Ever since Alexander Graham Bell invented the telephone in 1876, telephony systems have been a part of our life. More recently, with the advent of the Internet, much of our day-to-day communication (for example, e-mail) crosses an IP network (for example, the Internet). Today, these two worlds are merging, and companies can place phone calls over their existing data network infrastructures using a technology called Voice over IP (VoIP).

Just plug a microphone into your computer, start Internet Phone, and get in touch with other Internet Phone users. Internet Phone supports full-duplex conversations so you can speak and listen at the same time, just like with a real telephone. Graphic panels provide you with all the information you need, while an animated assistant lets you know exactly what's happening every step of the way. There's even a Quick-Dial menu for immediate access to the people you call the most. Whether you want to meet new friends, speak with your family, or make direct business contacts, Internet Phone is for you.

Call interception and eavesdropping are other major concerns on VoIP networks. The VOIPSA threat taxonomy efines eavesdropping as "a method by which an attacker is able to monitor the entire signaling and/or data stream between two or more VolP endpoints, but cannot or does not alter the data itself." Successful call interception is akin to wiretapping in that conversations of others can be stolen, recorded, and replayed without their knowledge. Obviously, an attacker who can intercept and store these data can make use of the data in other ways as well.

The advent of VoIP has led to revolutionary changes in the world of telecommunications. Information that was transported on traditional telephony infrastructures such as voice, video, and modulated data is transitioning to IP backbones. However, in this transition process, modulated data such as fax, modem, and text is often overlooked. Fax, modem, and text are treated like regular voice communications in many cases when in fact they have different transport requirements and usually need unique transport protocols for communication to be reliable.

However, there are two fundamental problems that currently pose a signifi cant risk to the scalability of VoIP to a large-population base along with guaranteed “industrial-grade” service levels. The fi rst problem is lack of de-facto intrinsic QoS in many of the IP networks deployed around the globe (both at the carrier level and at the enterprise level.) The second problem relates to end-to-end integrity of the signaling and bearer path for VoIP, specifi cally the fact that VoIP packets have a “diffi cult” time being carrier across fi rewalls, not only because of protocol considerations, but, at the practical level, because of the Network Address Translation (NAT) issues. Additionally, one can also cite overall security concerns as another potentially problematic issue.