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Dial-Up

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Dial-Up

Main article: Internet access


Dial-up Internet access is a form of Internet access that uses the facilities of the public switched telephone network (PSTN) to establish a dialed connection to an Internet service provider (ISP) via telephone lines. The user's computer or router uses an attached modem to encode and decode Internet Protocol packets and control information into and from analogue audio frequency signals, respectively.

Availability

Dial-up connections to the Internet require no infrastructure other than the telephone network and the modems and servers needed to make and answer the calls. Where telephone access is widely available, dial-up remains useful and it is often the only choice available for rural or remote areas, where broadband installations are not prevalent due to low population density, and high infrastructure cost. Dial-up access may also be an alternative for users on limited budgets, as it is offered 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 telephone connection (up to several seconds, depending on the location) and perform configuration 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, ISP or phone company terminates the connection. Internet service providers will often set a limit on connection durations to allow sharing of resources, and will disconnect the user—requiring reconnection and the costs and delays associated with it. Technically inclined users often find a way to disable the auto-disconnect program such that they can remain connected for days.

A 2008 Pew Internet and American Life Project study states that only 10 percent of US adults still used dial-up Internet access. Reasons for retaining dial-up access include lack of infrastructure and high broadband prices.[1] According to the United States Federal Communications Commission (FCC), 6% used dial-up in 2010.[2]

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 of 700 kbit/s or higher for two-thirds more than the price of dial-up on average.[2] In addition broadband connections are "always on", thus avoiding the need to connect and disconnect at the start and end of each session. Finally, unlike dial-up, broadband does not require exclusive use of a phone line and so one can access the Internet and at the same time make and receive voice phone calls without having a second phone line.

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 dial-up ISPs have responded to the increased competition by lowering their rates and making dial-up an attractive option for those who merely want email access or basic web browsing.[3][4]

Recession and its effect on service

News reports in 2009 noted a resurgence of dial-up access in the U.S. resulting from a recessionary economy, as a more affordable way of accessing the Internet.[5][6][7] AOL added 200,000 dial-up customers in 2011. The average monthly price of dial-up Internet is $22, compared to $37 for broadband, according to the FCC.[2]

High-speed DSL and cable are often available without local phone service, but the cost of this "naked" service is noticeably higher. AT&T offers basic DSL ("Direct Express") without a phone line for $24.95/month,[8] potentially negating any savings from canceling the phone service. Cable companies do not financially penalize a subscriber for not having a local phone; however cable Internet services are usually more expensive if the customer does not subscribe to their television services.

Social networking sites such as Facebook and Twitter feature mobile editions with limited graphics and reduced functionality, designed for slow Internet connections on mobile devices. These cut-down websites will also perform well on dial-up connections, making modern social networking possible through traditional dial-up Internet access. The affordability of dial-up Internet (and low-end computers such as netbooks) makes this one viable option for social networking in a recessionary economy.

Performance

"Dial up modem noises"
File:Dial up modem noises.ogg
Typical noises of dial-up modem while a modem is establishing connection with a local ISP-server in order to get access to the public Internet.

Problems playing this file? See media help.

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, or in a rural area, many miles from the phone exchange. Other things such as long loops, loading coils, pair gain, electric fences (usually in rural locations), and digital loop carriers can also cripple connections to 20 kbit/s or lower.

Dial-up connections usually have latency as high as 300 ms or even more; this is longer than for many forms of broadband, such as cable or DSL, but typically less than satellite connections. Longer latency can make online gaming or video conferencing difficult, if not impossible.

Many modern video games do not even include the option to use dial-up. However, some games such as Everquest, Red Faction, Warcraft 3, Final Fantasy XI, Phantasy Star Online, Guild Wars, Unreal Tournament, Halo: Combat Evolved, Audition, Quake 3: Arena, and Ragnarok Online, are capable of running on 56k dial-up.

An increasing amount of Internet content such as streaming media will not work at dial-up speeds.

Analog telephone lines are digitally switched and transported inside a Digital Signal 0 once reaching the telephone company's equipment. Digital Signal 0 is 64 kbit/s; therefore a 56 kbit/s connection is the highest that will ever be possible with analog phone lines.

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).[9] 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.[10]

Compression by the ISP

Main article: Web accelerator

As telephone-based 56 kbit/s modems began losing popularity, some Internet service providers such as TurboUSA, Netzero, CdotFree, TOAST.net, and Earthlink started using compressing proxy servers 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 a proxy 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 perceived speed is dramatically improved. The user may be able to choose to view the uncompressed images instead, if desired. ISPs employing this approach may advertise it as "DSL speeds over regular phone lines" or simply "high speed dial-up".

List of dial-up speeds

Note that the values given are maximum values, and actual values may be slower under certain conditions (for example, noisy phone lines).[11]

Connection Bitrate
Modem 110 0.1 kbit/s
Modem 300 (Bell 103 or V.21) 0.3 kbit/s
Modem 1200 (Bell 212A or V.22) 1.2 kbit/s
Modem 2400 (V.22bis) 2.4 kbit/s
Modem 2400 (V.26bis) 2.4 kbit/s
Modem 4800 (V.27ter) 4.8 kbit/s
Modem 9600 (V.32) 9.6 kbit/s
Modem 14.4 (V.32bis) 14.4 kbit/s
Modem 28.8 (V.34) 28.8 kbit/s
Modem 33.6 (V.34) 33.6 kbit/s
Modem 56k (V.90) 56.0/33.6 kbit/s
Modem 56k (V.92) 56.0/48.0 kbit/s
Hardware compression (variable) (V.92/V.44) 56.0 - 320.0 kbit/s
Server-side web compression (variable) 200.0 - 1000.0 kbit/s

References

Internet portal
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