Protocol

It is a language to transfer information  between two or more people / devices. A protocol is a set of mutually accepted rules that governs the communications between computers on a network.

A protocol defines

• What is communicated
• How it is communicated
• When it is communicated

In order for two People / Devices to talk to each other, they must be speaking the same language.they are needed for people / networks / computers / devices to understand each other.Different types of protocols are required to ensure reliable communication between devices.

Example: Ethernet, IP, TCP, HTTPs, SMTP, FTP

Communication tasks

We need to perform some tasks to establish a reliable and fast communication system.

Signal generation
Synchronization
Error detection and correction
Flow control
Addressing and routing
Security
etc

For communication to occur both ends (sender and receiver) must agree on a protocol

Basic elements of a protocol

• Syntax:

Syntax refers to the structure or format of the data, the order in which they are presented.Example, first 8 bit is sender address, next 8 bits are receiver address and remaining bits are data.

• Semantics:

Semantics refers to the meaning of each section of bits.For example, These bits identify the route to be taken or the final destination.Control information.

• Timing:

When and how fast the data can be sent.To avoid the overloading the receiver and data lost.

Steps to design a protocol

While designing a protocol, we need to consider the following basic factors.

• Choose the pattern of communication.(Client-server, Peer to peer, one to one, Multicast, broadcast)
• Design goals( Fast, reliable, security features and controlling)
• Message format ( binary structure, header and body part)
• Communication rules ( how communication start and stop)

Simple protocol

A simple protocol has following features

No security
No flow control
No acknowledgement
No error detection and control

Designed / written by using a programming language / Operating system.

Protocol Layering

Network designers organize protocols and the network hardware and software that implement the protocols in layers. each layer provides its services to another layer. Protocol and hardware layering is a conceptual structure As we have seen in OSI reference model. layering provides a structured way to discuss system components.

Suite of protocols

When taken together, the protocols of the various layers are called the protocol stack. We have an example of TCP/IP protocol suit / stack.IT consist of physical layer, Data link layer, network Layer, transport Layer.

OSI Layers.

In 1970,the open system interconnection (OSI) model was created by the International Organization for standardization (ISO).
It defines how data and Network information are communicated from one computer to another computer.
Each layer performs a well defined function.