Dial-up access
Encyclopedia
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 line
s. 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.
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. 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.
(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.
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.
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, 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.
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 coil
s, pair gain
, electric fence
s (usually in rural locations), and digital loop carrier
s 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.
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.
, 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".
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. Often there is no backchannel
capacity for the modem to communicate connection status to the end user or local computer. 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.
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.
Internet access
Many technologies and service plans for Internet access allow customers to connect to the Internet.Consumer use first became popular through dial-up connections in the 20th century....
that uses the facilities of the public switched telephone network
Public switched telephone network
The public switched telephone network is the network of the world's public circuit-switched telephone networks. It consists of telephone lines, fiber optic cables, microwave transmission links, cellular networks, communications satellites, and undersea telephone cables, all inter-connected by...
(PSTN) to establish a dialled connection to an Internet service provider
Internet service provider
An Internet service provider is a company that provides access to the Internet. Access ISPs directly connect customers to the Internet using copper wires, wireless or fiber-optic connections. Hosting ISPs lease server space for smaller businesses and host other people servers...
(ISP) via telephone line
Telephone line
A telephone line or telephone circuit is a single-user circuit on a telephone communication system...
s. The user's computer or router uses an attached modem
Modem
A modem is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data...
to encode and decode Internet Protocol
Internet Protocol
The Internet Protocol is the principal communications protocol used for relaying datagrams across an internetwork using the Internet Protocol Suite...
packets and control information into and from analogue audio frequency signals, respectively.
Availability
Dial-up connections to the Internet require no infrastructureInfrastructure
Infrastructure is basic physical and organizational structures needed for the operation of a society or enterprise, or the services and facilities necessary for an economy to function...
other than the telephone network
Telephone network
A telephone network is a telecommunications network used for telephone calls between two or more parties.There are a number of different types of 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
Rural Internet
Rural Internet is the access to the Internet from rural areas , which are settled places outside towns and cities. Inhabitants live in villages, hamlets, on farms and in other isolated houses...
areas, where broadband
Broadband
The term broadband refers to a telecommunications signal or device of greater bandwidth, in some sense, than another standard or usual signal or device . Different criteria for "broad" have been applied in different contexts and at different times...
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
Handshaking
In information technology, telecommunications, and related fields, handshaking is an automated process of negotiation that dynamically sets parameters of a communications channel established between two entities before normal communication over the channel begins...
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
Pew Research Center
The Pew Research Center is an American think tank organization based in Washington, D.C. that provides information on issues, attitudes and trends shaping the United States and the world. The Center and its projects receive funding from The Pew Charitable Trusts. In 1990, Donald S...
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. This has allowed Dial-up providers such as NetZero
NetZero
NetZero is an Internet service provider based in Woodland Hills, Los Angeles, California. It is a subsidiary of United Online, owner of Juno Online Services and BlueLight Internet Services. The current chairman, president, and CEO of United Online is Mark Goldston.- History :NetZero launched in...
to continue spending marketing dollars to obtain customers and commit to having U.S. based customer support.
Replacement by broadband
Broadband Internet accessBroadband Internet access
Broadband Internet access, often shortened to just "broadband", is a high data rate, low-latency connection to the Internet— typically contrasted with dial-up access using a 56 kbit/s modem or satellite Internet with inherently high latency....
(cable
Cable modem
A cable modem is a type of network bridge and modem that provides bi-directional data communication via radio frequency channels on a HFC and RFoG infrastructure. Cable modems are primarily used to deliver broadband Internet access in the form of cable Internet, taking advantage of the high...
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.
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.
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.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, 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.92V.92
V.92 is an ITU-T recommendation, titled Enhancements to Recommendation V.90, that establishes a modem standard allowing near 56 kb/s download and 48 kb/s upload rates. With V.92 PCM is used for both the upstream and downstream connections; previously 56K modems only used PCM for downstream...
protocol
Communications protocol
A communications protocol is a system of digital message formats and rules for exchanging those messages in or between computing systems and in telecommunications...
), 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 coil
Loading coil
In electronics, a loading coil or load coil is a coil that does not provide coupling to any other circuit, but is inserted in a circuit to increase its inductance. The need was discovered by Oliver Heaviside in studying the disappointing slow speed of the Transatlantic telegraph cable...
s, pair gain
Pair gain
In telephony, pair gain is a method of transmitting multiple POTS signals over the twisted pairs traditionally used for a single traditional subscriber line in telephone systems. Pair gain has the effect of creating additional subscriber lines...
, electric fence
Electric fence
An electric fence is a barrier that uses electric shocks to deter animals or people from crossing a boundary. The voltage of the shock may have effects ranging from uncomfortable, to painful or even lethal...
s (usually in rural locations), and digital loop carrier
Digital loop carrier
A digital loop carrier is a system which uses digital transmission to extend the range of the local loop farther than would be possible using only twisted pair copper wires...
s can also cripple connections to 20 kbit/s or lower.
Dial-up connections usually have latency
Latency (engineering)
Latency is a measure of time delay experienced in a system, the precise definition of which depends on the system and the time being measured. Latencies may have different meaning in different contexts.-Packet-switched networks:...
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
EverQuest
EverQuest, often shortened to EQ, is a 3D fantasy-themed massively multiplayer online role-playing game that was released on the 16th of March, 1999. The original design is credited to Brad McQuaid, Steve Clover, and Bill Trost...
, Red Faction
Red Faction
Red Faction is a first-person shooter video game developed by Volition, Inc. and published by THQ. It was released for the PlayStation 2, Microsoft Windows and Mac in 2001. A version for the Nokia N-Gage was developed by Monkeystone Games. The game was also re-developed as a top-down shooter for...
