III. Dialup to an Internet Host
We turn next to a stage of connectivity in which you have an account on a machine directly connected to the Internet. Since no gateway separates you from the rest of the Internet, this stage of connectivity allows you to reach the majority of resources on the network. In the present section, we presume that access to your account is obtained via a dialup telephone link. As we shall see, this limits the convenience with which you can view some of the resources on the Internet.
The term Internet refers to all those interconnected computer networks which use a common data transport protocol (called simply the Internet Protocol or IP) and can communicate seamlessly with each other. The structure of the Internet will be discussed in more detail in the sections which follow. None of the bulletin board systems that discussed in the previous section are a part of the Internet, although they may be able (as are America Online, Compuserve and Prodigy) to pass electronic mail through a gateway to the Internet.
While the costs associated with the use of isolated bulletin boards are typically low (at least for individual access), there are many limitations to their use. Since, by definition, these services lack full connectivity to the Internet, they are isolated from many new developments on the larger networks. Many of the new services under development on the Internet are based upon what is known as the client/server model of computing. Information servers on the network manage various repositories of information. Access to this information is obtained by running a client program on some other machine on the network - either your own personal computer or some machine to which you have access.
Most client/server resources on the Internet are built upon the exchange of packets of information with a structure defined by the Internet Protocol. Each packet contains a certain amount of information to be transmitted, along with address information indicating the packet's origin and destination. In the client/server paradigm, the client and server machines exchange packets to conduct the basic transactions of information access. Since isolated bulletin boards can't access these packets, you typically can't access these services through such bulletin boards. This means that, while bulletin boards may provide a good introduction to the technology of electronic mail and on-line discussion groups, they may not provide an adequate upgrade path to new network services. The next stage of connectivity that we will discuss is one that does allow access to these resources.
The simplest means of access to client/server resources is by dialup to a remote host that is directly connected to the Internet. Many teachers already enjoy such access, since this is the level of connectivity that is provided by most universities for their students, faculty and staff, and it is therefore the level of service typically extended by these organizations for guest accounts in their community.
In addition to guest accounts on university systems, many teachers have network access through commercial services which implement this stage of connectivity. Familiar examples of commercial offerings of this type are Delphi and NETCOM. These particular companies offer service on the national level, but there are dozens of similar local services.
Another route to this stage of connectivity is through one of the many Freenets under development. Most of these community-oriented services are based upon dialup access to an Internet host. The cost of operating such a system is not much different from the cost of operating an isolated bulletin board (the only added operational cost being that of network connectivity). Hence the fees for commercial systems of this sort are typically the same order of magnitude as the fees for the bulletin boards. The hardware and software requirements for people dialing to an Internet host are more or less the same as for dialing a bulletin board system. Hence this stage of connectivity allows for the same degree of interoperability as with bulletin boards and entails similar costs for the user. Readers may consult the previous section for a detailed list of these costs.
Although people dialing to an Internet host can make use of many Internet services, they will still find some significant limitations with this type of service. The reason for these limitations is that while the host itself is connected to the Internet and can receive and process IP packets from services on the network, individual users cannot directly receive and process these packets. What this means is that services based upon the client/server paradigm can be accessed only through clients running on the host machine (to which the user's computer is making a dialup connection).
When you are restricted to use a client which is not running directly on your own computer, you cannot enjoy the full benefits of the client/server model. In particular, it is typically not possible to use a fully graphical interface with this level of connectivity. As a result the information resources on the network which provide graphics, sound and other multi-media components will be only partially accessible to people with dialup Internet access. Furthermore, the only clients available through such services are those which the service has chosen to offer. This may limit your access to some resources and the convenience of your access to others.
While this limitation may sound somewhat technical, it creates a fundamental problem for the end user. Without a full graphical interface any Internet resource appears one-dimensional and frankly old-fashioned. One should emphasize that this is not a limitation of the Internet itself, but of one mode of connectivity to the Internet. Because such a large fraction of teachers currently connected to the Internet have only this very limited mode of connectivity, there has grown up the misconception that the Internet itself is difficult to use, clumsy or old-fashioned looking. This suggests that the stage of connectivity corresponding to dialup to an Internet host is inadequate for wide-spread deployment in the schools.
In any case the model of dialup to Internet hosts scales poorly at the whole school level. One should not invest in hundreds of telephone lines for a school's data access. Rather one should develop networks within the school, which link computing devices in the school and provide access to external resources through a shared external connection. These local networks are known as Local Area Networks or LANs. LAN connectivity will be discussed in Section V below. The key to the economies of LAN access has to do with the existence of a shared infrastructure. The Internet itself involves a massive shared infrastructure; this is the basis of its intrinsic low cost.
Schools whose teachers' first introduction to the network has come through guest accounts with dialup access have sometimes developed a distorted picture of the network. Given this introduction, it is natural to try to extrapolate to the idea that whole-school connectivity is simply a few phone lines away. As we will see in the discussions which follow, there are more elements which must be put into place to achieve whole-school connectivity, and modems in every classroom are certainly not the most economical path to whole-school connectivity. The reason again has to do with the idea of shared infrastructure. Individual modems and phone lines are not shared and create higher costs. Furthermore, the maximum bandwidth available to any one user is just the bandwidth of that user's modem. By creating a shared infrastructure one can afford to invest in a high-bandwidth link that can be shared by all people in the school. Not only are total costs reduced, but individuals then have access to higher peak bandwidth for their own use.