Hub vs. mesh PVC topologies

At a recent Network World Town Meeting, some attendees were curious about the pros and cons of designing their frame relay networks in a hub-and-spoke (or "star") topology compared to a fully meshed configuration. As a third option, of course, you could choose to implement a partially meshed network.

The topology that is right for you will depend on how often sites need to communicate with other sites, your performance requirements and your budget.

Hub-and-spoke topologies are generally the easiest to configure and the least expensive. In this topology, each site is linked to a central location by a permanent virtual circuit (PVC). Remote users can tap server resources at the central site and, when necessary, hop through to other remote sites. Since a monthly frame relay bill is the sum of the price of each port, each PVC and each access line, the fewer PVCs you run for a consistent level of traffic, the less expensive your bill will be.

For example, a six-site network in a hub-and-spoke configuration would require five PVCs (one from the hub site to each of the five other sites), while a fully meshed six-site network would require 15.

In addition, the hub-and-spoke network requires you to set up just five data link connection identifier pairs in your frame relay access equipment instead of 15, so configuration and management are simpler in this approach. If your remote sites tend to talk primarily to headquarters and rarely communicate directly with each other, there is not much justification to implement a fully meshed PVC network.

Later this week we'll fill you in about the options for building a more peer-oriented network.

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Steven Taylor, consultant and broadband packet evangelist, and Joanie Wexler, an independent networking technology editor and writer, team up to bring you this analysis and commentary. Taylor specializes in education and market analysis, and Wexler adds incisive reporting and research. For more detailed information on most of the topics discussed in this newsletter, connect to www.webtorials.com, the first Web site dedicated exclusively to market studies and technology tutorials in the Broadband Packet areas of Frame Relay, ATM, and IP. Feedback and additional topic ideas are welcome. Please contact taylor@webtorials.com or joanie_wexler@mindspring.com>

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