• maximize bandwidth efficiency
• minimize the costs to attain particular levels of performance
• prepare for the future

Obviously, there are a lot of other issues to be considered.  But these are likely to be the overarching objectives.

Now we present a review of the available WAN technologies along with relevant links to earlier web pages.  We will follow Teare's approach with some additions and rearrangement.

Analog Modems.  Analog modems operate over PSTN - Public Switched Telephone Networks primarily to

• connect telecommuters and mobile users who access the network for fewer than a couple hours each day
• provide backup for other types of links

The following link for dial-up service provides some additional perspective.

Leased Lines.  Leased lines are used primarily to provide

• connectivity in point-to-point networks and hub-spoke topologies
• backup for other types of links

There are a very large variety of options for leased lines such as DSL, T1/T3, and others.  Within these you could also make use of VPN.

ISDN.  ISDN - Integrated Digital Services Network is one of the higher quality connection alternatives that is generally used to provide

• cost effective remote access to corporate networks for telecommuters and remote offices
• support for voice and video services
• backup for other types of links

This link for ISDN gives some additional background.

Frame Relay.  Frame relay is another approach that is often used to provide relatively cost effective, high speed connection between remote offices.  It is usually used in the following ways

• for high speed, low latency mesh or hub-and-spoke topologies between sites
• for both private and carrier provided networks

For additional information click on frame relay.

X.25. X.25 is often used in the following ways

• as a reliable WAN circuit or backbone
• as support for legacy applications

ATM.  ATM - Asynchronous Transfer Mode is typically used in the following applications

• as support for accelerating bandwidth requirements
• as support for multiple QoS applications in order to maintain particular standards for delays and data loss.

For additional information click on ATM.