March 2003
Intermediate to advanced
912 pages
27h 17m
English
A communications protocol is a set of rules for controlling communication. It may define a particular, ordered sequence of messages to be used in a communication. The order is agreed by convention between the communicating entities to satisfy their requirements. A simple example, taken from a different context, is:
| message: | 'Hi beta, this is alpha, are you receiving me? OVER' |
| reply: | 'Yes alpha, this is beta, I'm receiving you. OVER' |
The above two messages implement a connection establishment protocol.
An example of an application protocol (see Figure 3.16) is a client's interaction with a file server, for example:
| file-id = | open (filename, write-mode) |
| data-bytes = | read (file-id, byte-range) |
| close (file-id) |