IP Telephony Overview

Internet Protocol (IP) telephony is the emerging communications technology arising from the convergence of the worldwide data infrastructure and the telecommunications network.

Until now, the voice world and the data world have been largely separate. Voice traffic moves on circuit-switched networks where a fixed path is established at call set-up and maintained for the duration of the call. Network resources are allocated to the call, leading to a logical model of time-based pricing. Over the years, millions of millions of dollars have been invested in circuit-switched technology and these networks are considered extremely reliable pretty much worldwide. Voice traffic growth is pretty much in the single digit category.

Data traffic has moved on packet-switched networks. Messages or files are broken up into small packets and each packet is sent out onto the network on its own, typically with header information containing the needed destination address and other descriptors. The series of packets moves through the network individually and different packets may take different paths through the mesh of routers and switches. Packets do not necessarily arrive at the destination in the same order they left the sender, and some packets may be lost along the way. Network resources are shared, however, leading to a very efficient architecture. Often, packet-switched network access is priced at a fixed rate, depending on guaranteed bandwidth, but sometimes the network is priced on a usage basis, with users charged for the number of bytes they transmit.

The future is heading towards converged networks. Converged networks serve to lower the costs and maintain the reliability associated with the telecommunications network, while combining more efficient use of bandwidth and the new value-added services being made available over the data networks. The ultimate goal of course is to have an efficient, all-inclusive, highly reliable, and always available transport for multimedia communications, collaborative computing, and e-commerce. In this way, IP telephony represents a new paradigm for worldwide communications.

IP telephony really got started as Internet telephony. The concept was to use the Internet for voice communications in a PC-to-PC dialogue. If packets are packets, then voice should be as easy to digitize and send via the Internet as any text message. Almost. The motive of course was toll avoidance. Since most people can access the Internet via a local phone call, which is typically free in many North American locals, and since many people pay a fixed monthly ISP fee for nearly unlimited usage, the view is that long distance calls would be free. But this was only the beginning. Today, the drivers for IP telephony include:

• Toll avoidance by the end user.
• Access charge avoidance by competitive exchange carriers and long distance carriers.
• New services, such as the integration of customer records with voice communications.
• Preference for and experience with the Internet by youth population.
• Streamlined networks (one network to manage).
• Declining PC prices, which makes Internet access more affordable.
• Portability of Internet access.
• Growing role of electronic-commerce.

Against this list of motivators we should also consider a list of restraints, items which are preventing IP telephony from happening, or from taking off in the near future. These include:

• A general lack of technical expertise, certainly compared to circuit switched technology in the wide area network homes of the carriers.
• Uncertain regulatory environment.
• Ability of the current incumbents to lower their prices for circuit switched calls, thereby reducing the motivation for many to move to packet voice.
• A lack of knowledge in the user community.
• Lower quality of voice signals when carried over packet networks.
• Lack of unified standards, leading to non-interoperability between hardware vendors and networks.
• Unproven reliability.

While the list of negative is impressive, the fact is that there are too many large companies pouring too much money into voice-over-IP technology for these technical issues to remain unsolved. The regulatory environment is something else however.

The generally accepted notion today is this: Voice over IP is really not a question of IF it will happen and IF it will become mainstream, because the long term benefits and economics are too compelling; the question is only WHEN.