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SSP Project Summary: |
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This growth, and change in the nature of traffic represents a huge opportunity and headache for telecoms operators because although the volumes may be growing at 1000% p.a. revenues are not. The only way to remain competitive in this rapidly changing market place will be to most effectively harness the power of emerging network technologies.
Every ten years or so, the most basic of telecommunications services, the telephone, undergoes a dramatic change. In the 1950s, the introduction of transatlantic coax cables allowed direct-dial international calls; in the 1960s, digital transmission and switching drastically improved the audio quality; in the 1970s, programmable switches enabled touch-tone dialing and local services such as call waiting; and in the 1980s, the widespread implementation of out-of-band common-channel signaling systems like Signaling System 7 (SS7) made services such as 800- numbers possible. These changes define a trajectory from analog transmission and signaling to digital, circuit-switched transmission and packet-based signaling. In the 1990s, Internet telephony marks the latest step along this slow path to an all-packet infrastructure.
Its history actually began 20 years earlier. The first papers on how to transmit voice were published in the early 1970s, and the first Internet packet audio experiments took place in August 1974, when real-time packet voice was demonstrated between the University of Southern California's Information Sciences Institute and the Massachusetts Institute of Technology's Lincoln Laboratory. The first Request for Comments for packet voice, RFC 741, was published in 1977. Internet telephony developed relatively slowly until 1991 and 1992, when packet-audio experiments were performed on DARTnet and the first IETF meetings were multicast across the Mbone. I made my first Internet phone call to Switzerland around 1992, but such communications were limited to research labs and targeted primarily at multiparty teleconferences, rather than person-to-person phone calls. Even if you had Internet connectivity of sufficient bandwidth, there was no way to reach a particular person short of exchanging each other's email addresses by email or regular telephone.
In 1995, Vocaltec introduced one of the first PC-based Internet telephony applications. Gateways to the public switched telephone system (PSTN) followed shortly thereafter, although most were initially limited to a few analog ports. There was also a shift away from using end systems like PCs, which connect directly to the Internet, and toward using regular telephones on both ends instead.
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mario@epcc.ed.ac.uk
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