All machine-base communications must follow certain set of rules for exchange of data between nodes connected to a network. The rules to send and receive data are called protocols. These rules are defined in the network software. A protocol defines;
- Which is communicated?
- How it is communicated?
- When it is communicated?
Elements of Protocol
The key elements of protocol are described below.
1. Syntax
Syntax refers to the format or structure of data. The protocol accepts the data according to the predefined format. For example, a protocol may expect the format of data as;
- First 8-bits of the stream to be the address of header.
- Second 8-bits of the stream to be the address of receiver.
- Rest of the stream to be the actual data.
2. Semantics
Semantic means meaning. Semantics refers to the meaning of each section of the bits stream. It includes: how is a particular pattern of bits to be interpreted, and what action is to be taken based on that interpretation.
3. Timing
Timing refers to:
- When data should be sent?
- How fast it can be sent?
Functions of Communication Protocol
The data transmission software or protocols perform the following functions for the efficient and error free transmission of data.
Data Sequencing - The function of a protocol to divide the long message into smaller packets of fixed size that are to be transmitted for error free data transmission, called Data Sequencing.
Data Routing - The function of a protocol to find the most efficient path or route between the sender and the receiver before sending the data is called Data Routing.
Flow Control - The function of a protocol to control the rate of data transmission from the sender to the receiver is called Flow Control. It regulates the process of sending data between fast sender and slow receiver.
Error Control - The function of a protocol to detect and recover errors for successful data communication between the sender and the receiver is called Error Control. Successful data communication means that data is transmitted without any error.
Important Communication Protocols
The most common and popular communication protocols are:
1. Ethernet
2. Token Ring
3. TCP/IP Protocol
4. Wireless Application Protocol (WAP)
1. Ethernet
Ethernet is a technology/protocol that is used over Local Area Network (LAN). Ethernet is based on bus topology but can also be used in star topology. It uses cables to transmit data, most common in LAN networks, and is easy to install and maintain. Another version of Ethernet called Fast Ethernet is 10 times faster than original Ethernet. Gigabit Ethernet is even 10 times faster than Fast Ethernet.
2. Token Ring
Token Ring is based on ring topology although it can also be used in bus topology. A special signal called token is used to access any computer in the network. The token continues to circulate over the network. Any computer that needs to transmit data must first take the token and then it can start transmission. This avoids collision in which two computers simultaneously try to transmit data and therefore error occurs.
3. Transmission Control Protocol/Internet Protocol (TCP/IP)
In this protocol, data transmission is managed by dividing the data into different pieces called packets. Each packet of data contains a part of actual data, source computer’s address, destination computer’s address, and information for reassembling data at destination computer. These packets of data travel along the fastest available path in the network. This type of data transmission is called packet switching and is commonly used in Internet communications. This is the reason that the protocol is also called Internet Protocol (IP).
4. Wireless Application Protocol (WAP)
Wireless application protocol is used by mobile users to access the Internet and e-mail services. In WAP, client-server network architecture is used. Mobile device uses client software to connect to the sewer computer of Internet Service Provider (ISP). Mobile devices that support WAP are called WAP-enabled devices. The demand of WAP-enabled devices is increasing day by day.
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