Compare and Contrast

Dial-up and DSL

            A dial-up line is a temporary connection that uses one or more analog telephon lines for communications, and a digital subscriber line or DSL uses broadband to transmit a greater number of bytes on a standard twisted-pair cable.

Dial-up and DSL uses telephone line to connect to the internet. Until now dial-up and DSL are using by home user people for their internet connection.

Although they both using telephone line, it is more preferable to  use DSL than dial-up, because dial-up connection is not permanent, each time a call is placed, the telephone company switching offices select the line to use to establish connection. Even though dial-up is not permanent its one advantage is that it cost no more than making a regular telephone call.

DSL has higher quality than dial-up, because dial-up is not permanent and DSL faster than dial-up in terms of internet connection. DSL’s speed is 1.54 Mbps up to 8.45 Mbps, downstream and 128 Kbps up to 640 Kbps, upstream while Modern dial-up modems typically have a maximum theoretical transfer speed of 56 kbit/s, 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 kilometres from the exchange. Other things such as long loops, loading coils, pair gain, electric fences, and digital loop carriers can also cripple connections to 20 kbit/s or lower. Because DSL is faster than dial-up, you can save time in using DSL than a dial-up connection.

Dial-up line needs load to connect with internet while DSL payment is depend upon the telephone line company for example in PLDT, the payment is 999 per month not included the telephone bill. Even though DSL is expensive it is popular because of its conveniency.

According to wikipedia, the implementation of Digital Subscriber Line technology originally was part of the Integrated Services Digital Network or ISDN specification published in 1984 by the CCITT and ITU as part of Recommendation I.120, later reused as ISDN Digital Subscriber Line or IDSL. Engineers have developed higher-speed DSL facilities such as High bit rate Digital Subscriber Line or HDSL and Symmetric Digital Subscriber Line or SDSL to provision traditional Digital Signal 1 or DS1 services over standard copper pair facilities. Consumer-oriented Asymmetric Digital Subscriber Line (ADSL), first tested at Bellcore in 1988, was designed to operate on existing lines already conditioned for BRI ISDN services, which itself is a switched digital service, though most incumbent local exchange carriers or ILECs provision Rate-Adaptive Digital Subscriber Line or RADSL to work on virtually any available copper pair facility whether conditioned for BRI or not.

The development of DSL, like many other forms of communication, can be traced back to Claude Shannon's seminal 1948 paper: A Mathematical Theory of Communication. Employees at Bellcore developed ADSL in 1988 by placing wide-band digital signals above the existing baseband analog voice signal carried between telephone company central offices and customers on conventional twisted pair cabling facilities.

Contrary to its name, while a DSL circuit provides digital service, it is actually not a digital signal. The underlying technology of transport across DSL facilities uses high-frequency sinusoidal carrier wave modulation, which is an analog signal transmission. A DSL circuit terminates at each end in a modem which modulates patterns of bits into certain high-frequency impulses for transmission to the opposing modem. Signals received from the far-end modem are demodulated to yield a corresponding bit pattern that the modem retransmits, in digital form, to its interfaced equipment, such as a computer, router, switch, etc. Unlike traditional dial-up modems, which modulate bits into signals in the 300–3400 Hz baseband (voice service), DSL modems modulate frequencies from 4000 Hz to as high as 4 MHz. This frequency band separation enables DSL service and plain old telephone service (POTS) to coexist on the same copper pair facility. Generally, higher bit rate transmissions require a wider frequency band, though the ratio of bit rate to bandwidth are not linear due to significant innovations in digital signal processing and digital modulation methods.

Early DSL service required a dedicated dry loop, but when the U.S. Federal Communications Commission (FCC) required ILECs to lease their lines to competing DSL service providers, shared-line DSL became available. Also known as DSL over Unbundled Network Element, this unbundling of services allows a single subscriber to receive two separate services from two separate providers on one cable pair. The DSL service provider's equipment is collocated in the same central office as that of the ILEC supplying the customer's pre-existing voice service. The subscriber's circuit is then rewired to interface with hardware supplied by the ILEC which combines a DSL frequency and POTS frequency on a signal copper pair facility.

On the subscriber's end of the circuit, inline low-pass DSL filters (splitters) are installed on each telephone to filter the high-frequency "hiss" that would otherwise be heard. Conversely, high-pass filters already incorporated in the circuitry of DSL modems filter out voice frequencies. Although ADSL and RADSL modulation do not use the voice-frequency band, nonlinear elements in the phone could otherwise generate audible intermodulation and may impair the operation of the data modem in the absence of low-pass filters.

Older ADSL standards can deliver 8 Mbit/s to the customer over about 2 km (1·25 miles) of unshielded twisted-pair copper wire. As of 2009, the latest standard, ADSL2+, can deliver up to 24 Mbit/s, depending on the distance from the DSLAM. Distances greater than 2 km (1.25 miles) significantly reduce the bandwidth usable on the wires, thus reducing the data rate. ADSL loop extenders increase these distances substantially.

            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 travellers. 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 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 (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 prevent hogging of access, 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 American adults still use dial-up Internet access. Reasons for retaining dial-up access span from lack of infrastructure to 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.