Dial-up Internet access


Dial-up 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 dialled 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.

Contents

Availability

Dial-up connections to the Internet require no infrastructure other than the telephone network. Where telephone access is widely available, dial-up remains useful. Broadband Dial-up 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 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, 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] This has allowed Dial-up providers such as NetZero to continue spending marketing dollars to obtain customers and commit to having U.S. based customer support.

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 dial-up.[citation needed]

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.[2][3]

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.[4][5][6]

Certainly high-speed DSL and Cable are 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 $19.95/month,[7] 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 a PC or netbook with a dial-up connection, making modern social networking possible through traditional dial-up Internet access. The affordability of dial-up Internet (and low-end PCs such as netbooks) makes this one viable option for social networking in a recessionary economy.

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, 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. First person shooter style games are the most sensitive to latency, making playing them impractical on dial-up. Many modern video games do not even include the option to use dial-up. However, some games such as Everquest, Red Faction, Star Wars: Galaxies, 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).[8] 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.[9]

Compression by the ISP

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 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 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 and the user can manually choose to view the uncompressed images at any time. 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).[10]

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

Performance assessment

Many modems were manufactured as independent communications devices connected to the computer via an RS-232 cable. Modems are capable of independently managing the connection and monitoring signal quality, and can adjust the data rate as line conditions change.

In analog serial communications modems, once the connection is established, the data communications session consumes all available bandwidth.[citation needed] Often there is no backchannel capacity for the modem to communicate connection status to the end user or local computer.[citation needed] During the connection negotiation phase, modems transmit the connection speed to the attached computer in status reports. If the base data rate changes at a later time, there is no way to indicate this change to the local computer during the data communications session.[citation needed]

Although much more capable serial communications such as USB are now used, and in approximately 1992 the soft modem was developed that uses the internal computer CPU to handle modem communications, there is still no defined industry standard backchannel method available to indicate status information such as the current base rate and actual compression ratio, to the user of the local computer.

References

  1. ^ "Many Dial-Up Users Don't Want Broadband". Associated Press (Fox News Channel). 2008-07-07. http://www.foxnews.com/story/0,2933,375624,00.html. Retrieved 2009-11-03. 
  2. ^ LaVallee, Andrew (2009-02-27). "Could You Go Back to Dial-Up? - Digits - WSJ.com". Wall Street Journal (Dow Jones). http://blogs.wsj.com/digits/2009/02/27/could-you-go-back-to-dial-up/. Retrieved 2009-02-27. 
  3. ^ "Recession Has Many Holding on to Dirt-Cheap Dial-Up". Fox News. 2009-02-26. http://www.foxnews.com/story/0,2933,500686,00.html. Retrieved 2009-02-27. 
  4. ^ "Recession Has Many Holding on to Dirt-Cheap Dial-Up". Fox News. 2009-02-26. http://www.foxnews.com/story/0,2933,500686,00.html. Retrieved 2009-02-27. 
  5. ^ "The Digital Divide - washingtonpost.com". The Washington Post. 2009-02-28. http://www.washingtonpost.com/wp-dyn/content/article/2009/02/27/AR2009022702749.html?hpid=topnews. Retrieved 2009-02-28. 
  6. ^ LaVallee, Andrew (2009-02-27). "Could You Go Back to Dial-Up? - Digits - WSJ.com". Wall Street Journal (Dow Jones). http://blogs.wsj.com/digits/2009/02/27/could-you-go-back-to-dial-up/. Retrieved 2009-02-27. 
  7. ^ "AT&T Residential Home Phone Service - CT". AT&T Intellectual Property. AT&T Intellectual Property. http://www.att.com/gen/general?pid=11523. Retrieved 2009-03-01. 
  8. ^ Pavel Mitronov. "Modem compression: V.44 against V.42bis". Digit-Life.com. http://www.digit-life.com/articles/compressv44vsv42bis. Retrieved 2008-02-18. 
  9. ^ Karl Willdig. "What You Need to Know about Modems". Fermilab Data Communications and Networking Group. Fermi National Accelerator Laboratory. http://fndcg0.fnal.gov/Net/modm8-94.txt. Retrieved 2008-02-18. 
  10. ^ "Data communication over the telephone network". International Telecommunication Union. http://www.itu.int/rec/T-REC-V/en. Retrieved 2008-02-18. 

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