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Session Initiation Protocol (SIP): Controlling Convergent Networks (McGraw-Hill Communication Series)

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Telephone networks have come a long ways in the last 100 years. Or have they? If one looks at how a telephone network works, not much has changed. Connections are still made through “dedicated” circuits connected end to end for the duration of a call. While switchboard operators have been replaced by digital switching systems, the concept of connecting those circuits has not evolved much.

The telephone itself is still the same boring instrument, consisting of a speaker, a microphone, and a dial. About the most innovation we have seen there is the addition of a touch-tone dial and a display for caller names.

The networks themselves are still hierarchical switching networks, although some of the layers have been collapsed over the years. Calls are still routed through dedicated routes based on the digits dialed, and a tandem switch is still used to interconnect to other networks. This is a far cry from packet networks.

Packet networks have been around for many years, dedicated to transporting data from network to network. I can remember working on packet networks and building circuits during my tenure at the Bell System. I was fortunate that I was one of the few who worked on both voice and data networks because of my background in data and my expertise in data and voice networks.

Back then packet networks were used for dedicated computing purposes, providing the backbone for major computer networks. Public access was not provided, and the concept of connecting to the Internet did not yet exist (there was no public Internet at the time). In fact, there weren’t many personal computers then. Apple had emerged with the Apple II (I traded in my Apple I for the Apple II).

I remember when I first got a “portable” computer. It was one of the first “laptops,” if you will, although you would need a pretty big lap for this beast. It was an Osborne Computer, designed to be transportable (it had a really big handle) so that you could compute on the move. What that really meant was you could haul it from work to home and set it up on the kitchen table.

Of course, in those days there were no hot spots, Starbucks didn’t yet exist, and the only wireless telecommunications was radiotelephone. Yet even then, the concept of marrying the computer with the telephone was there. My Osborne had an RJ-11 jack on the back where you could plug in a telephone line for the modem that allowed you to connect the computer at a lightning-fast 300 baud.
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The Inside Text: Social, Cultural and Design Perspectives on SMS (The Computer Supported Cooperative Work Series)
The Inside Text: Social, Cultural and Design Perspectives on SMS (The Computer Supported Cooperative Work Series)
Mobile phones and the short-text messaging service (SMS or “text”) in particular
are new social phenomena, much marvelled at and much commented upon (See
Brown et al, 2002; Katz & Aakhus, 2002; Ling, 2004). This success is said to be
because mobiles allow new levels of micromanagement in an age of fraught and...
The Video Collection Revealed: Adobe Premiere Pro, After Effects, Soundbooth and Encore CS5
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Welcome to Th e Video Collection—Revealed. Th is book off ers creative projects, concise instructions, and complete coverage of basic to advanced video skills, helping you to create polished, professional-looking video. Use this book both in the classroom and as your own reference guide.

Th e text is
...
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Securing Windows Server 2003
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Windows Server 2003 has quite a number of uses. It can serve in a network support role, supplying services such as DHCP and DNS. It can...

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