A Word Regarding Remote Access

While many of the technologies that we discussed in this chapter are related to expanding LANs beyond a particular geographical location, some of the technologies such as modems, ISDN lines, and DSL connections are also commonly used by remote users to connect to the corporate LAN. Not every company or businessespecially small businesses and home officeswill make use of WAN technology to expand the range of their LAN. However, even the smallest of businesses (including a home business) might need to allow users to dial in to the local area network and access resources on the LAN as if they were directly connected to the network.

For remote access to work, both the remote user and a special server on the LAN, called a remote access server , must be outfitted with some sort of WAN communication strategy. And while modems have been commonly used on both remote access client computers and on remote access servers on the LAN, other technologiessuch as ISDN and even X.25 connectionscan be used.

Remote access servers that handle numerous dial-in connections are often outfitted with multiple phone lines and multiple modems. A collection of modems on a remote access server is called a modem pool .

While expanding the LAN through remote access must certainly be considered a deployment of WAN connectivity, the use of dial-up connections certainly isn't as glamorous as many the WAN technologies that we have discussed in this chapter, such as the T-Carrier system and ATM. However, managing remote access is an important aspect of being a network administrator. We will discuss setting up remote access servers and remote access clients in Chapter 17.

The Absolute Minimum

In this chapter we had an opportunity to take a look at the different WAN technologies used to connect LANs at different locations. Some of these technologiessuch as modems, ISDN, and DSL connectionsare also used by users who connect to the network remotely.

• The POTS (Plain Old Telephone System) provides a number of different strategies for WAN connectivity.

• Dial-up connections over regular analog phone lines using modems provide a relatively inexpensive method of expanding a LAN.

• Asynchronous modems move data over regular phone lines. Synchronous modems are often used on leased digital lines to provide WAN connectivity.

• The T-Carrier system provides high-speed digital lines that can transfer voice, video, and data.

• ISDN and DSL are WAN technologies that allow for the transfer of data on regular phone lines.

• Frame Relay and ATM are both packet-switching WAN technologies that provide for the high-speed movement of data over switched networks.