Were you searching to download Communication Protocols PDF Notes? Well, you are at right place. I have given the download link of the pdf below but before that must read this article Communication Protocol to know what topics are covered in that pdf.

Let us what is Data Communication, Data Communication means exchanging of data between the two nodes through some link which is a transmission medium for example cable.

Data flow means data is going to flow from one node to another node.

There are three different flows:

  1. Simple
  2. Half duplex
  3. Full duplex

Firstly, the Simplex:  This communication is always unidirectional transmit.

One node will transmit and the other node will receive.

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For example: Keyboards, monitors

Keyboard is connected to CPU , Keyboard is going to give data to CPU whereas CPU is not going to give any data to the keyboard. Likewise, traditional monitors, whatever the data is there in CPU’s, that is going to be given to the monitor and monitor is not going to give information to the CPU. So in both the cases, the communication is uni-directional.

Coming to the Half duplex, the communication is in both directions but not at the same time, if one device is sending, the other can only receive, and vice-versa. And this will not happen at the same time.

For example: Walkie-Talkies.

We can talk as well as we can listen but we cant talk and listen at the same time.

Now we shall what is Full duplex, Communication is in both directions simultaneously.

It means a Device can send and receive at the same time

Example: Telephone lines

We can talk as well as listen simultaneously by using telephone lines. So this is called full duplex.

We will now see what are protocols

All communication schemes will have the things that are in common below:

  1. Sender or a source
  2. Receiver or destination
  3. Media or channel

Rules or protocols will provide us all the methods of communication.

What if there are no protocols, if one person speaks with high speed which the person at the destination can’t handle, then it will be a useless communication. They have to mutually agree upon certain rules, so what if one person speaks in the language which other person can’t understand, so still there is no use in the communication, again the communication becomes useless. So to avoid these type of situations there is a need for protocol Protocols is a set of rules which will govern the communication of data.

The determination of protocol is:

What is to be communicated in the network ?

How it is to be communicated in the network?

When it is to be communicated in the network?


Now let’s know about protocols in the human communication.

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Protocols are necessary for human communication and includes:

  1. There should be a sender and receiver there can be single or group of senders and receivers.
  2. Human communication is effective only when there is Common language which has grammar to understand
  3. Speed and delivery timing of speech is also very important
  • Confirmation or acknowledgement requirements.

One person should get confirmation or acknowledgement from the receiver that he has got the data which the person has sent

Protocols- Network communication:

So when there is a sender and a receiver and then the communication will be effective when these protocols are addressed properly.

The message should be encoded and the message should be formatted and should have encapsulation, Message timing is also very important in network communications.

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The size of the message is also very important because the link can’t send big data, if there is a low capacity link.

At the same time, the delivery options should also be there, whether the message is for one destination or for group of destinations in the network all these information should be there in delivery options.

The elements of protocol are:

  1. Message encoding
  2. Message formatting and encapsulation
  3. Message timing
  4. Message size
  5. Message delivery options.
  1. Message encoding means the message source computer generates the message it gives the message to the encoder in order to generate signals once the data is converted into signals now it is given to transmitter for transmission, so we have two kinds of transmission here one is wire medium and another is wireless medium. The source has to understand to which medium it is connected to.

    If it is a wired medium the data has to be connected into signals in order to make the data transmission on the wired medium. If it is a wireless medium the sender has to encode the data in the form of waves. And once the data is sent through the transmission media the receiver will receive the data and decodes it decoding means understanding it after understanding it properly it means the message has reached the destination this is what message encoding means.
  2. Message formatting and encapsulation:

Both sender and receiver must agree on certain formats mutually which is knows as “Agreed format”. At the same time  when the receiver receives some the data, it should identify who has sent this data, we are going to add some information with the data in order to identify the sender and the receiver. We are going to encapsulate some things such as source information and destination information with the data. So that the right senders and receivers are identified.

  • Message sizing: If there is a very big message to be communicated to the destination, Humans will break long messages into smaller parts or sentences. Long messages should also be broken into smaller pieces to travel over a network , Computer should also break the data into smaller parts which this transmission medium can handle when the link capacity is less and the data is big, this is what message sizing is.

  • Message timing: It deals with Flow control and Response timeout, Let us assume the sender is very fast and the receiver is very slow, the sender can send data in very high speed, and receiver cant handle that speed, if there is no flow control mechanism, he can keep on sending data continuously but receiver can receive the data.

    So the entire communication will become useless, it is the responsibility of the protocol to provide flow control mechanism at the same time the receiver has to acknowledge the data when the sender has sent the data.

    If the acknowledgement is not sent to the sender by the receiver, then sender has to wait for sometime after the time expires the sender will again send the data to receiver, so that we can ensure the guarantee delivery. And it is the responsibility of the protocol to tell how much time the sender has to wait for acknowledgement.
  • Message delivery Options: There are three delivery options.
  • Unicast
  • Multicast
  • Broadcast

Unicasting means one sender and one receiver, it means sender is going to send data to exactly one receiver in the network, if the sender is sending data to exactly one destination it is called as uni-casting.

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Multicasting means sender sends the data to set of receivers but not to all then it is multicasting.

Broadcasting means the sender sends the data to all the participants in the network then we call as Broadcasting.

We will understand protocols and its role in computer networks. The protocols include: File Transfer Protocol, TCP/IP,User Datagram Protocol, Hypertext Transfer protocol, Post Office Protocol, Internet Message Access Protocol, Simple Mail Transfer Protocol.

These protocols are created by W3C(World Wide Web Consortium) and IETF(Internet Engineering Task Force). DDOS(Distributed Denial Of Service attacks is being against by Authentication protocols. All these protocols will help to work against different kinds of abuse operations. Other communication protocols will be used for data packets in global network areas. All these protocols depend on the technologies , so as the technology evolves these protocols also evolve in generations to generations. That is why internet protocols are very popular.

Another elements of protocols are:

  1. Syntax
  2. Semantics

Syntax is nothing but structure or format of the data, it also indicates how to read the bits.

Semantics is helpful in interpreting the meaning of the bits and also explains which field defines what action.

Standards: Standards provides guidelines to manufactures or vendors or the government agencies and other service providers to make sure that the interconnectivity which is important in current market place and also in international communication, like a particular organization will follow standards to develop any product that is useful in market.

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Also Read:


It is agreed upon rules.

Different standards are there:

1.De facto

2.De jure

De facto means by convention or by fact.

De jure is by law or by government.

ISO(International Standard Organisation) having international telecommunication union(ITU) and its having IEEE and also has ANSI standards.

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