 working as a student professor in computer science and engineering department at Walton Institute of Technology, Sholapur . I welcome to the session on Network Layer Design Issues ok, Learning Outcome. At the end of this session students will be able to describe the different design issues of network layer ok. As in the store in forward packet switching services provided to the transport layer, implementation of connection less services, implementation of connection oriented services and comparison of virtual circuit and datagram circuit. In this video we will discuss only first two topics that are store in forward packet switching and service provided to the transport layer. Remaining design issues like implementation of connection less services and connection oriented services and comparison we will discuss in the next part that is part 2 of the design issues. Now, let us see one by one store in forward packet switching. Before going to that direct network layer design issues, what about network layer? Network layer is the one of the OS reference model or it is a fourth layer of OS reference model. In this we use a user can send the data in the form of packet from one station to the another station. Sending the data or sending the data whatever different issues or problems the user may face ok. It handles the service request from the transport layer and further forwards the service request to the data link layer. It means it can get the data from the different layers and it can send the data request to the next layer that is data link layer ok. The main role of the network layer is to move the packets from sending host to the receiving host or sending station to the receiving station ok. Next the key design issue is determining how how packets are routed from source to the destination. It means in this main key design issue is how we have to determine how the packets are routed from source to source stations to the destination station ok. It is unlike DLL that is the data link layer which has the more modest goal of just moving packets from one end of the wire to the other end. It means until DLL how we how to send the data from one station to another station and then while sending that how the user can face the problem or what are different problems the user may face that is there in this one just you can see that that is network layer is the lowest layer that deals with the end to end transmission. Here we have to send the data from node to node as well as end to end. In the network layer the user can send the data end to end ok by using the concept of end to end we have to send the data. Next that is first design issues that is the store and forward packet switching ok. Packet is stored there until it has fully arrived and the link has finished its processing by verifying the checksum. You know what is checksum? Checksum is a error detection method while sending the data from one station to the another station. Here the user can the user won't forward the data until he received all the data from the sender side. After receiving all the data first he can store the data in one station that is sender station. After receiving all the data then he can go to the next step that is forwarding the packet to the next station then it is forwarded to the next router along the path until it reaches the destination host. Where it is delivered this mechanism we can call it is a store and forward packet switching. It means if the user want to transfer just you can take a simple example two stations are there one is a transmitter and another one is a receiver transmitter having 10 packets want to transfer to the next user. He can send the data or packet until all 10 packets how to send to the one machine that after receiving all the 10 machine to that particular devices he can store the data in one machine after receiving all 10 packets then he can go to the next step that is forwarding the packet to the next user that is store and forward it means first he can receive all the data how many data they want to transfer after receiving then he can forward the data to the next data packet to the next user that concept we can call it is a store and forward packet switching. The major component of the networks are ISPs equipment ISPs equipment that is internet service provider mechanism that internet service provider equipment shown inside the shaded O line outside the customers equipment. Now next one more diagram is there in this one that is customer equipment is there that outside the O well how we have to. In this diagram just you can see this is a simple example how we have to use the concept of store and forward packet switching. Here process one is there and then process two is there here the different routers are there ISPs are there here process one he can he want to transfer the data to the process two it means he can send the data to different routers here five routers are there or six routers are there out of six five routers are there ISP and one more is a out of router okay here router A, B, C, D, E like these are total five routers are there the host A or process B when want to transfer the data to host B then he can prepare the packet and then he can forward that packet to the network ISP that is internet service provider and then this internet service provider he can check it can contain different routers routers can take the packet from a host and it can change the IP addresses physical the logical addresses and he can forward the different packets to differ by using different paths okay after receiving all the packet he can forward that packet to the next user that is processor p2 it means here just here just simple example they have taken actually this host one want to transfer 10 packets it means all the packets well first it will goes to the A then A may have a different routes that is the two paths are there the A may transfer the data through this router B router or C router the packet may transfer through B router or C router at the end the data will goes to E and then the E router can pass the data to the next user here F one more router is there that is not there in a ISPs or internet service provider range okay by using this concept the user can send the packet this is an environment of the network layer protocol here host one is directly connected to one of the ISP that is A routers then A perhaps as a home computer that is plugged into a DSL domain okay or modem DSL modem they can transfer the data okay in contrast H2 is on a LAN which might be an office internet with a router F wound iron operated by the customer it means here host one is there in different places and host two is there in different places it is there in the LAN the ethernet they have connected then by using this store and forward it means first they can store all the data in this one and then he can forward the data to the next user okay the network layer provides the services to the transport layer at the end of at the transport layer or transport layer interfaces different services are there that is service should be independent of the router technology the transport layer should be sealed it from the number type topology of the routers present okay network address made available to the transport layer should use uniform numbering plan even across LAN and VAN okay the designer of the network layer have a lot of freedom in writing detailed specification of the services to be offered to the transport layer with these are the different services are there the this part can contains one question that is what are the different network layer service primitives now pause the video and answer the above question okay now we can go to the question answer for the this question there are two services are there that our first one is the sending packet and second one is the receiving packet in the sending packet the user can prepare the packet and then user can put all the information whatever the information is necessary to send the packet and then after putting the information in the send packet then he can go to the next step that is forwarding the packet to the next user in the receiver side also the receiver can check the all the information is necessary whether the data is issued from the proper user or not they can they can check out the information like these two services the that is the question is the that is network layer service primitive these two primitives we have to use are these two operations primitive means operations we have to use in store and forward places or store and forward issues okay next one is services provided to the transport layer continue just is in a in particular no packet ordering and flow control should be done because the host are going to do that anyway and there is usually title to be gained by doing it twice means how the user can send the packet and receive the packet by using by using different operations okay this reason is an example of the end to end argument okay design principle that has been very influent in shaping the internet okay this is an example just they have given the simple example how we have to send the data and to show the data whether it is an end to end or no to no end to end argument the design principles that has been very influent in shaping the internet okay the each packet must carry the full destination addresses because each packet sent is carried independently of its predecessor it means independently it means while sending the data two or more than two devices are there that whatever the data we are receiving from the different paths that all the packets are user is sending five packets at a time it means all the packets should be independent to one another okay the other camp argues that the network should provide a reliable connection oriented services while transmitting the data to the next user here they claim that 100 years of successful experience with the worldwide telephone system is an excellent guide as an example this one the quality of services is the dominant factors and without connecting in the network quality of services is very difficult to achieve especially a especially for real time profit such as voice and video even after several decades this contours is still very much live okay here by using this concept the user can send the data and issue the data by using network layer concept okay the remaining part of this one we will go to the next topic that is the network layer design issues part two okay these are the references I have used to prepare the