Natural MicroSystems Corporation

STRUCTURE AND EVOLUTION OF COMMUNICATIONS NETWORKS

Network components. There are three fundamental components of communications networks. The first component is the medium over which the communications signal is transmitted, such as conventional copper wires, fiber optic cable or radio waves. The second component is signaling, switching and other devices that create and manage the transmission of signals. The third component is standards or protocols that provide agreed languages that permit the various signaling, switching and other devices to communicate with one another. For example, the PSTN includes telephone lines, which transmit signals incorporating both the sound or data being communicated and the signals that route and manage the communication; telephones, switches, amplifiers and other devices that create, route, amplify and reproduce the signals; and numerous industry and country protocols governing the transmission and routing of the signals and the management of the network.

Principal public communications networks today include the PSTN and the Internet. Although each network is based on a distinct architecture, both the PSTN and the Internet require sophisticated equipment to transmit, route and manage communications and protocols that permit the equipment to communicate with other equipment between and within networks.

Convergence of voice and data. Historically, voice and data communications have been transmitted and managed on separate networks, each with distinct technologies, standards and protocols. Traditional telephone systems require that a dedicated connection, or circuit, be established and maintained for the duration of a call in order to transfer voice or data. Dedicated connections result in the poor use of bandwidth since no traffic travels through the circuit when users are silent, which can account for a significant amount of time during a transfer. IP networks differ fundamentally from circuit-switched networks in that the packet network’s resources and infrastructure can be shared simultaneously by several users and bandwidth can be flexibly allocated. Packet-based communications systems format the information to be transmitted, like e-mail, voice, fax and data, into a series of shorter digital packages of information called “packets.” Each of these packets is then transmitted over the network and is reassembled as a complete communication at the receiving end. IP networks offer a number of advantages over circuit-switched networks. Rather than requiring a dedicated circuit for each individual call, IP networks commingle packets of voice, fax and data from several communications sources on a single physical link, providing superior utilization of network resources. Additionally, this integration of voice and data communications makes possible an enrichment of services and an entire range of new, value-added applications.

Standards and protocols. IP and circuit-switched networks, deployed by service providers across multiple geographies, rely on an array of standards and protocols for communicating information among switches and other devices. The PSTN requires basic signaling software protocols such as

ISDN and SS7 in order to ensure that calls from one network to another are transmitted correctly. Similarly, the IP network requires a set of standards and protocols to route information correctly. For example, these standards include H.323 for the transmission of voice signals in an IP network. While these networks and protocols are distinct today, communications equipment vendors are striving to build equipment that enables the interconnection and interoperability of the different networks, protocols and standards.

Interoperability. The evolution of the packet-based network combined with the extensively deployed circuit-switched network creates the need for interoperability. Interoperable communications components can interconnect and work with both circuit and packet networks. Complete interoperability of these networks presents significant challenges. The PSTN, which consists of approximately 1.2 billion telephones worldwide, contains a large number of signaling protocol variants. The Internet utilizes a small number of open protocols. Many of these are still being defined and implemented by standards bodies and leading vendors. Interoperability requires the ability to execute all of the associated protocol variants, as well as the ability to process the data from its source to its destination format.

MARKET NEEDS

The explosive increase in data traffic, heightened competition, the need for network interoperability and the emergence of converged network infrastructures are causing service providers and enterprises to deploy new enhanced services and applications in order to compete more effectively. In addition, the increasing use of packet networks, which must interoperate with existing networks, requires network equipment and applications that can operate in both packet and circuit networks. Service providers require that their packet networks have the high levels of quality, availability, scalability and manageability traditionally associated with circuit networks. Finally, the emerging packet networks can support completely new enhanced services and applications, but only with new technologies such as traffic classification and bandwidth management.