Asymmetric PVCs can save big money

Customers who buy traditional data services, such as leased lines, are accustomed to their service price including two-way, or full-duplex, communications. In other words, one fee includes data flowing in both the "transmit" and "receive" directions.

Frame relay permanent virtual circuit (PVC) services, on the other hand, are often priced simplex, meaning that customers buy them separately in each direction. On the surface, this seems like a neat vendor scheme to make prices seem half as expensive. In actuality, though, it adds flexibility to the way users configure their links to better reflect traffic patterns and save them significant money.

Because of their familiarity with the leased-line model, most users tend to buy symmetrical frame relay services. If they are replacing a 56K bit/sec dedicated circuit with a frame relay PVC, they often buy a 56K bit/sec committed information rate (CIR) on that PVC in both directions. But most data flows, especially for client/server-type operations, are highly asymmetrical in nature: Users send a short query and receive a lot of information in return. When searching the Web, for example, a user connection to a site requires very little bandwidth, but downloading graphics and files in the other direction consumes much more.

Consider what asymmetrical links can save: Under AT&T's tariff, for example, a two-way 56K bit/sec PVC costs about $100 a month. If you specify a 16K bit/sec CIR on the transmit side to the server site and 56K bit/sec on the return path, though, your price drops to less than $70 per month - more than 30% less.

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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 http://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 @mindspring.com .

Finally: Frame relay SVCs - MCI this week due to become first major carrier to offer them. Network World, 6/9/98.

PSINet gets into frame relay game: Network World, 2/9/98.

Frame relay SVCs vs. Extranets: Network World, 11/3/97.

MCI rejiggers frame relay pricing: Network World, 5/5/97.

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