Connection Selection Considerations

* Availability

* Bandwidth

* Ease of management

* Application traffic

* QoS and reliability

* Access control

When you design internetworks, you must make several key decisions concerning connectivity among different users or groups of users in your WAN environment.

When selecting a WAN connection, you should consider these factors:

■ Availability: Each method of connectivity has limits to its availability that is inherent in its design, usage, and implementation. For example, Frame Relay is not available in all geographic regions.

■ Bandwidth: WAN bandwidth is expensive, and organizations do not want to pay for more bandwidth than they need. Determining usage over the WAN is a necessary step in evaluating the most cost-effective WAN services for your needs.

■ Cost: WAN usage costs are typically 80 percent of the entire information services budget. Cost is a major consideration when different WAN services and different service providers are being evaluated. If, for example, you use the line for only 1 hour a day, you may want to select a DDR connection such as an asynchronous or ISDN connection.

Ease of management: Network designers are often concerned about the degree of difficulty associated with managing connections. Connection management refers to both the initial configuration at startup and the ongoing configuration tasks of normal operation. Traffic management is the ability of the connection to adjust to different rates of traffic, regardless of whether the traffic is steady or bursty in nature. Dedicated lines are often easier to manage than shared lines.

Application traffic: The application traffic may be many small packets, such as a terminal session, or very large packets, such as a file transfer.

Quality of service (QoS) and reliability: How critical is the traffic that is intended to travel over the link? A backup connection may be necessary.

Access control: A dedicated connection may help control access, but electronic commerce cannot occur on a wide scale unless consumers can access some portion of your network.

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