3.1.5 Need for standards
When two devices communicate across a network, they must first agree on a certain set of predetermined rules, or protocols. Protocols refer to the rules of communication that devices use and are specific to the characteristics of the conversation. In our day-to-day personal communication, the rules we use to communicate over one medium, like a telephone call, are not necessarily the same as the protocols for using another medium, such as sending a letter.
Protocols define the details of how messages are transmitted and received. Similar to how people use language to communicate, protocols contain rules for how devices communicate.
A group of inter-related protocols that are necessary to perform a communication function is called a protocol suite. Protocol suites help ensure interoperability between network devices. Individual protocols within a protocol suite may be vendor-specific and proprietary. Proprietary, in this context, means that one company or vendor controls the definition of the protocol and how it functions. Some proprietary protocols can be used by different organisations with permission from the owner. Others can only be implemented on equipment manufactured by the proprietary vendor.