5.3.2 Peer-to-Peer Connectivity

Peer-to-peer networks are an alternative to the client-server framework. Instead of having a central server that all clients communicate with, every member of a peer-to-peer network can communicate with any other member. One example is a multi-player network game, where each player's computer talks directly with all the others to transmit moves and update the state of the "world." Only some games are organized this way. Others rely on a server.

Another example of a peer-to-peer network was Napster, the controversial system for sharing music over the web. (Napster was controversial because many of the songs people wished to share were copyrighted.) Each user running a Napster client could communicate directly with any other user to send or receive a particular song. However, in order for users to find each other, Napster relied on a central server to keep track of which songs each user was offering to share. Hence, Napster was a hybrid system. The central directory provided for efficient indexing and search functions so users could quickly find the material they wanted. But, the actual file sharing took place via the direct peer-to-peer network, eliminating the server as a potential communications bottleneck.

The use of a central server was viewed as a vulnerability of Napster, since if the server was attacked, or shut down by a court order, the service could not function. For this reason, newer file sharing programs such as Gnutella and FreeNet were developed that are purely peer-to-peer, and that hide the identities of machines sharing information over the network. These programs had uses other than violating copyrights on music: they provided a press that could not be censored, which was important for people in countries without strong protection of free speech.

5.4 Data Transfer Technologies

The process of transferring data between two computers is known as data communications. Two critical decisions must be made for computers to communicate through a network: the protocol (rules for interpreting the data stream), and the communications medium (cable, optical fiber, or wireless methods using radio signals.)

Reading Sequence: Parsons/Oja, Chapter 6-Section A. Learning Goal: Knowledge of communication signals, topologies, and different protocols that are used to support data communications. Parsons/Oja, Chapter 6-Sections B and C. Learning Goal: Knowledge of the various types of Internet access including methods of connecting.

       

Assessments: Multiple-Choice Quiz 20

5.5 Internet Architecture

In this section, we will cover some of the details of how the Internet works.

Reading Sequence: 5.5.1 Routers and TCP/IP. Learning Goal: Knowledge about the TCP/IP protocol used to route and exchange data between computers on the Internet. 5.5.2 Domain Name Service. Learning Goal: Knowledge of how domain names are resolved to IP addresses for routing messages on the Internet. 5.5.3 Connectivity. Learning Goal: Knowledge of the types of network connectivity available to consumers and business owners. 5.5.4 Internet Service Providers. Learning Goal: Knowledge of the types of Internet Service Providers (ISPs) that are available and their role in connecting a computer system to the Internet.

          

Assessments: Multiple-Choice Quiz 21