Content Overview Government and commercial organizations have used telephone services for over 100 years. During that time, technologies have advanced to provide more services, more reliability, and lower cost to the public and clients. In the past decade, with huge advances in computing power and networking technology, the capability for enterprises to leverage new opportunities demands that voice, video, and data services be converged over a single network. This module describes the concept of converged networks that carry voice, video, and data. The module begins with a brief description of telephone services that companies have come to rely on prior to the movement toward converged networks. The first lesson describes traditional telephone company services and defines many of the legacy terms and concepts that affect the network convergence technologies presented in this course. The second lesson illustrates the concept of converged networks through examples of architectures and network models that accommodate the integrated services within converged networks. The lesson explains the vision Cisco has of the Intelligent Information Network (IIN), Cisco Service-Oriented Network Architecture (SONA), and Cisco Enterprise Architectures, with a focus on the traffic conditions and requirements imposed by converged applications. Web Links At-a-Glance: What is Cisco SONA?
 http://www.cisco.com/application/pdf/en/us/guest /
netsol/ns477/c643/cdccont_0900aecd8039b324.pdf INTELLIGENT INFORMATION NETWORK; BUILDING BUSINESS TRANSPARENCY AND AGILITY
 http://www.cisco.com/warp/public/779/largeent/
landingPage/iin/pdf/cisco_refreshbrochure_05132_r2.pdf
Content 1.1 The Evolution of Telephony in the Enterprise 1.1.1 A Basic Telephone System Businesses have used the telephone for over 100 years. Over this period, there have been many significant changes to the equipment that is used and the companies who provide the services. Today VoIP is rapidly becoming the dominant technology. However, it is important to review past technologies since they may have significant impact on network deployment within the enterprise. A telephone system consists of four elements as shown in Figure : Figures and show examples of telephones over the years. There are three ways for a subscriber to connect to the telephone exchange: Figure shows the components of a modern telephone system that connects across the world through a variety of media.
Content 1.1 The Evolution of Telephony in the Enterprise 1.1.2 Traditional Telephone Company Services The Public Switched Telephone Network (PSTN) in North America and the Postal, Telephone and Telegraph (PTT) services, in much of the rest of the world, carry analog voice over copper wires. This basic telephone service is often called POTS. In some places, POTS means the Post Office Telephone Service or Post Office Telephone System. However, as legislation removed telephone services from the control of national post offices, the term became more widely known as meaning “plain old telephone service.” POTS remains the basic form of residential and small business telephone service nearly everywhere in the world. Until the introduction of mobile telephones, POTS was the only telephone service that most people knew. POTS has been available almost since the introduction of the telephone system in the late 19th century. Telephone service remained mostly unchanged to the average user since the middle of the 20th century, despite the introduction of electronic telephone exchanges into the PSTN and PTT. Here are some of the POTS services that are available:
Content 1.1 The Evolution of Telephony in the Enterprise 1.1.3 Digital Telephone Technologies The Public Switched Telephone Network (PSTN) has evolved towards digital telephony and the capacity and quality of the network has improved. In the 1970s, telephone companies (telcos) began modifying their analog telephone networks by upgrading the long-haul transmission sections of their networks with fiber optic technology. Digital transmission made it possible to carry multiple digitized switched circuits on a single transmission medium (known as multiplexing). Although the user equipment remains largely analog-based, the switches at the telephone exchange (called the analog voice signal switches) convert the analog signals to digital signals. Recently, telcos began moving their digital networks closer to the customer premises. This change has all but relegated the analog local loop to legacy status. Generally, telcos offer digital transport services in one of two forms. Integrated Services Digital Network (ISDN) provides a digital loop from the exchange (or central office) to the customer premises. In North America and Japan, transmission 1 (T1) carrier technology provides trunk lines between exchanges. Europe 1 (E1), used in Europe, is a similar carrier, though the two services differ in these ways: