Articles: What is a protocol ?

What is a protocol ?

Posted on 10:40 AM, under Networks

Author: Youssef Sosso

Table of Contents

* What is a protocol?
* Protocols oriented and not connection-oriented
* Protocol and Implementation

What is a protocol?

A protocol is a standard that enables communication between processes (possibly running on different machines), that is to say a set of rules and procedures to be followed to make and receive data over a network. There are different depending on what is expected of communication. Some protocols are for example specialized in the exchange of files (FTP), others may simply be used to manage the state of the transmission and error (in the case of ICMP) ...

On the Internet, the protocols used are part of a suite of protocols, that is to say a set of protocols linked together. This protocol suite called [tcpip.php3 TCP / IP].
It contains, among others, the following protocols at different levels depending on the levels of the OSI:

* Layer 2 and off-ip:
o ARP
* Layer 3 Internet Protocol:
o IPV4
o IPV6
* IP Layer 4 Protocols
o ICMP
o TCP
o UDP
o ....
* Layer 7 Application layer protocols
o FTP
o HTTP
o SMTP
o Telnet
o NNTP ......

Oriented protocols, not connection-oriented

Protocols are generally classified into two categories depending on the level of control data that is to be:

* The connection-oriented protocols: These protocols operating control of data transmission over a communication established between two machines. in such a scheme, the receiving machine sends acknowledgments in communication, and the sending machine guarantees the validity of the data it sends. The data are sent as a stream. [Tcp.php3 TCP] is a connection-oriented protocol
* The connection-oriented protocols not: This is a mode of communication in which the sending machine sends data without notifying the receiving unit and the receiving unit receives the data without sending notice of receipt to the first. The data are sent in blocks (datagrams). [Udp.php3 UDP] is a connectionless orientated protocol

Protocol and implementation

A protocol defines only the way in which the machines have to communicate, that is to say, the form and sequence of data to be exchanged. A protocol does not define cons not how to program software so that it is compatible with the protocol. Called the translation and implementation of a protocol in computer language.

The protocol specifications are never complete, as it is common implementations are subject to some interpretation of specifications, which sometimes leads to some specific implementations or worse to incompatibilities or security flaws!