Transmission Media

What is transmission media ?

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1. A transmission medium is a route that transmits information from a source to a receiver.
2. Transmission media is a pathway that carries the information from sender to receiver.
3. We use different types of cable or waves to transmit data.

1. Transmission media are located below the physical layer.
2. Computers use signals to represent data.
3. Signals are transmitted in form of electromagnetic energy.

Classification of Transmission Media:-

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What is latency?

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1. Latency is the time it takes for data to pass from one point on a network to another. 

Example:- Suppose Server A in New Delhi sends a data packet to Server B in Banglor. Server A sends the packet at 04:38:00.000 GMT and Server B receives it at 04:38:00.145 GMT. The amount of latency on this path is the difference between these two times: 0.145 seconds or 145 milliseconds.

Most often, latency is measured between a user's device (the "client" device) and a data center. This measurement helps developers understand how quickly a webpage or application will load for users.

Latency is the amount of time a message takes to travel a system. In a computer network, it is an expression of how much time to it take for a packet of data to get from one designated point to another. It is sometimes measured as the time required for a packet to be returned to its sender.

What is Network Bandwidth?

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1. Bandwidth is the maximum amount of data that can be transmitted through a link, from a source to a destination. Bandwidth is not a real-time measurement, it refers to the overall capacity of a network link. When you monitor bandwidth usage it is typically measured by megabits per second (Mbps) or gigabits per second (Gbps).

In the picture above, the blue link between PC1 and PC2 has a network bandwidth of 400 megabits per second (Mbps). This simply means it has the overall capacity to transmit data at 400 Mbps. This doesn’t mean data will always transmit that much data at once, it just means it can.

Let’s look at an example of a highway to better illustrate bandwidth.

Above the highway can handle 10 care per second, this represents its bandwidth (max capacity). This doesn’t mean the road will always have 10 cars per second going across it, it just means the road has the ability to handle 10 cars per second.

What is Network Throughput?

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1. Throughput is the measurement of actual data that is transmitted between two networked devices. Throughput can also be referred to as data transfer rate and is measured in bits per second (bps).

"Above the blue line is the max bandwidth of the connection, and the red line is the throughput (how much data is going through the connection in real-time). So the blue connection can handle 400 megabits per second but only 1000 kilobits per second is being used by the two computers."

Bandwidth vs Throughput

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Bandwidth = Maximum amount of data that can be transmitted.

Throughput = Actual amount of data being transmitted between two devices.

This network has a 10 Gbps connection from the PC all the way to the internet. When the PC downloads a file from the internet it only has a throughput of 100000 kbps (100 Mbps). The PC is only using 1 percent of the bandwidth.

What can affect Network Throughput?

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I have a 1 gig connection but my download speed is slow.

This is very common, throughput is often lower than bandwidth. This can be frustrating but again it’s very common. Below are the top reasons your throughput is lower than bandwidth.

• Other Users and Devices Consuming Bandwidth

• Network Equipment that causes a Bandwidth Bottleneck

What is Attenuation ?

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1. It means loss of energy. The strength of signal decreases with increasing distance which causes loss of energy in overcoming resistance of medium. This is also known as attenuated signal. Amplifiers are used to amplify the attenuated signal which gives the original signal back and compensate for this loss.

• Distortion – It means changes in the form or shape of the signal

Noise – The random or unwanted signal that mixes up with the original signal is called noise. There are several types of noise such as induced noise, crosstalk noise, thermal noise and impulse noise which may corrupt the signal.

 

1. Induced noise comes from sources such as motors. These devices act as sending antenna and transmission medium act as receiving antenna. 
2. Thermal noise is movement of electrons in wire which creates an extra signal. 
3. Crosstalk noise is when one wire affects the other wire.
4. Impulse noise is a signal with high energy that comes from lightning or power lines