Internet Access-ADSL-ISDN – Information Technology Essay
Internet Access-ADSL-ISDN- Many people think that the Internet innovation, when in fact the essence of it has been around for over a quarter century. The Internet began as ARPAnet, a U.S. Department of Defense project to
create a nationwide computer network that would continue to function even if a large fraction of it were destroyed in a nuclear war or natural disaster. During the next two decades, the network that evolved was used primarily by academic institutions, scientists and government for research and communications. The appeal of the Internet to these bodies was obvious, as it allowed disparate institutions to connect to each others’ computing systems and databases, as well as share data via E-mail.
The nature of the Internet changed abruptly in 1992, when the U.S. government began pulling out of network management, and commercial entities offered Internet access to the general public for the first time. This change in focus marked the beginning of the Internet’s astonishing expansion.
According to a survey conducted by Commerce Net and Nielsen Media Research in early 1997, nearly one out of every four Americans over the age of 16 in an Internet user. And the number of users worldwide is believed to be well into the tens of millions. Other statistics are equally startling:
A CNN report stated that the Internet traffic in 1996 was 25 times what it was just two years earlier.
The market research group IntelliQuest pegged the number of Internet users in the U.S. in late 1996 at 47 million-a 34 percent increase over the first quarter of that year.
According to IBM, 146 countries currently have at least some level of Internet access.
The technology research firm IDG estimates that by century’s end, one billion people worldwide will have access to personal computers-more than doubling the computer-savvy population of 1996.
With this growing World Wide Web many businesses today need a faster Internet connection. Lawyers need to download and upload documents …
ISDN stands for Integrated Service Digital Network. It is a digital version of switched-circuit analogue telephone service. It was and developed to use the existing telephone wiring system is provided by local phone companies or PTTs ISDN was specifically designed to solve the low bandwith problems that small offices or dial-in users have with traditional telephone dial-in services. When data call is made using ISDN the WAN link is brought up for the duration of the call and is taken down when the call is connected from each site. Traffic engineering may require multiple BRI services or multiple PRIs at some sites. Once connected to the ISDN fabric by BRI or PRI interfaces, design of ISDN end-to-end services must be implemented. The BRI local loop is termintated at the customers premise at an NT1. The interface of the local loop at the NT1 is called the U refrence point. On the customer premise side of the NT1 is the S/T refrence point. ISDN cards and TA’s are like modems, but 5 times faster. They require special telephone lines, which cost a little (or a lot, depending on your phone company) more than normal phone lines.
ISDN calls are usually (in USA) charged by the minute, even for local calls, but this varies from state to state. If you’re quite nearby to someone you connect to constantly, you can sometimes order Centrex service, and get free calling always.
Businesses seeking fulltime connection are often better served by 56Kb/sec Frame Relay instead of ISDN, as it’s flat rate
Dan Keigel’s ISDN page. Website http://alumnus.caltech.edu/~dank/isdn/index.html
ADSL started out as the phone company’s way to compete with cable TV by delivering both TV and phone service on your plain old copper phone line. Now it’s also a good candidate for high speed Internet access.
The “A” stands for “Asymmetric”, meaning the phone company can send lots of data to you, but you can’t send much to them. Originally, only a tiny uplink of 16 or 64kbps was supported; recent flavors of ADSL support up to ten times that much.
Adsl stands for Asymmetrical Digital Subscriber line, a new technology that allows more data to be sent over an existing copper telephone lines (POTS). ADSL supports data rates of from 1.5 to 9Mbps when receiving data. We in the technical field would call this downloading. And from 16 to 640 Kbps when sending data. This is known as uploading. This will keep businesses on top and ahead of competition.
ADSL is one member of a continuum of last-mile transport systems called DSL, or Digital Subscriber Line, which can carry about 1 to 6 megabits/sec over copper lines. It does not include any way to make long distance data calls, or even local calls. That’s another matter entirely– one which is still up in the air. ADSL was originally designed so you still can use it as a regular phone line when the power goes out, which would be a big improvement over BRI ISDN.
For the moment, the only form of DSL really being deployed is HDSL, which is more or less a direct replacement for traditional T1 service. T1 lines have been around forever, but require technicians to tune the line to perfection; HDSL modems can handle dreadful lines cheerfully, so should be much cheaper to install and run.
Other kinds of DSL are coming soon. In general, the fastest DSL schemes only go a couple miles; the slowest can go farther. It’s a tradeoff.
Short for symmetric digital subscriber line, a technology that allows more data to be sent over existing copper telephone lines (POTS). SDSL supports data rates up to 3 Mbps.
SDSL works by sending digital pulses in the high-frequency area of telephone wires and can not operate simultaneously with voice connections over the same wires.
SDSL requires a special SDSL modem. SDSL is called symmetric because it supports the same data rates for upstream and downstream traffic. A similar technology that supports different data rates for upstream and downstream data is called asymmetric digital subscriber line (ADSL). ADSL is more popular in North America, whereas SDSL is being developed primarily in Europe. Refrence webopedia