 Hello everyone. Myself, Mr. Chopa, I am Madhga, working as an assistant professor in computer science and engineering department at Walchin Institute of Technology, SolarPore. Now I welcome to the session on Network Layer Design Issues. Learning outcome. At the end of the session, students will be able to describe the different design issues of network layer. As we have discussed in the previous video, there are total 5 design issues are there. In this video, we will discuss about the next three points that is the implementation of connectionless services, implementation of connection oriented services and comparison of virtual circuit and datagram circuit. About network layer, we have already discussed in the previous lecture like it handles the service request from the transport layer and further forward the services request to the data link layer, ok, for more in the main role of the network layer is to move the packet from sending host to the receiving host, ok. Here, the two classes of services, the network layer can provide to its user, ok. Two main categories, two different organizations are possible depending on the type of services offered. For example, here two classes of the services like connection oriented classes, this one we have to use for forwarding the packet, two different organizations are possible depending on the type of the service offered. It means they may use a connection oriented services or connectionless services. It means that depends upon the organization, they may use a connection oriented or connectionless. Now, they have given the connectionless services offered packets are injected into the network individually. The network, if the user is using the connectionless services, first the user can put the packet or inject the packet in the network and without using any physical media between two transmitter, he can transfer the data to the next user, ok. That is the no advanced type is necessary because here we would not use any connection between both transmitter as well as receiver without using any connection directly he can put the or inject the packet in the network individually and then he can forward the data. So, for that no advanced set of is needed, it means directly we mentioned the data or datagram or datagrams and data networks we have to use for forwarding that, datagram is a set of information. Here if connection oriented services, we have to use some connection, ok. Here directly if there is no connection between both our transmitter and receiver directly, we have to send the data. Here there is no need to use a network set of, ok. Suppose that the process P1 is in below figure has a long message for P2, ok. There are two process are there P1 and P2. If these two process are users want to send the data and retrieve the data by using connectionless services. Then how it can handles? It can it hand hands the messages to transport layer with instruction to deliver it to process process P1 to P1 on host H2, ok. This is a simple example is there. Based on this we have to easily get the concept of a connectionless services here. Two process are there process P1 and process P2 here this is already we have discussed about this diagram that is ISPs that are internet service provider and some routers are there. And then how we have to send the data by using connectionless concept. Here they have given AS table initial and AS table later and then C is stable and E is stable. It means these are different routers are there. If the packet can reaches to this particular router what will happen, ok. Here the process P1 can forward the data host H1 can forward the data to router A. And then in this one there is no source and destination directly source A is to A is not possible here dash is there. And then the B to B is also if the packet moves to the next router B to B is also no that is B to B only and C to C here there is no source and destination. And then E to C if the packet can reach to the E then that time we have two alternate paths then we may send to C also, ok. And then F to C because here the some alternates are there F here you may send the data through D as well as C also, ok. The destination and line they have given this through this line we have to send the packet based on that only they have given about this one that is A to A is dash and B to B we have to and then C to C and D to B. And then what are the different alternate paths are there to send the data by using wireless concept. And C's table is there we have to start from C here C to C it means there is no destination. C is only how to send the data the C may send the data by using two path that is the C may directly send to the D, E or E also and then E to E is no and then F to E we have to send the data. Same thing we have to use for E also, ok. And then network layer has to break it into four packets packet 1, 2, 3 and 4 and send each of them in turn to router A using some point to point protocol. In this below this diagram there are four packets are there how we have to transfer that only is there, ok. A has that is router A has only two outgoing lines B to B to C. So, every incoming packet must send to one of these routers because A has two outgoing lines the A may send the data to B as well as C also even if the ultimate destination needs to some other router, ok. At A packet 1 and 2 and 3 also are stored briefly and then having arrived on the incoming link first all the packets how to store in a A router then he can send the data or packet to the next user that packet 1, 2 and 3 may forward after storing the data, ok. The packet 1 is then forwarded to E and then F and then to F when it gets to F it is sent within a frame over the LAN to H2 because F is there is not there in a ISP that is internet service provided. Whenever the data can passes to F, E then the data will F then it will goes to the out of the ISP or out of the router then it will reach to the destination side they have given LAN that is H2, ok. Connection oriented how we have to send that by using the same concept by using connection oriented concept. Here for connection oriented services we need a virtual circuit network, ok. And then idea behind virtual circuit is to avoid having to choose a new route for every packet send here their virtual circuit it means here that S3 one more is there that is host 1 is there, host 2 is there, host 3 is also there. Here is also we have to send the data by using the connection oriented concept it means here the user may use some path between transmitter and receiver. By using that the user can transmit the data and here the user can use a virtual circuit the same procedure whatever we have discussed in the connection less services by using the by using that concept you may send the data and receive the data here they have given the A stable, C stable and E stable also what is A1 that is H1 is there, S3 is there that is H1 this one and then H3 this one by using that they have given the values that is 1, 1 that is F1 and then output is C, data may goes to this one that is C and here also C stable they have given, E stable also they have given. That is in the previous slide by using connection less concept he has forwarded by using the same diagram we may send by using the connection oriented by here it means here the user can use the virtual circuit network, ok. That is routing within a virtual circuit network, ok. Here host 1 has a established connection 1 with host 2 this connection is remembered as the first entry in each of the routing table, ok. The first line of A stable says that if a packet bearing connection identifier 1 comes in from host H1 it is to be sent to router C and given connection identifier 1, ok. Let us consider what happens if S3 has want to also want to establish a connection in to H2, ok. It chooses connection identifier 1 and tells the network then even S3 also want to send the data it means first you want to establish a connection because you want to send the data it means the packet it means they have to get the you have to get the connection and then it is possible to transfer the data. Then after connection establishment he can transfer the data it is establish a virtual circuit, ok. Next thing kind write it can contains one question list some comparison of virtual circuit and datagram circuit. Now pass the video and answer the question, ok. Now we can go to the answer issues and then datagram network and virtual circuit. Circuit setup not necessary in the wire like datagram network and virtual circuit it is necessary. The addressing each packet contains the full source and destination address and in virtual circuit network each packet contains short VC network virtual circuit numbers. And then state information routers do not hold state information about connection each virtual circuit requires routers table space per connection routing each packet is routed independently a route route route chosen when VC is set up all packets following. Then effects of router failure none except for packet lost during the crash all which is that virtual circuits that pass through the failed routers are terminated. Quality of services difficult here in this one that is virtual circuit network easy if enough resources can be allocated in advance for each VC congestion control difficult here easy if enough resources can be allocated in advance for each virtual circuit, ok. Next one is service provided to the transport layer both virtual circuit and datagrams have their supports and the destructors, ok. Detectors a related issue is that the destination address used in datagram networks are longer than circuit numbers used in virtual circuit network because they have a global meaning send the data, ok. Yet another issue is the amount of table space required in a route memory, ok. In generally here if two users are sending the data and receiving it how they can manage by using connection oriented as well as connection less services, ok. These are the references I have used for preparing the above PPT. Thank you.