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DNS Domain Name Server

DNS Domain Name Server. Group: 4. Group Members Names. Bilal Virk Sehrish Javed Maryam Azhar Rehan Ali. DNS. introduction. DNS (Domain Name Server). Brief Presentation. We could spend all Day. Unsure about level of technical expertise. Stop me at any point if you have a query.

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DNS Domain Name Server

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  1. DNSDomain Name Server Group: 4

  2. Group Members Names • Bilal Virk • Sehrish Javed • Maryam Azhar • Rehan Ali

  3. DNS introduction

  4. DNS (Domain Name Server) • Brief Presentation. • We could spend all Day. • Unsure about level of technical expertise. • Stop me at any point if you have a query.

  5. What This Talk Is About! • What Is DNS? • Why DNS Is Needed? • History of DNS. • Hierarchy of DNS. • How Dose It Works? • What Are Zones?

  6. What is DNS? • Computers use IP addresses for Internet Traffic. • IP Addresses Are hard To remember • So, We use Names Instead.

  7. What is DNS? (Cont…) • The domain name system is usually used to translate a host name into an IP address . • Domain names comprise a hierarchy so that names are unique, yet easy to remember. So , We Can Say DNS is used for name to IP resolution & IP to name resolution.

  8. History of DNS Host File System

  9. Old Solution (host.txt) • Back in the early 80’s when the internet was called ARPANET, consisted of few hundred computers, servers on MIT university Campus. • Held A file that listed the names and IP address of those few computers. • That File was Named As HOST.TXT. • When a new host was attached to ARPANET it needed the NAMES and IPs of others computers over ARPANET for that reason it would just contact MIT server and download the latest Host file.

  10. 128.4.13.9 SPARKY 4.98.133.7 UCB-MAILHOST 200.10.194.33 FTPHOST Old Solution (host.txt) • A centrally-maintained file, distributed to all hosts on the Internet • This feature still exists • /etc/hosts [Linux] • c:\windows\system32\drivers\etc\hosts [Windows]

  11. Hosts.txt Doesn't Scale • Huge file • Needs frequent copying to ALL hosts • Consistency • Always out-of-date • Name uniqueness • Single point of administration

  12. Hierarchy of DNS Domain Levels

  13. Hierarchy of DNS We Offten Forget This Little Thing which has a huge role in DNS Root Domain TOP level Domain 2nd Level Domain Host ,PC www .Yahoo .Com . www.Yahoo.Com.

  14. Hierarchy of DNS . (root) uk com net org co.uk Yahoo.com Iso.net isoc.org nsrc.org www.Yahoo.com ftp.Iso.net www.isoc.org tiscali.co.uk

  15. Hierarchy of DNS . (root) uk com net org co.uk Yahoo.com Iso.net isoc.org nsrc.org www.Yahoo.com ftp.Iso.net www.isoc.org tiscali.co.uk

  16. www.yahoo.com rootserver referral to ‘.com' DNS Servers www.yahoo.com .com server referral to ‘yahoo.com’ DNS Server www.yahoo.com ww.yahoo.com server Answer: 212.74.101.10 Example : www.yahoo.com

  17. Point To Ponder Root Address

  18. Root Address • In the Previous Slide We saw • Root Provided the Address for Com • Com Provided the Address for Yahoo • Yahoo Provided the Address for www.yahoo.com But What or Who Provided The Address For .Root Server?

  19. Answer • There is a Term called “ROOT HINTS” Root Hint: On the DNS server there is a file which contains the ROOT SERVER ADDRESS which Holds the address for the root servers. Thus, It Comes For the Root Server Address File Amazing Fact: There Are Only 13 Root Servers on the Whole Planet.

  20. Application e.g. web browser Authoritative DNS Caching ISP / DNS Resolver Non-Authoritative DNS. Request For IP Address IP Address Found

  21. Application e.g. web browser Authoritative DNS Caching ISP / DNS Resolver Authoritative DNS. Request For IP Address IP Address Not Found IP Address Found

  22. What is a resource record? • A domain contains resource records • Resource records are analogous to files • Classified into types • Some of the important types are, A,CNAME and MX

  23. The “A” Record • The “Address” record • One or more normally defines a host • Contains an IPv4 Address (the address computers use to uniquely identify each other on the internet) • Eg. The record: • www A 203.18.56.31 • In the yahoo.com domain, defines the host uniquely identifiable as “www.yahoo.com.” to be reachable at the IPv4 Address 203.18.56.31

  24. The “CNAME” Record • A CNAME defines an alias • Assign multiple names against single IP Adress • Eg. The record: • search CNAME www.yahoo.com. • In the yahoo.com domain, defines the name uniquely identifiable as “search.yahoo.com” to be and alias to “www.yahoo.com”

  25. The “MX” Record • An MX record defines the mail servers for a particular domain • Mail eXchange records hold the name of hosts, and their priorities, able to deliver mail for the domain. • Eg. The record: • ausregistry.com.au MX 10 mail • In the ausregistry.com.au domain, defines the host mail to be the priority 10 mail server for the “ausregistry.com.au” domain

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