My Impressions of VoIP

We're using VoIP out here in Baghdad. I must say that it offers significant improvements in quality over what the military historically uses. The Cisco book "Voice Over IP Fundamentals" outlines a 150 ms ping time as a limit for reasonable call quality. But I have found respectable conversations can be had quite well even with ping times upwards of 1500 ms over satellite. There is minor lag between end stations, but the digital voice quality through the modern compression algorithms and modern real time delivery protocols are leaps and bounds above the beeping, static prone, hollow sound of traditional Army MSE voice.

I believe VoIP is a superior means to establish a local phone service than using a traditional PBX (private branch exchange). Rather than investing in the hardware and installation for separate phone lines, one single investment is made for a data network that happens to carry voice. QoS takes care of the prioritization to ensure voice quality does not diminish to heavy data traffic.

Now one major misconception is that VoIP means telephones on the Internet. VoIP is literally just Voice over IP. The voice chat in Apple's iChat, Yahoo Messenger or even TeamSpeak for video games are all implementations of VoIP. The compression algorithms and delivery mechanisms are nearly identical.

What many people don't realize is that most of their telephone calls are already 99% digital and traversing over data networks. IP and ATM have been relaying traffic over trunks for well over a decade. But since the '70s, SS7 (signaling system 7) being the venerable but still widely used hybrid of circuit switching and data packetization, has run the phone service. The only truly analog portion of a phone call in the past 30 years has been the local loop directly to the call office. What really drives the VoIP boat is the interface between a VoIP service provider and the existing PSTN system. The competition for telephone providers of yore was long distance rates. Today, with near ubiquitious access to the data network, the competition for voice providers is additional features for the same price.

Home users will see the least of these options - your standard PSTN features will remain with VoIP (caller ID, call waiting, *69, etc). The users that will push the envelope with be businesses. VoIP allows a virtual, contiguous addressing space for telephone number assignment. Corporations no longer have to lease dedicated circuits to link offices to maintain a linked call space. They can achieve this through a simple data VPN to and build voice on top of a corporate LAN. Corporations no longer have to lease dedicated circuits to maintain business links for priority calls. VoIP allows such an increase in data density on the common circuits that businesses get the same effect merely by using the Internet as a carrier. Corporations are also no longer locked into one telephone company for providing services and particular features. So long as they select a data carrier, an internal IT team can provide all the features they need from hardware managed internally - offering the exactly the features they need without haggling for it.

On a technical side, VoIP in it's current incarnation is not the miracle cure for communications. It has it's flaws and drawbacks.

Security Flaws:

- no encryption: I used a packet sniffer Ethereal just last week to watch the connectivity of the calls going through my network. A hacker could easily make several assumptions based on the data. One, it would be possible to find the call manager or voice gateway by analyzing which IP addresses are consistently accessed by known VoIP streams. This allows for targeting attacks directly on the service provider, spoofing the clients into being redirected from a man-in-the-middle, or faking service disruptions with seemingly legitimate source packets. By further analyzing source and destination IP's, it may become possible to target the call recipient as well (if they are VoIP). Furthermore, all of the data goes through the network via UDP using open protocols, so a sniffer could capture an entire session and recreate an entire conversation without either party ever being the wiser.

- remotely accessible hardware: Cisco ATA boxes (used by Vonage once, I'm not sure what they use now), call managers and VG248s are remotely configurable. For the devices that I have had my hands on in theater, none feature robust lockout schemes rendering each vulnerable to brute force attacks for access. I myself have remotely reprogrammed several "rogue" boxes on my network to lock them out of service.

Emergency Flaws:

- 911 access: This is often cited as the most dominant feature missing from VoIP. Regular PSTN phones receive their 48V operating power over the local loop directly from the call office. In the event of a power outage (local to a home per se), the phones continue to work off their analog line. VoIP requires the presence of power for the ATA and the broadband modem in order to maintain its connectivity to the service provider. Now, this is achievable through auxiliary power (generators, UPS, etc) but it is not as practical to end users as what they are accustomed to.

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