Before we can use the Internet, we have to gain access to it.  This access is achieved in one of several ways, which we will discuss in this How to Access the Internet article. Above all, the Internet is a collection of networks that are connected together through various protocols and hardware.

Dial-up Connection:

one of the commonest ways of connection to Internet is through dial up connection using a modem and a telephone line. Using these you can connect to a host machine on the Internet. Once connected the telecommunications software allows you to communicate with the Internet host. When the software runs it uses the modem to place a telephone call to a modem that connects to a computer attached to the Internet.

The SLIP (Serial Line Internet Protocol) or PPP (Point to Point Protocol):

Two protocols; serial line interface protocol (SLIP) and the point-to-point protocol (PPP), allow a user to dial into the Internet. They convert the normal telephone data stream into TCP/IP packets and send them to the network. With these, the user becomes a peer station on the Internet and has access to all of the Internet’s facilities.

Internet Service Providers

As mentioned earlier, nobody truly owns the Internet, but it is maintained by a group of volunteers interested in supporting this mode of information interchange.  Central to this control is the Internet service provider (ISP) which is an important component in the Internet system. Each ISP is a network of routers and communication links.  The different ISP's provide a variety of different types of network access to the end systems, including 56 Kbps dial-up modem access, residential broadband access such as cable modem or DSL, high-speed LAN access, and wireless access.  ISP's also provide Internet access to content providers, connecting Web sites directly to the Internet. To allow communication among Internet users and to allow users to access worldwide Internet content, these lower-tier ISP's are interconnected through national and international upper-tier ISP's, such as Sprint.  An upper-tier ISP consists of high-speed routers interconnected with high-speed fiber-optic links.  Each ISP network, whether upper-tier or lower-tier, is managed independently, runs the IP protocol (see below), and conforms to certain naming and address conventions.

ISDN (Integrated Services Digital Network) Service

The whole idea of ISDN is to digitize the telephone network to permit the transmission of audio, video and text over existing telephone lines.  The purpose of the ISDN is to provide fully integrated digital services to users.

The use of ISDN for accessing the Internet has breathed new life into the ISDN service. ISDN’s slow acceptance was due mostly to a lack of a need for its capabilities. Being a digital interface, ISDN has provided a means for accessing web sites quickly and efficiently.  In response to this new demand, telephone companies are rapidly adding ISDN services.

The ISDN standard defines three channels types, each with the different transmission rate: bearer channel (B), data channel (D) and hybrid channel (H). The B channel is defined at a rate of 64 Kbps.  It is the basic user channel and can carry any type of digital information in full duplex mode as long as the required transmission does not exceed 64 kbps.  A data channel can be either 16 or 64 kbps depending on the needs of the user used to carry control signals for B channels. Of the two basic rate B channels, one is used to upload data to the Internet and one to download from the Internet.
 
The D Channel assists in setting up connection and maintaining flow control. There are three ways ISDN can be used to interface to the Internet, by using a modem, adapter, or bridge/router.  ISDN modems and adapters limit access to a single user.  Both terminate the line into an ISDN service.  The difference between them is that the ISDN modem takes the Internet traffic and pushes it through the computer serial port, while, the faster ISDN adapter connects directly to the computer’s buses. 

ISDN bridge/routers allow for local network connections to be made through ISDN to the Internet.  The ISDN termination is made into an Ethernet-type LAN so that multiple users can achieve access to the Net through a single access address.  Transfer rates between user and the Internet are between 56 and 128 Kbps.

Direct ISP Service through Leased Line

The most costly method of accessing the Internet is to use leased lines that connect directly to the ISP.  This will increase access rate to anywhere between 64 K and 1.5 Mbps, depending on the system in use.  Equipment called data service units (DSU) and channel service units (CSU) are set up in pairs, one pair at the customer site and the other at the ISP site. There is no phone dialing required since the connection is direct. Also the only protocol needed to complete the access is TCP/IP, for much the same reason. Depending on the transfer rate required and the distance between the sites, cabling between them can be made with fiber optic cables or unshielded twisted-pair (UTP) copper wire.

Cable Modem 

One more way of accessing the Internet currently being developed is the use of cable modems.  These require that you subscribe to a cable service and allow you two-way communication with the Internet at rates between 100K and 30 Mbps.  The cable modem performs modulation and demodulation like any other modem, but it also has a tuner and filters to isolate the Internet signal from other cable signals.  Part of the concern for use of the cable modem is to formulate LAN adapters to allow multiple users to access the Internet.  A medium access control (MAC) standard for sending data over cable is being formulated by the IEEE 802.14 committee.