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DNS 101: What it is, how it works
What is it? DNS = Domain Name System <ul><li>One large distributed database:  The  DNS </li></ul><ul><li>Client/Server sys...
A Brief History of DNS and BIND <ul><li>Late 60’s: US DoD Advanced Research Projects Agency creates ARPAnet </li></ul><ul>...
The DNS Tree Structure The Distributed Database
Who Manages What? Delegation of Authority
How does it work? Anatomy of a DNS Lookup <ul><li>Your PC Asks: </li></ul><ul><li>Q: Where is www.cira.ca? </li></ul>
How does it work? Anatomy of a DNS Lookup <ul><li>Office-mail asks: </li></ul><ul><li>Q: Where is www.cira.ca? </li></ul><...
How does it work? Anatomy of a DNS Lookup <ul><li>Office-mail asks: </li></ul><ul><li>Q: Where is www.cira.ca? </li></ul><...
How does it work? Anatomy of a DNS Lookup <ul><li>Office-mail asks: </li></ul><ul><li>Q: Where is www.cira.ca? </li></ul><...
How does it work? Anatomy of a DNS Lookup <ul><li>Office-mail asks: </li></ul><ul><li>Q: Where is www.cira.ca? </li></ul><...
How does it work? Anatomy of a DNS Lookup <ul><li>A: www.cira.ca is at 192.228.23.21 </li></ul>
How does it work? Anatomy of a DNS Lookup <ul><li>Your PC Asks: </li></ul><ul><li>Q: Where is www.microsoft.ca? </li></ul>
How does it work? Anatomy of a DNS Lookup <ul><li>Office-mail asks: </li></ul><ul><li>Q: Where is www.microsoft.ca? </li><...
How does it work? Anatomy of a DNS Lookup <ul><li>Office-mail asks: </li></ul><ul><li>Q: Where is www.microsoft.ca? </li><...
How does it work? Anatomy of a DNS Lookup <ul><li>Office-mail asks: </li></ul><ul><li>Q: Where is ns4.msft.net? </li></ul>...
How does it work? Anatomy of a DNS Lookup <ul><li>Office-mail asks: </li></ul><ul><li>Q: Where is ns4.msft.net? </li></ul>...
How does it work? Anatomy of a DNS Lookup <ul><li>Office-mail asks: </li></ul><ul><li>Q: Where is www.microsoft.ca? </li><...
How does it work? Anatomy of a DNS Lookup <ul><li>A: www.microsoft.ca is an alias for microsoft.ca.  microsoft.ca has two ...
How does it work? Anatomy of a DNS Lookup <ul><li>www.smallbusiness.ca hosted by hostingco.ca </li></ul><ul><li>hostingco....
How does it work? Anatomy of a DNS Lookup <ul><li>Q: Where is www.smallbusiness.ca? </li></ul><ul><li>A: I don’t know, but...
How does it work? Anatomy of a DNS Lookup <ul><li>Q: Where is ns3.hostingco.ca? </li></ul><ul><li>A: I don’t know, but I c...
How does it work? Anatomy of a DNS Lookup <ul><li>Q: Where is ns3.hostingco.ca? </li></ul><ul><li>A: ns3.hostingco.ca is a...
How does it work? Anatomy of a DNS Lookup <ul><li>Q: Where is www.smallbusiness.ca? </li></ul><ul><li>A: It’s at 192.0.2.8...
What if Something Breaks? Data Replication and Authority
What if Something Breaks? Dot-ca Data Replication
What Can The Data Say? Record Types <ul><li>Address Records (A) -- www.cira.ca is at 192.228.23.21 </li></ul><ul><li>Point...
What Does it Look Like? Sample .ca Zone Data <ul><li>microsoft.ca.  IN NS  ns1.msft.net. </li></ul><ul><li>IN NS  ns2.msft...
 
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DNS 101 - What it is and how it works

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DNS 101 - What it is and how it works provides a great explanation of what DNS, or Domain Name System is and how it works.

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Transcript of "DNS 101 - What it is and how it works"

