Wi-Fi Exposure

Dave Molta replies: Almost all WLAN radios are low-power devices, with output of less than 100 milliwatts. By way of comparison, most walkie-talkies sold to kids have an output power of 100 milliwatts--and unlike WLAN radios, those devices are held to the head, increasing the radiation exposure.

Upgrading from a 2-dBi to a 6-dBi WLAN radio antenna would result in an EIRP (effective isotropic radiated power) of 230 milliwatts in immediate proximity to the antenna. This output is still a lot less than the 1,000 milliwatts or more generated by cell phones.

Most of the studies I've read about the potential health effects of cell-phone radiation conclude that the risks are negligible. It seems clear that for WLAN devices, the risks would be even lower. But if you want to be extra cautious, consider some of the new MIMO (multiple input/ multiple output) systems that extend range without increasing radio output power.

RANCID Perils

In "RANCID Tool Keeps Config Files Clean" (July 21), Bruce Boardman suggests keeping "./" in the user's path variable to provide ease of use for running commands in the current working directory. However, it's worth mentioning that this practice is not advisable for root users, given the chance of unknowingly running a Trojaned command. For that matter, sysadmins in general probably shouldn't use this, as an attacker could leverage it to get escalated access to a system.John Kinsella
Director of Security Services
KlioSystems Consulting

[email protected]

MPLS Facts

I applaud Bruce Boardman's "just the facts" approach to Multiprotocol Label Switching ("New WAN Order" Aug. 4). But though Boardman deserves praise for boiling down this complex topic, I wish he had devoted a few more words to discussing how MPLS differs from static frame and why customers are adopting the technology.

As for AT&T [winner of Network Computing's Editor's Choice award for WAN services], I doubt it can meet its stated average round-trip delay in the United States of 39 ms, or the 1-ms jitter it also claims. I wonder how AT&T plans to report the actual performance data to the customer, and what credits or payments it will provide if the data falls short of the service level agreement. Apparently, the vendor's BusinessDirect portal doesn't furnish such data.

Technology problems like BGP flapping continue to plague the MPLS offering. So does difficulty in reporting on network-utilization metrics such as traffic types, top talkers and real-time stats.

Bandwidth comes in two flavors if the customer wants multicast: T1 and T3. But if you multiplex T1s with the "IMA" deployment leveraging ATM, you might as well forget multicasting.William R. Wright
Program Manager
Employer and e-mail address withheld by request

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Tell Us How You Really FeelSend e-mail to [email protected], fax to (516) 562-7293 or mail letters to Network Computing, 600 Community Drive, Manhasset, NY 11030. Include your name, title, company name, e-mail address and phone number. All correspondence becomes the property of Network Computing.