The following is a summary of each topic in the chapter:
The Rules—All communication methods have three elements in common. The first is the message source, or sender. Message sources are people or electronic devices that need to communicate a message to other individuals or devices. The second is the destination, or receiver, of the message. The destination receives the message and interprets it. The third is the transmission medium, or channel. It provides the pathway over which the message can travel from source to destination.
Among the protocols that govern successful human communication are an identified sender and receiver, an agreed-upon method of communicating, common language and grammar, speed and timing of delivery, and confirmation or acknowledgment requirements. Networking protocols define the message format, message size, timing, encoding, and message patterns over the local network.
Communication Standards—Networking and Internet standards ensure that all devices connecting to the network implement the same set of rules or protocols in the same manner. Using standards, different types of devices are able to send information to each other over the Internet. These standards are developed, published, and maintained by a variety of organizations. When a new standard is proposed, each stage of the development and approval process is recorded in a numbered RFC document so that the evolution of the standard is tracked. RFCs for Internet standards are published and managed by the IETF.
Network Communication Models—A stack illustrates the protocols as a layered hierarchy, with each higher-level protocol depending on the services of the protocols shown in the lower levels. The separation of functions enables each layer in the stack to operate independently of others.
The layered model has many benefits:
Assists in protocol design, because protocols that operate at a specific layer have defined information that they act upon and a defined interface to the layers above and below
Fosters competition because products from different vendors can work together
Enables technology changes to occur at one level without affecting the other levels
Provides a common language to describe networking functions and capabilities
The suite of TCP/IP protocols used for Internet communications follows the structure of the stack model. The two basic types of models to describe the functions that must occur for network communications to be successful are protocol models and reference models. The most widely known internetwork reference model is the OSI model. The OSI model breaks down network communications into multiple processes. Each process is a small part of the larger task.
The protocols that make up the TCP/IP protocol suite can be described in terms of the OSI reference model. The functions that occur at the Internet layer in the TCP/IP model are contained in the network layer of the OSI model. The transport layer functionality is the same between both models. However, the network access layer and the application layer of the TCP/IP model are further divided in the OSI model to describe discrete functions that must occur at these layers.
Ethernet—There is no official LAN standard protocol, but over time, Ethernet has become more common than the others. Ethernet protocols define how data is formatted and how it is transmitted over the wired network. The Ethernet standards specify protocols that operate at Layer 1 and Layer 2 of the OSI model. Ethernet standards have evolved for specifying faster and more flexible versions of the technology. Each version of Ethernet has an associated standard. Each host connected to an Ethernet network is assigned a physical address that serves to identify the host on the network. Every Ethernet network interface has a physical address assigned to it when it is manufactured. This address is known as the MAC address. The MAC address identifies each source and destination host on the network.