World Wide Web

The World Wide Web is a distributed application that enables to navigate through a set of hyper linked documents called web pages. Each web page may contain text, pictures, audio clips, video clips and possibly links. A link specifies either a location in the same document or another web page location and name. The location may be another file in the same computer or in another computer attached to the Internet. The size of the web page typically ranges from a few kilobytes to a few hundred kilobytes. If the link is a video clip or a large file, then the transfer may be of a few megabytes.

Cable TV

By using frequency division multiplexing this CATV network can also provide data, telephone, and compressed videophone services. Connecting this CATV network to the telephone and other wide area networks would allow a wide area multimedia network to be implemented. On such a network information could be transported locally by the CATV network and over long distances by ATM over the SDONET network of the telephone company. This fusion of the CATV and telephone networks will be facilitated by collaboration, of the kind indicated by AT and T’s acquisition of TCI and Media One.

ATM Network

ATM technology is capable of carrying a wide range of information transfers from e-mail to video conferences, with a range of quality of service that can match the user needs. ATM could provide the full range of services contemplated as offerings on the information superhighway. To implement such a network, network service providers would install high speed ATM access lines to users over optical fiber or ADSL subscriber loops. The ATM cells would e switched by high speed ATM switches in the backbone network. The result would be a universal network, built on sound theoretical principles.

The Internet

The Internet today comprises hundreds of thousands of local area networks LANs worldwide, interconnected by a backbone wide area network WAN. LANs typically operate at rates of 10 to 100 Mbps. Corporate data networks typically have a much smaller speed connection to the Internet backbone compared with the LAN speeds. This is appropriate because LANs support the high bit rate traffic between workstations and file servers within a single organization. The WAN on the other hand supports electronic mail and infrequent file transfers that can be accomplished with low speed connections.

Network externalities

Externalities provide a powerful incentive for inter networking. When two independent networks are interconnected, the value to the users of both networks increases. The extra sources needed to implement the inter connection are few if the two networks follow compatible standards. The combination of network scale economies which reduce per user benefits as the network grows creates positive feedback that can lead to an exponential growth in demand and supply of network services. Examples of this growth occurred in the demand for facsimile machines and Internet access.

Digitization

There are two aspects to digitization. First any information bearing signal can be represented by a binary string with an arbitrarily high degree of accuracy. Second It is much cheaper to store, copy, manipulate and transmit a digital signal than an analog signal, because advances in electronics have made digital circuits much more robust and cheaper than analog circuits. Because of these two aspects the overwhelming majority of today’s communication systems are digital.