Question

(a). suppose you are going to transmit a packet over osi network model. explain the working of router, gateway and switch. which device will be used if you face an issue of weak signals during transmission? also, mention on which level of osi model these devices will work efficiently. (b). attenuation, distortion and noise are the causes of transmission impairment. what would be the solution or how these causes can be improved.

Answer 1

Step 1:

OSI stands for Open Systems Interconnection.

OSI model was developed by the International Organization for Standardization(ISO). It is a reference model for how applications communicate over a network. The OSI model characterizes computing functions into a universal set of rules and requirements in order to support interoperability between different products and software.

The OSI model can be considered as a universal language for computer networking. It is based on the concept of divide and conquers, it splits up the communication system into 7 abstract layers, and the layer is stacked upon the previous layer.

Layers of OSI Model:

OSI model has seven layers which are as follows:

1. The Physical Layer
2. The Data Link Layer
3. The Network Layer
4. The Transport Layer
5. The Session Layer
6. The Presentation Layer
7. The Application Layer

Step 2

Routers – A router is a device like a switch that routes data packets based on their IP addresses. Router is mainly a Network Layer device. Routers normally connect LANs and WANs together and have a dynamically updating routing table based on which they make decisions on routing the data packets. Router divide broadcast domains of hosts connected through it.

Gateway – A gateway, as the name suggests, is a passage to connect two networks together that may work upon different networking models. They basically work as the messenger agents that take data from one system, interpret it, and transfer it to another system. Gateways are also called protocol converters and can operate at any network layer. Gateways are generally more complex than switch or router.

Switch – A switch is a multiport bridge with a buffer and a design that can boost its efficiency(a large number of ports imply less traffic) and performance. A switch is a data link layer device. The switch can perform error checking before forwarding data, that makes it very efficient as it does not forward packets that have errors and forward good packets selectively to correct port only. In other words, switch divides collision domain of hosts, but broadcast domain remains same.

Which device will be used if you face an issue of weak signals during transmission.

Router device will be useful mostly for issue of weak signals during transmissin.

Mention on which level of OSI model these devices will work efficiently.

All these three devices router, gateway and switch work efficiently at hardware layers such as physical layer, datalink layer and network layer.

Step 3

Transmission impairment:

In the data communication system, analog and digital signals go through the transmission medium. Transmission media are not ideal. There are some imperfections in transmission mediums. So, the signals sent through the transmission medium are also not perfect. This imperfection cause signal impairment.

It means that signals that are transmitted at the beginning of the medium are not the same as the signals that are received at the end of the medium that is what is sent is not what is received. These impairments tend to deteriorate the quality of analog and digital signals.

There are three main causes of impairment are,

Attenuation

Distortion

Noise

1.Attenuation:

Here attenuation Means loss of energy that is the weaker signal. Whenever a signal transmitted through a medium it loses its energy, so that it can overcome by the resistance of the medium.

That is why a wire carrying electrical signals gets warm, if not hot, after a while. Some of the electrical energy is converted to heat in the signal.

Amplifiers are used to amplify the signals to compensate for this loss.

2.Distortion:

If a signal changes its form or shape, it is referred to as distortion. Signals made up of different frequencies are composite signals. Distortion occurs in these composite signals.

Each component of frequency has its propagation speed traveling through a medium and therefore, different components have different delay in arriving at the final destination.

It means that signals have different phases at the receiver than they did at the source.

3. Noise:

Noise is another problem. There are some random or unwanted signals mix up with the original signal is called noise. Noises can corrupt the signals in many ways along with the distortion introduced by the transmission media.

Noise may be divided into four categories:

1. Thermal noise
2. Intermediation noise
3. Crosstalk
4. Impulse noise