Upon completion of this chapter, you will be able to answer the following questions:
- What are network communication protocols?
- What are network communication standards?
- What are the differences and similarities of the OSI and TCP/IP models?
- How do the OSI model‛s Layer 1 and Layer 2 function in an Ethernet network?
Key Terms
This chapter uses the following key terms. You can find the definitions in the Glossary.
Institute of Electrical and Electronic Engineers (IEEE) page 104
International Organization for Standardization (ISO) page 99
Internet Engineering Task Force (IETF) page 96
Request for Comments (RFC) page 96
Introduction (5.0.1)
When you talk with someone, you are communicating. When you mail a card to a relative, you are communicating. You probably don‛t think much about the rules of communication when you do these two things. But there are rules, and good communication happens only when all parties know and follow those rules. It is the same with devices on a network. This chapter explains the rules, which are called protocols, of network communication. When you understand the various protocols and how they work with other protocols, you not only will understand how networks and the Internet work but also be able to troubleshoot problems in your own network.
The Rules (5.1)
Before communicating with one another, individuals must use established rules or agreements to govern the conversation. Rules are also required for devices on a network to communicate.
The Three Elements (5.1.1)
The primary purpose of any network is to provide a method to communicate and share information. From the earliest primitive human societies to the most advanced technological societies of today, sharing information with others has been crucial for human advancement.
All communication begins with a message, or information, that must be sent from one individual or device to another. The methods used to send, receive, and interpret messages change over time as technology advances.
All communication methods have three elements in common. The first of these elements is the message source, or sender. Message sources are people or even electronic devices that need to communicate a message to other individuals or devices. The second element of communication is the destination, or receiver, of the message. The destination receives the message and interprets it. The third element is called a transmission medium, or channel. It provides the pathway over which the message can travel from source to destination.
For example, in Figure 5-1, two people can communicate face-to-face. Prior to communicating, they must agree on how to communicate. If the communication is using voice, they must first agree on the language. Next, when they have a message to share, they must be able to format that message in a way that is understandable. If someone uses the English language but poor sentence structure, the message can easily be misunderstood. Each of these tasks describes protocols that are used to accomplish communication.
Figure 5-1 Protocols for Face-to-Face Communications
Communication Protocols (5.1.2)
Communication in your daily life takes many forms and occurs in many environments. You have different expectations depending on whether you are chatting via the Internet or participating in a job interview. Each situation has its corresponding expected behaviors and styles.
Before beginning to communicate with each other, you establish rules or agreements to govern the conversation. These agreements include the following:
- What method of communication should you use? (See Figure 5-2.)
- What language should you use? (See Figure 5-3.)
- Do you need to confirm that your messages are received? (See Figure 5-4.)
Figure 5-2 shows two people agreeing on a method of communication.
Figure 5-2 Method of Communication
Figure 5-3 shows two people agreeing on a common language to use for communication.
Figure 5-3 Language Used for Communication
Figure 5-4 shows the communication between two people, including confirmation of the order.
Figure 5-4 Confirmation of Communication
These rules, or protocols, must be followed for the message to be successfully delivered and understood. Among the protocols that govern successful human communication are these:
- An identified sender and receiver
- Agreed-upon method of communicating (face-to-face, telephone, letter, photograph)
- Common language and grammar
- Speed and timing of delivery
- Confirmation or acknowledgment requirements
The techniques that are used in network communications share these fundamentals with human conversations.
Now think about the commonly accepted protocols for sending text messages to your friends.
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