Network access involves the act of one computer making use of the resources of another computer or group of computers. From the point of view of the user, one machine is local (functionally nearby) and the other is remote (reached by a more indirect means). You are usually using the local machine to call and control the remote machine. The remote machine is often referred to as the host because it usually contains the software that you want to use and thus acts as the host for your session. You can easily get confused about which machine is local or remote when using the Internet because you are often using more than two computers. Sometimes you access one host computer to use the software necessary to control a more remote one. When more than two computers are involved, everything becomes relative. You may need to differentiate between two hosts by referring to the closer one as the local host and calling the distant one the remote host. For the sake of clarity, this document will refer to the final host computer that contains the object of your search as the target hardware. Its programs and data are called the target software.
The physical connections between the machines involved in a network are called links. These can be either permanent or dial-up. Permanent connections involve direct wiring between the computers that is never disconnected. The wire might be owned by you, but it is more likely to be a leased line rented from a telephone company or other commercial carrier. Dial-up connections make use of switched links such as normal existing telephone system to allow one computer to dial-up the other each time a connection is desired. Early PC users connected to the Internet using the dial-up approach. Most now use permanent connections such as coaxial cable (TV), fiber-optic cable, or DSL (Digital Subscriber Lines). Typical telephone lines cannot reliably transmit the digital electrical signals used by computers, so signal translating devices called modems are used to convert the digital signals into the analog signals normally transmitted over phone lines and then back into digital form at the receiving end.
Permanent connections are more secure and reliable because they don't use switched links. A switched link, such as the telephone line coming to of your house, is less expensive but will require you to go through a series of steps to establish contact with the host computer whenever your local machine originates a session. Most data communications software can be configured to store the necessary information for contacting a particular host computer. A user can choose a specific host from a stored list of possible host machines. Then the data communications software will place the phone call and establish contact with the host computer.
Many offices and schools use networks known as Local Area Networks or LAN's. These are often connected to other networks by machines called routers or gateways that control the link and the transmission of data between the local network and the remote network. IRSC classrooms use LAN's.
Communication between two devices requires that both devices use a common language and procedural rules when sending data back and forth. Such standardized rules are referred to as rules of protocol. Both machines must agree on the data transmission speed (or baud rate). Both must agree on the data language(s) to be used. If your computer is acting as a terminal to another computer, the keyboard of your machine must be able to send the same codes that the remote host computer's keyboard would produce; otherwise, your keyboard will not be able to control the host. If the two keyboards are too different, then one of the two computers will have to translate the codes generated by the your keyboard into those expected by the host machine. This process of one device imitating another is referred to as emulation. Most good data communications software packages have the ability to perform some emulation functions. The most common emulation in use on the Internet is for an old standard computer terminal known by its model number VT100. Few of these are still in use, but they were so popular at one time that most hosts can recognize the language generated by them.
All networks must have well defined protocols in order for all of the separate devices, known as nodes, attached to the network to communicate with each other properly. Generally, the more complex the network, the more complex its protocols. The title "Internet" was actually a name invented to describe a sophisticated protocol that was developed to allow internetwork communication. A protocol known as the Internet Protocol or IP defined rules for organizing data into easily managed and transmitted packets of data. The standardized IP allowed many networks to share data and work cooperatively. Thus, the resulting super-network that IP allowed is referred to by the name The Internet. You will often find IP referred to in combination with another protocol known as Transmission Control Protocol or TCP which is used to group and route messages through networks. Together these are known as the TCP/IP suite.
Software that allows one computer to contact or control another is called communications software or remote access software. Two basic types of this software exist. One uses an approach called Terminal/Host access. The other uses the Client/Server approach to access.
The terminal/host approach is being used when a local computer calls a host and acts only as a distant terminal to it. All of the target software is running on the host computer. The local machine is simply acting as a data entry or retrieval device. The only software being used on the local computer is the data communications software that controls the local modem and dials the phone to originate the call. Most electronic bulletin board systems use terminal/host access. Your PC acts as a terminal and the remote computer system is the host. Under this approach, your PC does not need to contain any special software beyond its basic data communications software. The host contains all the software that is necessary. But because your PC is acting only as a terminal, the host does not expect it to have storage ability, so the host often re-transmits frequently used information such as menus, titles and lists. Thus, the terminal access approach generates very heavy network traffic (transmissions between the host and the local machine.)
