Chapter 6. Modems and Asynchronous Connections

Terms you'll need to understand:

• Data Terminal Equipment (DTE) and Data Communications Equipment (DCE)

• Recommend Standard (RS)-232 and Electronic Industries Association/Telecommunications Industry Association (EIA/TIA)-232-C

• Request to Send (RTS), Clear to Send (CTS), Data Terminal Ready (DTR), Carrier Detect (CD), and Data Set Ready (DSR)

• Pulse code modulation (PCM) encoding

• Error detection and correction

• Compression

• Reverse Telnet

• Autoconfiguration

• Modemcap database

Techniques you'll need to master:

• Configuring an asynchronous line

• Selecting cables and adapters

• Setting up modem autoconfiguration

• Configuring modems manually

• Maintaining the modemcap database

• Debugging modem autoconfiguration

Asynchronous connections via modem have and will continue to be an integral part of any wide-area network (WAN) implementation. Although it has been relegated to "backup" status in most cases, the asynchronous connection still has many things going for it, not the least of which are its ready availability and low cost.

Regardless of the nature of the asynchronous connection you are using, you need to be able to correctly choose and deploy the proper cabling and master the configuration of the router, its resources, and modems attached to the router. Cisco and the computer industry as a whole have done an admirable job of streamlining and simplifying this process.