© 2005 Cisco Systems, Inc. All rights reserved.INTRO v Module Summary A WAN allows the transmission of data across broad geographic distances. There are a number of technologies involved in the functions of WANs, including hardware devices, such as routers, communication servers, and modems, and software functions. A common type of WAN connection is the point-to-point connection, which is also referred to as a serial or leased-line connection because the lines are leased from a carrier (usually a telephone company) and are dedicated for use by the company leasing the lines. Circuit switching allows multiple sites to connect to the switched network of a carrier and communicate with each other. This technology provides a more cost-effective means of WAN connection and includes its own set of technologies, including the PSTN and ISDN. As a means of increasing the efficiency and reducing the cost of WAN communication links, packet switching provides a technology that carries data differently from circuit-switched environments and uses protocols and technologies, such as X.25, Frame Relay, DSL, and ATM.

© 2005 Cisco Systems, Inc. All rights reserved.INTRO v2.17-2