Following our recent newsletter on regulations requiring VoIP service providers to supply "lawful intercept" of voice traffic to authorities, we received some reader comments we'd like to share today.

David writes about one way for VoIP providers to track voice traffic. He notes that: "For traffic coming from people's homes, the service provider can look up the cable/DSL modem MAC address, the IP address assigned by their DHCP server, or the virtual circuit in use. Of course, with multiple users in the same home behind a firewall/NAT/router, more than the 'voice traffic of interest' would have to be captured, identified, and culled." He continues: "For enterprise users, the law enforcement authorities would have to work with the internal IT staff to identify the [traffic] ... using similar means."

David also raises some interesting constraints to this approach. For one, he points out that working with IT staff may result in the "person of interest" being tipped off. He also points out that many other persons' conversations would also be captured using this approach, raising certain privacy concerns for innocent users. He also observes that users who make a call over an 802.11 wireless network (like a Skype call from Starbucks) will make this approach all the more difficult to implement.

We would also like to point out that using a MAC or IP address is an approach used to help identify callers for E-911 services, allowing emergency responders to know the caller's location. However, unlike E-911 where users WANT to be found, we suppose most persons of interest to law enforcement will do their level best to beat any system to track their calls. And, while we can think of about a dozen ways to beat this address-based traffic identification, we'll leave it to the bad guys to figure that on their own.

Next time: Readers reply to our comments on the Universal Service Fund.

Steve Taylor is president of Distributed Networking Associates and publisher/editor-in-chief of Webtorials. Larry Hettick is a principal analyst at Current Analysis.