One of the hottest technologies these days is voice communication over packet-switched data networks. This is known as voice over Internet protocol (VoIP). Hardy (2003) defines VoIP as “the interactive voice exchange capability carried over packet switched transport employing the Internet protocol.” With VoIP, voice signal from the sender is digitized into packets that are transmitted to the receiver through a network,which often includes the Internet. As the Internet is a free resource, the communication cost of VoIP is much lower than that of traditional telephone systems. This is a major advantage of VoIP. VoIP system also increases the efficiency and service quality of businesses. As a result of VoIP, many advanced applications can be built and these include unified messaging, video conferencing, and ring list. But VoIP is not without its limitations. Its main drawback is low reliability. It also suffers from uncertain quality of voice transmission. In addition, it cannot guarantee security because it uses public networks. Although the idea of VoIP was known from the 1970s, it did not become commercially viable until 1995, when Vocaltec became the first company to produce the first commercially available VoIP product (Varshney et al., 2002).
Key Terms in this Chapter
Internet Session: Internet session is a connection between a client and a server computer. It is essential for exchange of information between two computers.
Circuit Switched Network: Circuit switched network is a network in which a dedicated connection exists between two end-users. It is typically used for voice communication.
Packet-Switched Network: Packet-switched network is a network which allows data packets to flow through it using the store and forward method.
QoS (quality of service): It refers to the capability to provide resource guarantee and service differentiation to applications. Resource guarantee implies that an application can get the amount of network resource it requests. Service differentiation provides higher priority to those applications with stringent time constraints. For example, when using QoS, video conferencing can be given higher priority than activities like file sharing.
Best-Effort Model: Best-effort model is a network model in which the network does not provide any resource guarantee to the data delivery. It only provides the “best effort” which means “try its best to serve the user.”
PSTN (Public Switched Telephone Network): It provides traditional telephone service to residential customers.
Round-Trip Delay: Round-trip delay is the total time taken for a packet to go from a client to the server and then return from the server to the client.
LAN (Local Area Network): It is a computer network connecting computers in a small local area, such as home, office, campus, or building.
WAN (Wide Area Network): It is a computer network connecting computers in a large geographical area that may be a country or region. One example of WAN is the Internet.