 Hello everyone. Myself, Mr. Chopa, I am Madhika, I am working as an assistant professor in computer science and engineering department at Walton Institute of Technology, SolarPore. The last two videos we have discussed about computer network and then use the subcomputer network network hardware. Today we will be going to discuss about network software, learning outcome. At the end of this session, students will be able to describe the concept of protocol hierarchies and state the concept of design issues for the layers, agenda, protocol hierarchies, design issues for the layers, connection oriented versus connectionless services, service primitives and relationship of services to protocols. These are the points I am going to cover in this video about network software. Network software is now highly structured because while transmitting any data from one place to another place, the user should have to use any one of the software. The fundamental idea is that here nowadays the software can be used for store and forward purpose. It means before transmitting the data, the user should have to store the data, whatever the data they want to transfer from one place to another place. Then after storing the data, they have to forward. If the data is misused or somewhere it is dropped and discarded, then that time the user have to check out the original data in the stored places. Protocol hierarchies. First, let us see what is protocol? Protocol is a set of rules that can govern the data communication between each other. Hierarchies, it means transmitting the data from one place to another place by using sequences. First point is to reduce their design complexity and most networks are organized as a stack of layers one below it. It means the user can pass the data one layer to another layer, one layer to another layer and layer below the layer for hierarchy purpose. Interfaces. After transmitting the data from one layer to another layer, both the layers present layer and the next layer, they have to interface with each other. If the next layer is free, then only the current layer can pass the data. If the next layer is busy, then the current layer has to wait. That both the layers, each and every time they have to use this interface concept, it means they have to communicate with each other. Then if it is free, then only it is possible to pass the data. Next one is a list of protocols used by a certain system. One protocol per layer is called protocol stack. Protocol hierarchies. A set of layers and protocol is called a network architecture. The network architecture, we have to use a number of layers and number of protocols for different layers. That protocol can place a different rule for different layers while transmitting the data. This is a block diagram of layers, protocols and interfaces. Here the user one is there in the host one, then user two is there in host two. These two users want to send the data and receive the data, it means the current layer that is layer five, then how to interface with the next layer that is layer four and then if the next layer is free, then only the current layer they can pass the data. If it is busy, the current layer how to wait until the next layer will be get free. Then after if it is free, then only the current layer can pass the data. The same procedure, they how to follow from layer four to layer three also. Then layer three is free, then the current layer, I mean the layer four can pass the data to next layer. Then again the layer three can interface with the layer two. The layer two can interface with the layer one also. Then after interfacing, then they have to send the data to the receiver side through this physical medium. They can use any physical medium from sender to the receiver. In the receiver side also, they how to use the same concept, they how to interface with each other. If the next layer is busy, then how to wait if it is free, then only it can pass the data to the next layer. I mean in a parallely, both the layers are virtually communicate with each other while transmitting the data. This is a block diagram for layers and different protocols and interfaces each layers. This is how the user can pass the data. In the previous diagram, I just I said both the layers can interface and then they how to send the data, how they can send, how they can interface and what they how to add it means. In this diagram, they how given actual data transmission, okay. This is an example, information, flow supporting, virtual communication layers it means. Layer five want to transfer the data to the receiver side. How they how to pass the data and then how they how to add the current layer information to that particular data. It means here it is a this is M is in message. This message want to transfer to the receiver side. This message can pass the layer five to the layer four. Both the layers are interface which either after interfacing it can pass the data to the next layer. This M or the layer four can adds its own header information, H four indicates the header, four indicates the fourth layer. That is H four can adds the information related to the current layer. Next, if this message is divided into two part that is M one and M two, it can pass the data to the different users in the layer three. That means M one and M two, M one and then whatever the data is issued from the previous layer that is H four is in data related to the fourth layer. Then H three is in header about the layer three. Here also we have to add H three it means header about the layer three. Then message M two and then they can pass the data to the next layer that is M one is an original message. H four is an information about the fourth layer. H three is in layer information about the third layer. H two is in information related to the second layer. T two is in trial information they have to add before transmitting the data in the second layer. Then after preparing the how to send the data to the receiver side through this machine. This is source machine and destination machine. The data can pass it to the receiver side. The receiver side also they how to check out the whatever the process they how to follow it in the sender side. That means T two they can check it out the trial information about the second layer. T is in trial, two is in information about the second layer. M one is in information information, H four is in fourth layer information, S three third layer information, S two is in second layer header information. Then they can pass the data to the third layer, after processing then it can send it to the fourth layer. However the data is there in the sender side of the fourth layer. Same data is there in the receiver side also. Then original message will send it to the receiver side. Like this the user can send the data by using the protocol hierarchies. That means sequence wise they have to send the data to the receiver side. This is a dotted line indicates the actual line indicates the actual communication that is the dark line indicates this in actual communication and dotted line indicates the virtual communication between both sender and receiver. They can virtually communicate in a data communication or transmitting the data. In a communication they have to virtually communicate with each other. Design issues for the layers. Some of the key design issues are error detection. While transmitting the data if the data is discarded, data is corrupted where exactly the data is discarded we have to find out that is error detection. In the error correction after detecting the errors the user can find out the how to find out the errors and after finding the errors how to detect how to correct that errors they can use some different methods for correcting the errors that is CS and Hamming code they can use the different methods for error detection as well as error correction. Second design issues it is concerned the evaluation of the network growth is that different network technologies often have different limitations. Third design issues the resource allocation network provides services to host from their underlying resources. Okay congestion overloading of the network it means sender side is sender side process is slow the receiver side is high in that time the user can face a problem related to the congestion it means they can face a problem related to the spacing. Okay quality of services is the name given to mechanism that reconcile these competing demands. Reliable connection oriented services has two minor variations it is message sequence and byte streams. Message sequence they can send the messages in the sequence wise and byte streams they can send the data in the form of zero sign ones it means bytes in the form of bytes they can send the data. Unreliable connection less services is often called datagram services means here we have to use different protocol or one protocol that is UDP protocol that is datagram services while providing the datagram services. Next one is think and write it can contain one question that is list and explain different services of connection oriented versus connection less now pause the video and answer the above question. The answer for the above question is connection oriented services to talk some someone you pick the call phone pick up the phone dial the number and talk and then hang up. Connection less services is the model of turn the postal system okay when the intermediate nodes receive a message in full before sending it on to the next node this is a this is called store and forward switching. This is a simple explanation about the connection oriented as well as connection less. Connection oriented services reliable message streams reliable byte streams and unreliable connection it can goes to the global message region sequence of pages movie download and then vice-over-internet connection less unreliable datagram electronic junk mail acknowledgement datagram text messaging request reply database query service primitives primitives is a set of operations it means service is formally specified by a set of primitives or operations while transmitting the data from one station to another station the user should have to perform different operations that are connect a set of primitives available depends on the nature of the services being provided okay the primitives for connection oriented services are different from the from the from the connection less services okay there are total six primitives are there that are listen what is the meaning why we have to use a listen operation it means block waiting for an incoming connection connect this primitives can be used to establish a connection with a waiting peer accept accept an incoming connection from the peer ratio block waiting for an incoming messages send send a message to the peer disconnect terminate the connection these are the different primitives we have to use in a communication service primitives this is a client machine this is a server machine this can be used for sending the data and issuing the data by using some primitives okay these are the references high use for preparing the above video thank you