Compare and contrast the following WAN devices: modem, CSU/DSU, access server, WAN switch, and router.

Compare and contrast the following WAN devices: modem, CSU/DSU, access server, WAN switch, and router.

Modem:

• A voiceband modem converts and reconverts the digital signals produced by a computer into voice frequencies that can be transmitted over the analog lines of the public telephone network.
• Faster modems, such as cable modems and DSL modems, transmit using higher broadband frequencies.

CSU/DSU:

• Digital lines, such as T1 or T3 carrier lines, require a channel service unit (CSU) and a data service unit (DSU).
• The two are often combined into a single piece of equipment called the CSU/DSU.
• The CSU provides termination for the digital signal and ensures connection integrity through error correction and line monitoring. The DSU converts the T-carrier line frames into frames that the LAN can interpret.

Access server:

• Concentrates dial-in and dial-out user communications. It may have a mixture of analog and digital interfaces and support hundreds of simultaneous users.

WAN switch:

• A multiport internetworking device used in carrier networks to support Frame Relay, ATM, or X.25.

Router:

• Provides internetworking and WAN access interface ports that are used to connect to the service provider network.
• These interfaces may be serial connections or other WAN interfaces. They may require an external device such as a DSU/CSU or modem (analog, cable, or DSL) to connect to the service provider.

Exam with this question: EWAN v4 Chapter 1 Check Your Understanding: Introduction to WANs