The client/server access approach is more sophisticated and more powerful because the software that performs network functions is moved closer to the local user by dividing it into two parts: client software that runs on the local machine, and server software that runs on the remote host. Using this approach, much of the complex processing done to access network resources is done by the local machine. This approach reduces the amount of network traffic. The popular computer information service America Online® (AOL) uses the client/server access approach. AOL users are each given an AOL client program to run on their PC's. These clients communicate with server software running on the AOL host. Menus and other lengthy lists produced by AOL's host system are transmitted only once to each client program which then stores them on the user's PC and reuse them as necessary during a network session.
Most software that is used to manipulate the Internet uses the client/server access approach. This means that you must run client software on your PC in order to interact with server software on a target host. Client software can be purchased for most major hardware platforms, including machines running DOS, Windows, UNIX/Linux, and Apple brands of operating system. Many free or low cost versions of most clients can be found on Internet hosts and copied onto your PC. Public domain (unlicensed) software and freeware (licensed for free usage) are free. Shareware can be duplicated and evaluated for free, but you are expected to pay a registration fee if you plan to continue using it. When client software is run locally on your machine, the client is referred to as a local client and your link to the Internet is called a native connection because your computer is using TCP/IP protocol directly. In this case, your computer is called a peer on the Internet.
Most major commercial or academic computer networks are now attached to (thus a part of) the Internet. Many of us use such networks at work or at school daily. For us, there are no modems to use or phone lines to connect to. Our PC's are workstations attached to a network that is already a part of the Internet. Our PC's contain TCP/IP literate software that knows how to use our network connectivity to access other machines on the Internet. Often, we are protected from the rest of the Internet by computers (or software) called firewalls that monitor network traffic and block or pass data based on rules established by our network's administrator.
Rather than acquiring, installing and maintaining their own Internet client software, early users preferred to employ the terminal/host access approach. Using this approach, they would connect their PC's via non-Internet dial-up software to a local host (an intermediate computer) which contains the Internet client software necessary to contact and use desire target resources. They would then run the client software remotely on that host using their keyboard. (See the access diagram examples.) Client software that is run on an intermediate host through a dial-up connection is called a remote client. In this case, the PC does not run Internet protocol software locally and therefore is not an Internet peer. Instead, the local host is the peer. Both access approaches are in use simultaneously. The portion of the communication between the PC and the local host uses terminal/host access. The communication between the intermediate local host (running the Internet client software) and the target host (running the server software) uses Internet client/server access.
A PDF document has been stored containing three diagrams illustrating the different methods of Internet access. These are stored at
http://www.gibsonr.com/classes/internet/accessdiag.pdf
Although many computers are directly connected to the Internet through existing networks, what about the others? Who provides the connection to the Internet. Someone has to pay for all of these leased lines and phone charges. Most computer networks will not let you connect to them for free. They must also recoup operating costs. Therefore you must acquire an account with them for which you will usually be billed. Nobody gets an account on "the Internet"; rather you get an account on some network that is part of the Internet.
IRSC is a node on the Internet. Our college-wide system of networks know as the RiverNet is attached to the Internet. And since all IRSC campuses (Okeechobee, Saint Lucie West, Stuart, and Vero Beach) are connected to RiverNet, they are also connected to the Internet. Thus, most of our computer classrooms and labs have computers offering direct access to the Internet.
You can access the Internet through many sources. Some people connect to the Internet through on-line data companies (also known as information utilities) such as America Online® (AOL) or Earthlink®. Most of these companies started as resellers of data that they acquired through the Internet and other sources. Originally they did not offer direct access to the Internet. Rather, they used it as a data source, then reorganized that data into user-friendly menus for their subscribers. These services were easy to use because they provided all necessary software to connect to and use their systems and often included telephone support. But they also limited your access because they only gathered and offered the most popular data. Anyone who wants direct access to everything that the Internet has to offer should subscribe to an Internet Service Provider (ISP). Neither of these Internet access approaches are free. But the monthly charges are quite reasonable considering the benefits that you can derive from Internet access. ISP's are appearing and disappearing monthly, so you best practice to find one is to simply look in your local phone book or to do a search through one of the web-based lists of ISP's such as:
[http://www.all-free-isp.com]
[http://www.thelist.com]