Double-duty CSU/DSUs

Over the history of our writing these newsletters, one of the recurring themes has been that we highly recommend your upgrading your basic CSU/DSUs to newer, enhanced CSU/DSUs that have intelligent features for analyzing your network usage. The major reason we recommend this is so you can save money by " rightsizing " your permanent virtual circuits.

Now we have another reason for recommending these devices. It turns out that some of these CSU/DSUs - at least those made by Visual Networks - have a built-in protocol analyzer function. This means that in addition to watching your traffic at the frame relay level, you can actually set traps and analyze the data, locally or remotely, at the IP layer. If you're having a problem with a particular traffic type, you can simply set a trap for the data pattern in the CSU/DSU, rather than setting up a protocol analyzer and physically breaking into the circuit. This has a highly positive impact on WAN support costs, both in terms of the test gear spending that can be avoided and the need to dispatch technicians out to remote sites to find problems that would otherwise need an analyzer to resolve.

As with all innovations, there's a potential downside. Since a number of the installations of enhanced CSU/DSUs are as a part of a managed service, this means it's actually the service provider who is doing the analysis. And since the service provider is doing the analysis, it's at least theoretically possible that the service provider could trap and " see " your data. Visual Networks addresses this concern by only trapping a fairly small segment (a few hundred bytes) rather than whole packets and by enabling this feature to be turned off if necessary.

For those of us who spent years with an analyzer hunting a problem or wished we had an analyzer at every remote site, this is a really cool feature. But do the security risks outweigh the potential upside of having a protocol analyzer on every interface? We'll tackle that next time.

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@jwexler.com.

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