Lesson 6: WAN Basics

WAN Basics | Transmission Options | WAN Requirements & Solutions

How to choose Service?

Analog services are the least expensive type of service. ISDN costs somewhat more but improves performance over even the fastest current analog offerings. Leased lines are the costliest of these three options, but offer dedicated, digital service for more demanding situations. Which is right?
You’ll need to answer a few questions:

 - Will employees use the Internet frequently?
 - Will the Internet be used for conducting business (for example, inventory management, online    catalog selling or account information or bidding on new jobs)?
 - Do you anticipate a large volume of traffic between branch offices of the business?
 - Is there a plan to use videoconferencing or video training between locations?
 - Who will use the main office’s connection to the Internet - individual employees at the central    office, telecommuting workers dialing in from home, mobile workers dialing in from the road?

The more times the answer is “yes”, the more likely that leased line services are required. It is also possible to mix and match services. For example, small branch offices or individual employees dialing in from home might connect to the central office using ISDN, while the main connection from the central office to the Internet can be a T1.
Which service you select also depends on what the Internet Service Provider (is using. If the ISP’s maximum line speed is 128K, as with ISDN, it wouldn’t make sense to connect to that ISP with a T1 service. It is important to understand that as the bandwidth increases, so do the charges, both from the ISP and the phone company. Keep in mind that rates for different kinds of connections vary from location to location.

Let’s compare our technology options, assuming all services are available in our region. To summarize:

 - A leased-line service provides a dedicated connection with a fixed bandwidth at a flat rate. You pay the    same monthly fee regardless how much or how little you use the connection.

 - A packet-switched service typically provides a permanent connection with specific, guaranteed bandwidth    (Frame Relay). Temporary connections (such as X.25) may also be available. The cost of the line is typically    a flat rate, plus an additional charge based on actual usage.

 - A circuit-switched service provides a temporary connection with variable bandwidth, with cost primarily    based on actual usage.