The Internet
Concatenation of many individual, campus, state region and national network into one single network all sharing a common addressing scheme. The Internet is often referred to as the information super highway or cyberspace.
Intranet Definition
An Intranet is a network based on the internet TCP/IP open standard. An intranet belongs to an organization, and is designed to be accessible only by the organization's members, employees, or others with authorization. An intranet's Web site looks and act just like other Web sites, but has a firewall surrounding it to fend off unauthorized users. Intranets are used to share information. Secure intranets are much less expensive to build and manage than private, proprietary-standard networks.
Extranet Definition
Extranet refers to a group of websites, belonging to independent entities that are combined together in order to share information. This is in contrast to an intranet, which is a private site that is only accessible for employees of an entity. Extranets are used in the supply chains to allow for more effective communications along the supply chain. They are replacing proprietary standard networks that are considerably more expensive to establish, and therefore were only used by large organizations.
Connection Categories
Connections to the Internet can be described in four basic categories: dialup, proxy, direct and leased.
A dialup connection is attained through a modem or similar device. The connection typically provides between 2400 bps (bits per second) and 28,800 bps throughput, which is usually more than adequate for e-mail and for running processes on the remote host. While this type of connection is usually adequate for line-oriented access, it is not suitable for full-screen programs. For instance, utilities such as Mosaic expect to be able to address the full screen of a machine that is directly connected to the internet. To make full use of many of the current Internet resources, then, a more advanced connection is required—at minimum, a proxy connection.
A proxy connection is also typically made through a modem, but it has special provisions that enable full Internet access. SLIP (Serial Line IP) and PPP (Point-to-Point Protocol) are two examples of such provisions .Tools such as FTP, Gopher are thereby available for use just as if the connection were directly on the Internet.
Direct connections are obtained when the machine being used has a dedicated circuit to the Internet. This can still be a remote connection, but it has the full functionality of a directly connected machine. A good example is ISDN (Integrated Services Digital Network), which is discussed later in this chapter.
Lastly, the leased line is a circuit leased from the local telephone company that provides a permanent address on the Internet. The advantage of a permanent address is that it that enables services such as FTP or Gopher to be set up. The leased line varies in throughput from 9600 bps to 45,000,000 bps (45 Mbps).