, Star Wars: Galaxies, Warcraft 3, Final Fantasy XI
Final Fantasy XI
, also known as Final Fantasy XI Online, is a MMORPG developed and published by Square as part of the Final Fantasy series. It was released in Japan on Sony's PlayStation 2 on May 16, 2002, and was released for Microsoft's Windows-based personal computers in November 2002...
, Phantasy Star Online
Phantasy Star Online
Phantasy Star Online is an online multiplayer action RPG title, originally released for the Dreamcast in 2000, bundled with a demo of Sonic Adventure 2. Another edition, entitled Phantasy Star Online ver.2, was released for Dreamcast the following year...
, Guild Wars
Guild Wars
Guild Wars is an episodic series of online 3D fantasy role-playing games developed by ArenaNet and published by NCsoft. Although often defined as an MMORPG the developers define it as a CORPG due to significant differences from the MMORPG genre. It provides two main modes of gameplay—a cooperative...
, Unreal Tournament
Unreal Tournament
Unreal Tournament is a futuristic first-person shooter video game co-developed by Epic Games and Digital Extremes. It was published in 1999 by GT Interactive. Retrospectively, the game has also been referred to as UT99 or UT Classic to differentiate it from its numbered sequels...
, Halo: Combat Evolved
Halo: Combat Evolved
Halo: Combat Evolved, frequently referred to as Halo: CE, or Halo 1, is a first-person shooter video game developed by Bungie and published by Microsoft Game Studios. The first game of the Halo franchise, it was released on November 15, 2001 as a launch title for the Xbox gaming system, and is...
, Audition, Quake 3: Arena, and Ragnarok Online
Ragnarok Online
Ragnarok Online , often referred to as RO, is a massively multiplayer online role-playing game or MMORPG created by GRAVITY Co., Ltd. based on the manhwa Ragnarok by Lee Myung-jin. It was first released in South Korea on 31 August 2002 for Microsoft Windows and has since been released in many other...
, are capable of running on 56k dial-up.
An increasing amount of Internet content such as streaming media
Streaming media
Streaming media is multimedia that is constantly received by and presented to an end-user while being delivered by a streaming provider.The term "presented" is used in this article in a general sense that includes audio or video playback. The name refers to the delivery method of the medium rather...
will not work at dial-up speeds.
Analog telephone lines are digitally switched and transported inside a Digital Signal 0
Digital Signal 0
Digital Signal 0 is a basic digital signaling rate of 64 kbit/s, corresponding to the capacity of one voice-frequency-equivalent channel...
once reaching the telephone company's equipment. Digital Signal 0
Digital Signal 0
Digital Signal 0 is a basic digital signaling rate of 64 kbit/s, corresponding to the capacity of one voice-frequency-equivalent channel...
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). 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.
Compression by the ISP
As telephone-based 56 kbit/s modems began losing popularity, some Internet Service Providers such as TurboUSA, NetzeroNetZero
NetZero is an Internet service provider based in Woodland Hills, Los Angeles, California. It is a subsidiary of United Online, owner of Juno Online Services and BlueLight Internet Services. The current chairman, president, and CEO of United Online is Mark Goldston.- History :NetZero launched in...
, CdotFree, TOAST.net, and Earthlink
EarthLink
EarthLink , is an Internet service provider headquartered in Atlanta, Georgia, USA. It claims 1.94 million subscribers.- Business :EarthLink provides a variety of Internet connection types, including dial-up, DSL, satellite, and cable. Both dial-up and high speed Internet access are available...
started using pre-compression to increase the throughput and maintain their customer base. As an example, Netscape
Netscape
Netscape Communications is a US computer services company, best known for Netscape Navigator, its web browser. When it was an independent company, its headquarters were in Mountain View, California...
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).| Connection | Bitrate Bitrate In telecommunications and computing, bit rate is the number of bits that are conveyed or processed per unit of time.... |
||||
|---|---|---|---|---|---|
| Modem 110 | 0.1 kbit/s | ||||
| Modem 300 (Bell 103 or V.21) | 0.3 kbit/s | ||||
| Modem 1200 (Bell 212A Bell 212A The Bell 212A modulation scheme defined a standard method of transmitting full-duplex asynchronous serial data at 1.2 kbit/s over analogue transmission lines. The equivalent, but incompatible ITU-T standard is V.22.... 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 V.92 V.92 is an ITU-T recommendation, titled Enhancements to Recommendation V.90, that establishes a modem standard allowing near 56 kb/s download and 48 kb/s upload rates. With V.92 PCM is used for both the upstream and downstream connections; previously 56K modems only used PCM for downstream... ) |
56.0/48.0 kbit/s | ||||
| Hardware compression (variable) (V.92 V.92 V.92 is an ITU-T recommendation, titled Enhancements to Recommendation V.90, that establishes a modem standard allowing near 56 kb/s download and 48 kb/s upload rates. With V.92 PCM is used for both the upstream and downstream connections; previously 56K modems only used PCM for downstream... /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-232RS-232
In telecommunications, RS-232 is the traditional name for a series of standards for serial binary single-ended data and control signals connecting between a DTE and a DCE . It is commonly used in computer serial ports...
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. Often there is no backchannel
Backchannel
Backchannel is the practice of using networked computers to maintain a real-time online conversation alongside live spoken remarks. The term was coined in the field of Linguistics to describe listeners' behaviours during verbal communication, Victor Yngve 1970.The term "backchannel" generally...
capacity for the modem to communicate connection status to the end user or local computer. 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.
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.