Internet service provider (abbr. ISP, also called Internet access provider orIAP) is a business or organization that sells to consumers access to the Internet and related services. In the past, most ISPs were run by the phone company. Now, ISPs can be started by just about any individual or group with sufficient money and expertise. In addition to Internet access via various technologies such as dial-upandDSL, they may provide a combination of services including Internet transit,domain nameregistration and hosting, web hosting, andcolocation. Contents [ hide] • 1 ISP conne ction options • 2 How ISPs connect to the Interne t • 3 Vir tua l ISP • 4 Rela ted serv ice s • 5 See als o [edit] ISP connection options ISPs employ a range of technologies to enab le customers to connect to their network. For"home users", the most popular options include dial-up,DSL (typically ADSL), Broadband wireless access ,Cable modem, and ISDN (typically BRI ). For customers who have more demanding requirements, such as medium-to-large businesses, or other ISPs, DSL (often SHDSL), Ethernet, Metro Ethernet, Gigabit Ethernet, Frame Relay, ISDN (BRI orPRI), ATM,satellite internet access and SONET are more likely. With the increasing popularity of downloading music and online video and the general demand for faster page loads, higher bandwidth connections are becoming more popular. [edit] How ISPs connect to the Internet Just as their customers pay them for Internet access, ISPs themselves pay upstream ISPs for Internet access. In the simplest case, a single connection is established to an upstream ISP using one of the technologies described earlier in this article, and the ISP uses this connection to send or receive any data to or from parts of the Internet beyond its own
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network; in turn, the upstream ISP uses its own upstream connections, or connections to
its other customers to allow the data to travel from source to destination.
In reality, the situation is often more complicated. For example, ISPs with more than one
Point of Presence (PoP) may have separate connections to an upstream ISP at multiplePoPs, or they may be customers of multiple upstream ISPs and have connections to each
one at one or more of their PoPs. ISPs may engage in peering, where multiple ISPs
interconnect with one another at a "peering point" or "Internet exchange" (IX), allowing
the routing of data between their networks, without charging one another for that data -
data that would otherwise have passed through their upstream ISPs, incurring charges
from the upstream ISP. ISPs who require no upstream, and have only customers and/or
peers, are called Tier 1 ISPs, indicating their status as ISPs at the top of the Internet
hierarchy. Routers, switches, Internet routing protocols, and the expertise of network
administrators all have a role to play in ensuring that data follows the best available route
and that ISPs can "see" one another on the Internet.
[edit] Virtual ISP
virtual ISP (virtual Internet service provider, sometimes abbreviated as VISP or
vISP ) is a company that offers Internet services under its own company or
brand name, while actually using the equipment and facilities of another ISP
to provide those services. A virtual ISP typically offers the all same services as
a regular ISP, such as Web hosting, e-mail, newsgroup access, domain name
provision, and support. A number of real ISPs specialize in providing a virtual
ISP setup on a local or wider geographic basis. In some cases, the ISP offering
the virtual ISP setup can also handle billing and answer support calls for the
virtual ISP company under the virtual ISP name.
A Virtual ISP (vISP) purchases services from another ISP (sometimes called a wholesaleISP or similar within this context) that allow the vISP's customers to access the Internet
via one or more Points of Prescence (PoPs) that are owned and operated by the wholesale
ISP. There are various models for the delivery of this type of service, for example, the
wholesale ISP could provide network access to end users via its dial-up modem PoPs or
DSLAMs(Digital Subscriber Line Access Multiplexer (DSLAM) is a network device,
Refers to connecting a device to a network via a modem and a public telephone network.
Dial-up access is really just like a phone connection, except that the parties at the two ends
are computer devices rather than people. Because dial-up access uses normal telephone
lines, the quality of the connection is not always good and data rates are limited. In the past,
the maximum data rate with dial-up access was 56 Kbps (56,000 bits per second), but new
An alternative way to connect two computers is through a leased line, which is a permanent
connection between two devices. Leased lines provide faster throughput and better
quality connections, but they are also more expensive.
