The document that you are reading uses the terms network and networking throughout. Therefore, it is important that we share a common definition and understanding of what is meant by these words.
What Is a Network?
"Network" is a very old word referring to a web of interconnected ropes. Its use has been extended to describe a wide variety of interconnected entities such as a network of roads or even a network of friends. Most recently, the term network has been applied to a collection of computers interconnected so that they can communicate among one another. A somewhat more technical definition of a network is as follows:
NETWORK:
A shared communications system supporting digital communication
among attached computers.
Figures (PDF; 36.8KB; 3pp.)
Figure 1-1 illustrates a network user's view of the communications system. Although this illustration in extremely simple, a modern data communications network is a complex system of communications media and electronic equipment that transports digital information from one place to another. The scope of a network can be as small as several computers in a room or as large as millions of computers all over the world -- or both.
A small network serving a collection of computers in the same general location is referred to as a local area network or LAN. If the computers are more dispersed, for example in different buildings around a city or state, the network is referred to as a wide area network or WAN. Internetworking describes a model in which LANs are interconnected, often by means of WANs.
It is important to note that the definition of a network used in this document does not include any particular function or application. A network is the utility that enables communication -- much like the telephone system. If a network is designed properly, it can support many kinds of applications, and these applications can change and grow over time.
What Can Be Done by Using a Network?
Computer networks were first developed in the 1960's when there came to be more than a few computers in the world. Computer users at that time who wished to share data or computer programs were required to copy their information onto computer tape or other machine-readable media, then send that media via postal mail to their colleagues. This process took considerable time and expense, especially if information had to be sent to several individuals or the process had to be repeated frequently. Computer users felt it would be useful if they could send data directly from one computer to another electronically. Thus were planted the seeds of computer networking.
Today, there are millions of computers in the world and computer networks support a wide variety of applications, many of which are described in detail later in this document. Common application areas include:
- Person to person message systems such as electronic mail, electronic bulletin boards, and "chat" systems,
- Transfer of large blocks of data from computer to computer,
- Access to specialized or expensive computing machinery such as supercomputers,
- Access to information resources that are maintained at remote locations or are too large to be stored on personal computers,
- Sharing of expensive resources, such as color printers or scanners,
- Limited forms of audio and video conferencing.
Not all networks support all of these capabilities. However, the network technology that is described in this document was chosen partly because it does, and it can be adapted to new areas as well.
What Are the Elements of a Computer Network?
Networks are comprised of many elements, all of which must be designed to work together to form a reliable communications system. A typical network system can be divided into 3 main types of components: the physical media, active electronic components, and the network protocols. In general, each of these elements can be defined separately and can be made to work together. However, the most critical choice to be made in designing a data communications network is the choice of network protocols.
A protocol is an agreed-upon set of procedures intended to describe how 2 or more entities interact to achieve a goal. A computer network protocol is a detailed definition of how 2 or more computers exchange information in a way that all can understand. Thus it is really the network protocols that define a shared communications system supporting digital communication among attached computers.
In order to help our understanding of network protocols, the International Standards Organization (ISO) has defined a conceptual model, often referred to as "the seven-layer model" for computer networking as represented in Figure 1-2. This model separates the data communication aspects of networking from the particular applications that such communications might support. The critical set of protocols for the purposes of this document are those that support basic data transmission among computers over local and wide area networks.
7
Application/User
6
Presentation
5
Session Control
4
Transport Control
3
Network Control
2
Data Link Control
1
Physical Link Control
Figure 1-2
The ISO model uses a layered approach, each layer representing
a component of the total process of communicating.
Of course, a particular set of computers may understand more than one protocol for data transmission. Just as people have different languages, different protocols have been defined to support basic data transmission for particular applications and products. However, if we want to send a letter to a person in another country, the post office will use a common convention for transporting that parcel internationally. Whereas on the local level we may use many different "protocols" for communicating, when we want to communicate broadly we must rely on a more limited but commonly understood set of protocols. This is the basis on which the world wide "network of networks" known as the Internet has been built.
What Is the Internet?
The Internet is a vast and rapidly growing collection of interconnected networks that all support a common set of data communication protocols. The most commonly known of these protocols are the Transmission Control Protocol (TCP) and the Internet Protocol (IP), which together are referred to as "TCP/IP." Thus the Internet is often referred to as a TCP/IP network.
The Internet began as a federally funded experiment through the Defense Advanced Research Projects Agency (DARPA). It quickly became known as the ARPANET. By the late 1970's many government research labs and universities across the nation had received DARPA grants to work on communications and/or computing problems. These institutions began building local area networks on their campuses and connecting them into the ARPANET so that they could share information and resources with one another. The impact of this widespread development of networking was the refinement of new protocols and network applications.
By the mid 1980's, the success of the ARPANET overwhelmed its limited capacity. Recognizing the potential of networks to enhance the value of many of its grant programs, in particular the supercomputer center initiatives, the National Science Foundation (NSF) funded a new "national network infrastructure" in support of all national education and research goals. The backbone of this infrastructure, known as the NSFNET, replaced the ARPANET and greatly enhanced the capacity and scope of network connectivity.
The NSFNET architecture required the development of regional networks to serve as distribution systems within specific areas of the country. Initially NSF provided seed funding to start 13 regional networks, including 2 in California: the Bay Area Regional Research Network (BARRNet) in the north, and the California Education and Research Federation Network (CERFnet) in the south.
Today there are many regional and state networks as well as several commercial national network service providers. The non-government funded service providers support commercial use of their networks which has led to a large number of such networks joining the Internet infrastructure. Many international links exist as well, connecting networks in Europe, Asia, South and Central America, and Africa.
How Do We Create a Network for Our School System?
This is the question to which the rest of this document is devoted. This guide does not provide a blueprint for you, nor would that be practical since there are so many differences among your schools and districts. What this document does provide is a framework of essential information within which you will be able to build a plan that meets the unique needs of your site(s) while remaining compatible to those standards and protocols already established by the state and the nation.
