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Computer Communication & Networks

Explore Domain Name System (DNS) in application layer focusing on name spaces, hierarchy of name servers, and name-address resolution. Learn about domain names, labels, distribution, and DNS in the internet.

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Computer Communication & Networks

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  1. Computer Communication & Networks Lecture 26 Application Layer: Domain Name System http://web.uettaxila.edu.pk/CMS/coeCCNbsSp09/index.asp Waleed Ejaz waleed.ejaz@uettaxila.edu.pk

  2. Application Layer

  3. Application Layer Topics to Cover DNS Remote Logging Electronic Mail File Transfer

  4. Name Space • To be unambiguous, the names assigned to machines must be carefully selected from a name space with complete control over the binding between the names and IP addresses.

  5. Domain Name Space • To have a hierarchical name space, a domain name space was designed. In this design the names are defined in an inverted-tree structure with the root at the top. The tree can have only 128 levels: level 0 (root) to level 127.

  6. Domain name space

  7. Domain names and labels

  8. Domains

  9. Distribution of Name Space • The information contained in the domain name space must be stored. However, it is very inefficient and also unreliable to have just one computer store such a huge amount of information. In this section, we discuss the distribution of the domain name space.

  10. Hierarchy of Name Servers

  11. DNS in the Internet • DNS is a protocol that can be used in different platforms. In the Internet, the domain name space (tree) is divided into three different sections: generic domains, country domains, and the inverse domain.

  12. DNS IN THE INTERNET

  13. Generic Domains

  14. Generic domain labels

  15. Country domains

  16. Resolution • Mapping a name to an address or an address to a name is called name-address resolution.

  17. Recursive resolution

  18. Iterative Resolution

  19. once (any) name server learns mapping, it caches mapping cache entries timeout (disappear) after some time DNS: caching and updating records

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