CHAPTER 4

Protocols

A protocol is an agreement on how something is done. There are many types of protocols. There are business protocols that define how business is properly carried out and social protocols that define what type of behavior is acceptable. Networking protocols define the rules of communication between devices.

It is possible for computers to be enabled for more than one networking protocol at a time, but to interact with another computer, both devices must share at least one networking protocol. In this respect, protocols are like languages. If both devices don't speak a common language, they can't communicate.

In this chapter, protocols at every layer of the TCP/IP model are discussed. Some of these are networking protocols and some are special function protocols, such as SMTP, which transfers emails. As you have learned, routing is the process of determining the best route to a packet's destination. This best route can be configured manually on the router (called static routing), or the router can be configured to use a routing protocol, which dynamically learns the routes. There is also a routed protocol, which is a networking protocol such as TCP/IP, that can be routed, but it does not perform the routing. Routing and routed protocols are compared and contrasted in this chapter as well. Specifically, this chapter covers the following topics:

• Understanding the function of protocols
• Exploring Application layer protocols
• Exploring Transport layer protocols
• Exploring Internet layer protocols
• Exploring Network Access layer protocols