data communications network that covers a relatively broad geographic area, often using transmission facilities generally provided by service providers and telephone companies. Unlike LANs, a WAN connection is usually rented from the service provider. As shown in the Figure , WANs are used to connect various sites at different geographic regions so people at each site can exchange information.

The connection requirements vary considerably. For example, two sites may require a dedicated connection because they most often exchange real-time data. On the other hand, a mobile user may need to connect to a site only to periodically check e-mail throughout the day.

A network administrator building a remote network must weigh such issues as user needs, bandwidth requirements, and costs of the various technologies. The network administrator must then select the technologies that best suit the corporation’s needs and budget.

As illustrated in Figure , the variety of WAN connection types offered by service providers can be grouped into the following categories:

  • Dedicated connectivity (leased lines)
  • Circuit-switched networks
  • Packet-switched networks

Dedicated lines have point-to-point connections that are indefinitely reserved for transmissions, rather than being switched as transmission is required. Typically, a dedicated connection is made using serial lines. Circuit-switched connections are physical circuit paths that are only established during the duration of a call. Once the circuit is formed, all data travels the same path. Physical circuit-switched examples include asynchronous serial and Integrated Services Digital Network (ISDN). Packet-switched networks use packet-switching technology for data transfer. This means that the data is divided into separate packets. The packets include sequence numbers and a destination address. The packets can travel different paths and are reassembled at the destination. Frame Relay uses packet-switching technology.