Dial-up access is a form of data access (mainly used for Internet access) in which the
client uses a modem to connect a computer to a telephone line and dials into an Internetservice provider 's (ISP) node to establish a modem-to-modem link, which is then routed
to the Internet.
Modern dial-up modems typically have a maximum theoretical speed of 56 kbit/s
WIRELESS BROADBAND
Broadband wireless access is a technology aimed at providing high-speed wireless
access over a wide area from devices such as personal computers to data networks.According to the 802.16-2004 standard, broadband means 'having instantaneous
• You can leave your Internet connection open and still use the phone line for voice calls.
• The speed is much higher than a regular modem
• DSL doesn't necessarily require new wiring; it can use the phone line you already have.
• The company that offers DSL will usually provide the modem as part of the installation.
Other types of DSL include:
• Very high bit-rate DSL (VDSL) - This is a fast connection, but works only over a short distance.
• Symmetric DSL (SDSL) - This connection, used mainly by small businesses, doesn't allow you to use the
phone at the same time, but the speed of receiving and sending data is the same.
• Rate-adaptive DSL (RADSL) - This is a variation of ADSL, but the modem can adjust the speed of the
connection depending on the length and quality of the line.
If you have read How Telephones Work, then you know that a standard telephone installation in the United Statesconsists of a pair of copper wires that the phone company installs in your home. The copper wires have lots of room for carrying more than your phone conversations -- they are capable of handling a much greater bandwidth, or range of frequencies, than that demanded for voice. DSL exploits this "extra capacity" to carry information on the wire withoutdisturbing the line's ability to carry conversations. The entire plan is based on matching particular frequencies to specifictasks.
To understand DSL, you first need to know a couple of things about a normal telephone line -- the kind that telephoneprofessionals call POTS, for Plain Old Telephone Service. One of the ways that POTS makes the most of the telephonecompany's wires and equipment is by limiting the frequencies that the switches, telephones and other equipment willcarry. Human voices, speaking in normal conversational tones, can be carried in a frequency range of 0 to 3,400 Hertz(cycles per second -- see How Telephones Work for a great demonstration of this). This range of frequencies is tiny. For example, compare this to the range of most stereo speakers, which cover from roughly 20 Hertz to 20,000 Hertz. And thewires themselves have the potential to handle frequencies up to several million Hertz in most cases.
worldwide for provisioning ofservices like voice, data and transmission over the teleph
through the telephone netwobeing viewed as the logical e
digitalization of telecommuniand most developed countrie
different stages of implemen
An ISDN subscriber can establish two simultaneous independent calls (except when the termina
such that it occupies two 'B' channels for one call itself like in video conferencing etc.) on existinthe telephone line (Basic rate ISDN) where as only one call is possible at present on the analog connection. The two simultaneous calls in ISDN can be of any type like speech, data, image etc.
time for a call between two ISDN subscribers is very short, of the order of 1 to 2 seconds. ISDN whole new set of additional facilities, called Supplementary Services.
ISDN- ISDN generally comes in two flavors, 64 Kbps and 128 Kbps.
DSL- DSL is a scalable technology, with speeds ranging from 128Kbps to 1.5 Mbps
Second, ISDN can be more expensive than DSL
DSL utilizes the standard copper wiring already installed into businesses and homes,requiring no special line installation for service
ISDN utilizes copper wiring as well, but a special ISDN line must be installed at thecustomer’s location.
Then ISDN connection charges vary, depending upon whether or not the customerrequires a dedicated, “always on” connection. Dedicated connections can get priceyas many ISDN packages are billed at a per-minute cost.
Special “dial-up ISDN” packages are available in most areas at a much lower cost and
can be a reasonable alternative in areas where DSL is not yet available
many DSL customers had problems with “cross-talk
And DSL still suffers from a distance limitation
In order to receive Asynchronous DSL (ADSL) service, a customer’s location must bewithin 18,000 feet (3 miles) of a central office (CO) of their local telephone serviceprovider