What is an ISP ?

An ISP (Internet Service Provider) is a company that collects a monthly or yearly fee in exchange for providing the subscriber with Internet access.
An ISP might provide dial-up service, cable, DSL, or other types of Internet access. Some ISPs are local while others are national. A national ISP will provide access throughout most of the nation, while a local ISP will only serve subscribers in a limited geographical region.
When looking for an ISP the initial consideration is the type of access desired. Some ISPs only offer dial-up access which is the slowest type of connection. If you want cable service, you'll be checking with your local cable TV provider to see if cable access is offered. For DSL service, you may have multiple choices - or it could be that DSL is not yet available in your area. Often this can be remedied with a call to the phone company to upgrade local telephone lines.

Every ISP has a privacy policy and Terms of Service (TOS) contract that subscribers must agree to before subscription will be accepted. The privacy policy will state what the company will and will not do with personal information collected at the time of sign-up. Name, address, and normally a credit card number are required. The privacy policy should also state under what conditions your personal information might be shared with third parties, government officials, or others. The TOS contract stipulates how you can use the service. For example, dial-up access is often sold as "unlimited access" but this is not to be taken literally. Dial-up accounts normally limit hours per month to 250-400, depending on the ISP. Truly unlimited access (leaving your computer on and actively connected to the Internet 24/7) is called dedicated access. Most DSL or cable subscriptions allow dedicated access.
The Terms of Service contract of the ISP will also state rules about hacking, protecting copyrighted materials, denial of service attacks, harassing other people, spam, compromising the service, and many other issues. These are as much for the legal protection of the ISP as to let potential subscribers know what the ISP will and will not tolerate. If you are planning on using web space provided by the ISP, check for limitations here too. Many ISPs do not allow commercial websites to be set up on their servers. This usually means that nothing can be sold from your personal webspace, including for example, a software program you wrote, original music, or any other item. ISP websites are normally for personal use only, to blog, post pictures, and so on.
Once you find an ISP that offers the services, privacy policy and TOS you can live with, you can sign up online through a public terminal, or call. From here all that needs to be done is to enter the ISP access number and a few other parameters into the networking software on your computer.
ISP services range in price according to the package offered, and type of service. Dial-up is least expensive, and perks will vary greatly between ISPs. Some offer multiple email accounts, others vast amounts of webspace, and still others discounts for paying in advance. DSL and cable companies will also differ, so carefully read through offerings before deciding. If you are getting an ISP other than cable, you will likely have choices. There are many websites that offer reviews from present subscribers of various ISPs, which might be helpful in making a decision.

What Is DSL ?

DSL (Digital Subscriber Line) is a high-speed Internet service that competes with cable Internet to provide online access to local customers. It operates over standard copper telephone lines like dial-up service, but is many times faster than dial-up. In addition, unlike dial-up, DSL does not tie up the phone line. Coexisting with telephone service in this way allows users to surf the Net and use the phone at the same time.
The service requires a DSL modem, which connects to the telephone wall jack and computer. The device acts as a modulator, translating the computer’s digital signals into voltage sent across the telephone lines to a central hub known as a Digital Subscriber Line Access Multiplier (DSLAM, or dee-slam). In lay terms, the DSLAM acts as a switchboard for local DSL clients, routing requests and responses between each client’s computer address and the Internet.

 ADSL Filter.

Voice calls and DSL can coexist on copper lines because each service utilizes its own frequency band. The bands might be thought of like lanes of a freeway. Voice signals are sent in a relatively low band, while Internet signals occupy a much higher band. To keep the voice band clear of bleeding signal noise, a small filter is commonly installed on all telephone lines in the house, blocking the higher frequencies.

The DSL “service lane” is split for two-way traffic, or downstream and upstream signals. When you click on a link, you are requesting something from the Internet, initiating upstream traffic. The returned webpage arrives as downstream traffic. Since requests only require small bits of data, the upstream lane can be fairly narrow (low bandwidth), but the downstream lane must be much wider (high bandwidth) to send webpages, multimedia, graphics, files and programs. Thus, standard DSL is called Asynchronous DSL or ADSL, because the download speed is much faster than the upload speed.
Businesses, however, might require sending large files, data and programs between non-local networked offices, in which case a different type might be preferred. Synchronous DSL or SDSL offers the same high speed for both downloading and uploading. Hard core geeks might also like SDSL for exchanging files, games and other multimedia. The drawback is that it is more expensive than ADSL.
With today’s ubiquitous use of cell phone service, millions of people have foregone landline service all together. In this case a service known as “naked DSL” might be offered in an area, which provides Internet service without telephone service.
In many areas, fiber optic cable service (FiOS) is replacing standard telephone lines. FiOS provides much greater bandwidth than copper lines with the ability to offer true high-speed Internet that is many times faster than DSL or standard cable service. Though availability differs between regions, FiOS services typically offer bundled options for television, digital telephone and Internet.
Among the various DSL packages, plans are based on speed, with slower speeds costing less than plans that offer higher speeds. The distance to the nearest DSLAM will determine in large part the actual speeds the service achieve. The closer to the DSLAM the better, as the signal degrades with distance, causing latency issues. If a user is at the outskirts of the service area, he or she might not see the full speed of the subscribed plan.
A DSL modem is commonly included with service as a “leased” item to be returned at the end of the contract, but this is typically a standard modem without router or wireless capability. If a person wants to share the Internet connection with another computer in the home or office wirelessly, he or she will likely require an upgrade. In some cases, the cost of this upgrade in the DSL contract is equal to buying a wireless router with built-in modem. Subscribers should the fine print; if they will have to return the device at the end of the contract period, they might want to opt to supply their own equipment.