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Dial-up access
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Dial-up Internet Access is a form of Internet access via telephone lines. The user's computer or router uses an attached modem connected to a telephone line to dial into an Internet service provider's (ISP) node to establish a modem-to-modem link, which is then used to route Internet Protocol packets between the user's equipment and hosts on the Internet.
The term was coined during the early days of computer telecommunications when modems were needed to connect dumb terminals or computers running terminal emulator software to mainframes, minicomputers, online services and bulletin board systems via a telephone line.
-up connections to the Internet require no infrastructure other than the telephone network.
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Encyclopedia
Dial-up Internet Access is a form of Internet access via telephone lines. The user's computer or router uses an attached modem connected to a telephone line to dial into an Internet service provider's (ISP) node to establish a modem-to-modem link, which is then used to route Internet Protocol packets between the user's equipment and hosts on the Internet.
The term was coined during the early days of computer telecommunications when modems were needed to connect dumb terminals or computers running terminal emulator software to mainframes, minicomputers, online services and bulletin board systems via a telephone line.
Availability
Dial-up connections to the Internet require no infrastructure other than the telephone network. As telephone access is widely available, dial-up remains useful to travelers. Dial-up is usually the only choice available for rural or remote areas where broadband installations are not prevalent due to low population and demand. Dial-up access may also be an alternative for users on limited budgets as it is offered for free by some ISPs, though broadband is increasingly available at lower prices in many countries due to market competition.
Dial-up requires time to establish a usable telephone connection (several seconds, depending on the location) and perform handshaking for protocol synchronization before data transfers can take place. In locales with telephone connection charges, each connection incurs an incremental cost. If calls are time-metered, the duration of the connection incurs costs.
Dial-up access is a transient connection, because either the user or the ISP terminates the connection. Internet service providers will often set a limit on connection durations to prevent hogging of access, and will disconnect the user — requiring reconnection and the costs and delays associated with it.
A 2008 Pew Internet and American Life Project study states that only 10 percent of American adults still use dial-up Internet access. Reasons for retaining dial-up access span from lack of infrastructure to high broadband prices.
Performance
Modern dial-up modems typically have a maximum theoretical transfer speed of 56 kbit/s (using the V.90 or V.92 protocol), although in most cases 40-50 kbit/s is the norm. Factors such as phone line noise as well as the quality of the modem itself play a large part in determining connection speeds. Some connections may be as low as 20 kbit/s in extremely "noisy" environments, such as in a hotel room where the phone line is shared with many extensions.
Dial-up connections usually have latency as high as 400 ms or even more, which can make online gaming or video conferencing difficult, if not impossible. First person shooter style games are the most sensitive to latency, making playing them impractical on dial-up. However, some games such as Star Wars: Galaxies, The Sims Online, Warcraft 3, Guild Wars, Unreal Tournament, and Audition are capable of running on 56k dial-up.
An increasing amount of Internet content such as streaming media will not work at dialup speeds.
Using compression to exceed 56k
The V.42, V.42bis and V.44 standards allow modems to accept uncompressed data at a rate faster than the line rate. These algorithms use data compression to achieve higher throughput.
For instance, a 53.3 kbit/s connection with V.44 can transmit up to 53.3 * 6
320 kbit/s if the offered data stream can be compressed that much. However, the compressibility of data tends to vary continuously, for example, due to the transfer of already-compressed files (ZIP files, JPEG images, MP3 audio, MPEG video). A modem might be sending compressed files at approximately 50 kbit/s, uncompressed files at 160 kbit/s, and pure text at 320 kbit/s, or any rate in this range. In such situations a small amount of memory in the modem, a buffer, is used to hold the data while it is being compressed and sent across the phone line, but in order to prevent buffer overflow, it sometimes becomes necessary to tell the computer to pause the datastream. This is accomplished through hardware flow control using extra pins on the modem–computer connection. The computer is then set to supply the modem at some higher rate, and the modem will signal the computer when to start or stop sending data.
Compression by the ISP
As telephone-based 56 kbit/s modems began losing popularity, some Internet Service Providers such as Netzero, Juno, and Earthlink started using pre-compression to increase the throughput and maintain their customer base. As an example, Netscape ISP uses a compression program that squeezes images, text, and other objects at the server, just prior to sending them across the phone line. The server-side compression operates much more efficiently than the "on-the-fly" compression of V.44-enabled modems. Typically website text is compacted to 5% thus increasing effective throughput to approximately 1000 kbit/s, and images are lossy-compressed to 15-20% increasing throughput to about 350 kbit/s.
The drawback of this approach is a loss in quality, where the graphics acquire more compression artifacts taking-on a blurry appearance, however the speed is dramatically improved and the user can manually choose to view the uncompressed images at any time. The ISPs employing this approach advertise it as "DSL speeds over regular phone lines" or simply "high speed dialup".
Replacement by broadband
Broadband Internet access (cable and DSL) has been replacing dial-up access in many parts of the world. Broadband connections typically offer speeds 700 kbit/s or higher for approximately the same price as dialup.
However, many areas still remain without high speed Internet despite the eagerness of potential customers. This can be attributed to population, location, or sometimes ISPs' lack of interest due to little chance of profitability and high costs to build the required infrastructure. Some Dialup ISPs have responded to the increased competition by lowering their rates to as low as $5 a month making dialup an attractive option for those who merely want email access or basic web browsing.
Recession and its effect on service
Many recent articlesnote the resurgence of dial-up access in the face of an increasingly difficult global economy. Dial-up is a more affordable way of accessing the internet than high-speed services. For example, DSL and dial-up both require a phone line. The average cost for a phone line in the United States is $17 per month ([AT&T]). This in addition to America Online's basic plan at $9.95 per month would equal a total of $26.95 per month. A phone line for $17 per month plus an additional $30 per month for DSL ($30 per month is the average cost for DSL ([ATT]) in the United States (excluding introductory or "$xx for 3 months" offers) equals $47 per month. Thus the savings of dial-up over DSL would be 42% per month, or $240.60 per year. With NetZero internet at $4.97 per month the savings would be an even greater 53% or $300.36.
Certainly high-speed DSL is available without local phone service, but the cost of this "naked" service is noticeably higher; this is likely to offset the cost of the provider losing the profit of the phone line service. The choice from AT&T would be basic phone and DSL ($17/month for phone and $19/month for DSL equals $36/month) or basic DSL ("Direct Express") without a phone line for $35/month) Thus, one can conclude that there really is no savings at all.
List of dialup speeds
Note that the values given are maximum values, and actual values may be slower under certain conditions (for example, noisy phone lines).
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