What is this Communication protocol

The protocol are generally a part of communication software .they instruct computer system and various terminal deviece about how exact transmission of data can take place from one computer to another .it ensures an efficient and error free transmission by performing following function.
1.     Connection establishment
2.     Frame formatting
3.     Data routing
4.     Flow control and error control
5.     Data security
6.     Precedence and order of transmissions
7.     Addressing  
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