Network Security Bible, 2nd Edition

Chapter 15. Network Protocols

IN THIS CHAPTER

• Reviewing the need for protocols

• Understanding the seven-layer OSI model

• Understanding the TCP/IP protocol

• Discussing address resolution

For entities to communicate, they must agree upon a message format and define common practices for exchanging these messages. Computers and networks are no exception.

This chapter introduces layered communication models and explains the principal protocols used under these models for communication among computers.

Protocols

The word protocol has a number of definitions, based on the context of its use, but in general protocols are rules of communication. In diplomacy, for example, a protocol can mean an agreement incorporating the results of a particular stage of a negotiation. For two or more people to communicate, they need to use a common language, such as English. The language is the protocol, or series of constructs, that enables people to form words from sounds, and then use words to create sentences. If constructed correctly the sentences create some meaning, as defined by the protocol. In the area of computer communications, a protocol is a formal set of rules that describe how computers transmit data and communicate across a network. The protocol defines the message format and the rules for exchanging the messages. This allows a computer to receive a series of 1s and 0s and to be able to interpret them into something meaningful.

Because of the complexity and multiple functions required to initiate, ...