 I am working as a student professor in computer science and engineering department at Valsh Institute of Technology, Solaapur. Today I am going to give the lecture on DNS in the internet. Now, let us see the learning outcomes of this lecture. At the end of this session, the students will be able to explain the concept of DNS in the internet. Second one is students will be able to explain the concept of resolution. These are the two topics I am going to cover in this lecture that are DNS in the internet resolution. Why we have to use DNS in the internet, ok. DNS is in the previous lecture we have already discussed about the DNS domain name system concept why we have to use in the internet, ok. If the user has told a huge amount of data in a single system to search the data based on the client request, the user may face the problem for that we have to use DNS concept in the internet also. Based on that only they have given three types of DNS in the internet that are generic domain, country domain, inverse domain. This one is a generic domain, country domain, inverse domain. Now, let us see one by one in detail. First one is generic domain. Generic domain defines all the registered host acts according to the generic behavior. It means there are so many domains are there here that is 0, bits, .com, .cope, .edu, .gov, .info. These are different domains are there. In this domain I have taken only one example that is .edu. This is a main domain that is edu these are the subdomains. These subdomains how register to this main domain. These subdomains how to act according to the generic behavior of this domain that is .edu that is .educational that is challenger and then atc.fsda.edu. These are subdomains how register to this main domain. These how to act according to this domain. That is what are the different full what are the full form of these different domains .euro that is airlines and aerospace companies like this. These are the different domains how to use for different purposes. Second one is country domain. It uses two characters country abbreviations for example US for United States. Second one is second label can be organizational or they can be more specific national designations ok. The United States for example use state abbreviations as a subdivision of US for example ca.us for here I have taken this is a good example for DNS in the internet a n g a dot c up dot c a dot us it means the ANZA. The ANZA college is there in California is there in California is there in US can be translated it means the ANZA college in California is in California is there in United States ok. This is country domain here we have to use two characters for defining the country domain ok. These are different subdomains are there here I have taken only one example that is ANZA dot c up dot ca dot us ok. Next one is universe domain. It is used to map an address to a name for example when a server have issued a client request from the client to do a task ok the server ask its resolver to send a query to the DNS server to map an address to a name to determine if the client is on the authorized list. If the client is there in authorized list then only the client can assign some IP address to the client request. If it is not there in the authorized client list the server can reject it and then it can refoward to the client only ok. These are the this is a good example I have taken here 121 dot 45 dot 34 dot 132 dot in underscore address then ARPA this is a one IP address. This IP address the client can send this IP address to the server the server can checks this IP address is authorized IP address or not. If it is authorized then only it can accept if it is not authorized then it can rejects the IP address ok then it can assign some IP address to ARPA is one of the historical places ok. Then inverse domain as the name itself indicates first the user can send the IP address then based on that only he can get the historical places ok. Next one is resolution this resolution means mapping a name to address or an address is to a name is called name address resolution. In this resolution there are so many sub topics are there that are first one is resolver, second one is mapping names to address, third one is mapping addresses to name, fourth one is recursive resolution, iterative resolution, last one is catching. Now let us see one by one in detail ok. First one is resolver DNS is designed as a client server application a host that need to map an address to a name or name to an address address calls DNS client called a resolver ok. The resolver access the closest DNS server with a mapping request. If the server have a has the information it satisfies the resolver it either refers the resolver to other servers or has to other servers to provide the information. For example after getting the client request the server can check the IP address is available in the server or not. If it is available in the server then it can send the reply to the client. If it is not available it would not reject it can refer to the some other users to send the information required to the client. That is resolver. Next one is mapping names to an address ok. Most of the time the resolver can give a domain name to the server and ask for the corresponding addresses in the mapping names to an addresses. In the reverse form mapping address to a address to names. A client can send the IP address to a resolver to be mapped to a domain name. To answer queries of this kind DNS uses the inverse domain. The good example for mapping address to a name is an inverse domain. In this the user can send the IP address and then he can request the information required to the client ok. Based on that only the user can get satisfied ok. Next one is think and write. This can contains one question list the difference between mapping names to addresses and mapping addresses to name ok. Pause the video now and answer the question. Now let us see the answer for this question. Mapping names to address. In this case the server checks the generic domain or the country domains to find the mapping. First the user can send the names based on that name only the client have to assign some IP address to the client request that is addresses. If the domain name is from the generic domain, generic domain session the resolver can receive a domain name such as chl that is challenger.atc.fsda.edu ok. If it is country domain that he can gets the the ANZA college is there in California California is in Coofer new Coofer new is then US that example he can get ok. Second one is mapping address to a name however in the request the IP address is resolved and two labels in address and ARPA are appended to create a domain accepted by the inverse domain session. For example if the resolver receives an IP address 132.34.45.121 the resolver first inverts the addresses and then adds the two label before sending I mean that two labels are the addresses to the this IP address. Next one is recursive resolution recursive means the user can get the answer itself it means the client or resolver can ask a ask for a recursive answer from the name server this means that the resolver accept the servers to supply the final answer it means this is a block diagram for recursive resolution here client is a here the server here first the client can send the request to server if the data is available in this server then he can reply if it is not available then again it can forward it to the next user again the this next user can search the required data from the client if it is available then he can reply otherwise it can send the same request to the next server the same procedure they will follow until to get the data to the client request ok after getting he can send the reply through the same path ok here 1 2 3 4 and 5 these are the request and then 6 7 8 9 10 are the responses whatever the data is required to this client this data is available in this system ok until to get the answer the query will be forwarded to the next only that is recursive resolution the process can cause itself until to get the required answer ok next one is attrative resolution the attrative resolution if the client does not ask for the recursive answer the mapping can be done attratively if the server is authoritative for the name it sends the answer for example here client is there there are some in servers are there here 1 2 1 communication will be happened until to get the required answer here client server can send the request and get the reply data is not available in this one again he can get the reply the same procedure they have to follow to the next users also edu then root server and this one here the data is available at the end here they can get the data same procedure we have to use in a recursive resolution here 1 2 1 communication is there the user can forward the same query until to get the data ok these are the references I have used for repairing the OPPT. Thank you.