Table of Contents
Transmission of Data:-
When data is transported between two or more computer systems in the form of binary code (bits), it is termed as data transmission. This movement takes place over cables, Wi-Fi or any other wireless medium in a network.
In the process of communicating digitally, data is transmitted electronically from one location to another by using standard methods. Let’s learn about the types of data transmission that happens over a network.
Type of Data Transmission:-
Data Transmission in a network is mainly of two types:
- Synchronous
- Asynchronous
Synchronous versus Asynchronous Data Transmission:-
| Asynchronous Data Transmission | Synchronous Data Transmission |
| Use of start and stop bits | No use of start and stop bits |
| Start and stop bits are of opposite polarity | No polarity of bits |
| No use of clock signal for synchronisation | Uses clock signal for synchronisation |
| Relatively slower data transfer rate because of start and stop bits. Relatively faster now as it is available with high rate links like 100G/40G/1G | Faster data transfer rate because of no start and stop bits circuits like OC-3/OC-12/STM-1/STM4 |
| The error rate is low | The error rate is high |
| Example -Ethernet | Example-SDH/SONET |
Let us now learn about the hardware or medium using which data transmission happens over the internet.
Medium of Data Transmission:-
Data (in the form of electromagnetic signals) is transmitted using specially designed network cables; either made of copper or fiber. Bandwidth, delay, installation, and maintenance costs are some of the characteristics of any transmission medium.
There are two types of transmission medium:-
- Wired Medium (guided)
- Wireless Medium (unguided)
Wired Medium:-
Wired medium has a defined physical path for transmitting signals because it is made up of physical cables. Therefore, it is also known as a guided medium.
The wired medium uses three types of cables namely:-
Twisted Pair Cables:
These are copper-based cable used for data transmission. The twisted pair is categorized Shielded Twisted Pair (STP) and Unshielded Twisted Pair(UTP).
The UTP can fall under different categories as shown in image. You will hear these terms while configuring a wired network.
Co-axial Cables:
These cables are also copper-based cables used for data transmission.
Fiber-optic Cables:
Optic cables carry light waves in comparison to copper cables that carry electronic waves for data transmission. Fiber cables have a high bandwidth capacity and high speed. They are noise-resistant and have low maintenance costs as compared to copper cables.
These cables work on the phenomenon of total internal reflection and consist of three parts namely, Core, Cladding and Coating and perform the following functions:
- CORE is the carrier of light signals
- CLADDING acts as a medium that carries light to the core
- COATING gives protection to cladding
Wireless:-
Wireless medium is unguided and uses an antenna for data transmission. It uses radio waves, microwaves and infrared waves to transmit data. However, a wireless medium is highly affected by adverse weather conditions.
Now, let us learn about the popular technique of network switching that is used for data transmission between networks.
Network Switching:-
Switching is a technique in networking that helps the transmission of data between different computer networks. Interconnected switches form a switched network that enables temporary connectivity between linked nodes. Data is moved from nodes to nodes until it reaches its destination node.
There are two methods of network switching, namely, Circuit Switching and Packet Switching. Let us learn about each one in detail.
1.Circuit Switching:
When data movement is in a continuous stream from source nodes to the destination node, it is termed as circuit switching. Circuit switching gives a fixed data rate.
Circuits switching consists of three phases to learn about each one in detail.
Connection Set-up Phase:
Firstly, a dedicated channel is established prior to the actual data transmission from source node to the destination node. Source and destination addresses are required for the connection set up between the source and destination node.
Data Transfer Phase:
Once the dedicated channel is established between the source and a destination node, the actual data transfer takes place in a continuous stream between the sender and the receiver.
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Disconnection Phase:
The connection is terminated or disconnected after the data transfer Phase and the dedicated resources get released.
Let’s look at the advantages and drawbacks of circuit switching.
Advantages of Circuit switching:
- Dedicated channel for data transmission between sender and destination node
- No delay or waiting time
- suitable for long-duration transmission because of dedicated continuous stream
Drawbacks of circuit switching:
- Technique because of a channel is being dedicated to data communication for a fixed duration of time. In cases, where there is no data transmission for a specified interval of time, the channel is wasted.
- It requires more bandwidth as it is a dedicated channel.
- Time-consuming as more time is required for the establishment of a channel between sender and receiver nodes.
2.Packet Switching:-
Packet switching was designed with the intention of sending a message in parts over any available link in the network. Data is transmitted from sender to receiver in the form of fixed-size blocks called “packets” via the transmission medium. Hence, packet switching gives a variable data rate. The message is then reassembled at the destination as per their sequense number. The internet and mobile phone technology like GPRS uses this technique.
A packet has two parts namely, header and payload
Header:
Header defines the beginning of a data block and directs the packet to the destination node.
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Payload:
Payload is the actual data that is to be transmitted between the sender and receiver. It is usually encapsulated in a frame.
Classification of the packet switching:-
Packet Switching is classified into two types:
Connection-less packet switching:
When data transmission occurs over any link that is free, it is known as connectionless packet switching; as there is no defined path established between the sender and the receiver. This type of packet switching is not reliable. packets are transmitted from source to destination via intermediate nodes using the asynchronous mode of transfer.
Connection-oriented packet switching:
In this technique, data transmission takes a single route to reach their destination. The data packets do not travel via different available paths. This saves transmission time and increases the data rate.
Advantages of packet-switched network:
- Efficient network
- Robust in comparison to circuit switching
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Drawbacks of packet-switched network:
- Do you know the transmission is delayed compared to circuit switching
- Files can get corrupted during transmission
- Entire file would not reach the destination as it is being sent in packets
- Files may reach in the wrong order and may require reassembling
- Requires huge RAM in case of a large amount of data transmission
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