Data communication protocols

A protocol therefore describes the syntax, semantics, and synchronization of communication. A programming language describes the same for computations, so there is a close analogy between protocols and programming languages: protocols are to communications what programming languages are to computations. (A less technical reader might appreciate this similar analogy: protocols are to communications what grammar is to writing.)

Diplomatic documents build on each other, thus creating document-trees. The way the sub-documents making up a document-tree are written has an impact on the complexity of the tree. By imposing a development model on the documents, overall readability can be improved and complexity can be reduced.

An effective model to this end is the layering scheme or model. In a layering scheme the documents making up the tree are thought to belong to classes, called layers. The distance of a sub-document to its root-document is called its level. The level of a sub-document determines the class it belongs to. The sub-documents belonging to a class all provide similar functionality and, when form follows function, have similar form.

The communications protocols in use on the Internet are designed to function in very complex and diverse settings, so they tend to be very complex. Unreliable transmission links add to this by making even basic requirements of protocols harder to achieve.

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