  1. 1. DNS 101: What it is, how it works
  2. 2. What is it? DNS = Domain Name System <ul><li>One large distributed database: The DNS </li></ul><ul><li>Client/Server system with: </li></ul><ul><ul><li>Name Servers - contain information about some segments of the database </li></ul></ul><ul><ul><li>Resolvers - create queries and send them across the network to a name server </li></ul></ul>
  3. 3. A Brief History of DNS and BIND <ul><li>Late 60’s: US DoD Advanced Research Projects Agency creates ARPAnet </li></ul><ul><li>Updates sent to SRI-NIC; HOSTS.TXT published twice a week. </li></ul><ul><li>Early 80’s: TCP/IP added to BSD, and ARPAnet growth explodes </li></ul><ul><li>1984, Paul Mockapetris releases RFCs 882 and 883 (later superseded by 1034 and 1035); JEEVES released </li></ul><ul><li>1985, Berkeley releases first version of BIND, written by Kevin Dunlap </li></ul><ul><li>1993, BIND 4.9 is released by DEC, managed by Paul Vixie, assisted by others; 1994, BIND 4.9.2 is released by Vixie Enterprises; 1995, BIND 4.9.3 released by ISC </li></ul>
  4. 4. The DNS Tree Structure The Distributed Database
  5. 5. Who Manages What? Delegation of Authority
  6. 6. How does it work? Anatomy of a DNS Lookup <ul><li>Your PC Asks: </li></ul><ul><li>Q: Where is www.cira.ca? </li></ul>
  7. 7. How does it work? Anatomy of a DNS Lookup <ul><li>Office-mail asks: </li></ul><ul><li>Q: Where is www.cira.ca? </li></ul><ul><li>A: I don’t know, but I can tell you who knows about .ca. </li></ul><ul><li>ca01.cira.ca </li></ul>
  8. 8. How does it work? Anatomy of a DNS Lookup <ul><li>Office-mail asks: </li></ul><ul><li>Q: Where is www.cira.ca? </li></ul><ul><li>A: I don’t know, but I can tell you who knows about .ca. </li></ul><ul><li>ca01.cira.ca </li></ul><ul><li>192.228.21.9 </li></ul>
  9. 9. How does it work? Anatomy of a DNS Lookup <ul><li>Office-mail asks: </li></ul><ul><li>Q: Where is www.cira.ca? </li></ul><ul><li>A: I don’t know, but I can tell you who knows about cira.ca. </li></ul><ul><li>ns01.cira.ca </li></ul><ul><li>192.228.22.70 </li></ul>
  10. 10. How does it work? Anatomy of a DNS Lookup <ul><li>Office-mail asks: </li></ul><ul><li>Q: Where is www.cira.ca? </li></ul><ul><li>A: It’s at 192.228.23.21 </li></ul>
  11. 11. How does it work? Anatomy of a DNS Lookup <ul><li>A: www.cira.ca is at 192.228.23.21 </li></ul>
  12. 12. How does it work? Anatomy of a DNS Lookup <ul><li>Your PC Asks: </li></ul><ul><li>Q: Where is www.microsoft.ca? </li></ul>
  13. 13. How does it work? Anatomy of a DNS Lookup <ul><li>Office-mail asks: </li></ul><ul><li>Q: Where is www.microsoft.ca? </li></ul><ul><li>A: I don’t know, but I can tell you who knows about .ca. </li></ul><ul><li>ca01.cira.ca </li></ul><ul><li>192.228.21.9 </li></ul>
  14. 14. How does it work? Anatomy of a DNS Lookup <ul><li>Office-mail asks: </li></ul><ul><li>Q: Where is www.microsoft.ca? </li></ul><ul><li>A: I don’t know, but I can tell you who knows about microsoft.ca. </li></ul><ul><li>ns4.msft.net </li></ul>
  15. 15. How does it work? Anatomy of a DNS Lookup <ul><li>Office-mail asks: </li></ul><ul><li>Q: Where is ns4.msft.net? </li></ul><ul><li>A: I don’t know, but I can tell you who knows about .net. </li></ul><ul><li>a.gtld-servers.net </li></ul>
  16. 16. How does it work? Anatomy of a DNS Lookup <ul><li>Office-mail asks: </li></ul><ul><li>Q: Where is ns4.msft.net? </li></ul><ul><li>A: I don’t know, but I can tell you who knows about msft.net. </li></ul><ul><li>ns4.msft.net </li></ul><ul><li>207.46.66.75 </li></ul>
  17. 17. How does it work? Anatomy of a DNS Lookup <ul><li>Office-mail asks: </li></ul><ul><li>Q: Where is www.microsoft.ca? </li></ul><ul><li>A: www.microsoft.ca is an alias for microsoft.ca. microsoft.ca has two IP addresses: 207.46.130.108 and 207.46.250.119. </li></ul>
  18. 18. How does it work? Anatomy of a DNS Lookup <ul><li>A: www.microsoft.ca is an alias for microsoft.ca. microsoft.ca has two IP addresses: 207.46.130.108 and 207.46.250.119. </li></ul>
  19. 19. How does it work? Anatomy of a DNS Lookup <ul><li>www.smallbusiness.ca hosted by hostingco.ca </li></ul><ul><li>hostingco.ca puts their customer domains on separate name servers from their own domain </li></ul>
  20. 20. How does it work? Anatomy of a DNS Lookup <ul><li>Q: Where is www.smallbusiness.ca? </li></ul><ul><li>A: I don’t know, but I can tell you who knows about smallbusiness.ca. </li></ul><ul><li>ns3.hostingco.ca </li></ul>
  21. 21. How does it work? Anatomy of a DNS Lookup <ul><li>Q: Where is ns3.hostingco.ca? </li></ul><ul><li>A: I don’t know, but I can tell you who knows about hostingco.ca </li></ul><ul><li>ns1.hostingco.ca </li></ul><ul><li>192.0.2.10 </li></ul>
  22. 22. How does it work? Anatomy of a DNS Lookup <ul><li>Q: Where is ns3.hostingco.ca? </li></ul><ul><li>A: ns3.hostingco.ca is at 192.0.2.8 </li></ul>
  23. 23. How does it work? Anatomy of a DNS Lookup <ul><li>Q: Where is www.smallbusiness.ca? </li></ul><ul><li>A: It’s at 192.0.2.81. </li></ul>
  24. 24. What if Something Breaks? Data Replication and Authority
  25. 25. What if Something Breaks? Dot-ca Data Replication
  26. 26. What Can The Data Say? Record Types <ul><li>Address Records (A) -- www.cira.ca is at 192.228.23.21 </li></ul><ul><li>Pointer Records (PTR) -- 192.228.23.21 is the address for www.cira.ca </li></ul><ul><li>Name Server Records (NS) -- ns01.cira.ca is a nameserver for cira.ca </li></ul><ul><li>Mail Exchanger Records (MX) -- mail.cira.ca handles mail for cira.ca </li></ul><ul><li>Canonical Name (CNAME) -- www.cira.ca is an alias for cira.ca (cira.ca is the canonical name of www.cira.ca) </li></ul>
  27. 27. What Does it Look Like? Sample .ca Zone Data <ul><li>microsoft.ca. IN NS ns1.msft.net. </li></ul><ul><li>IN NS ns2.msft.net. </li></ul><ul><li>IN NS ns3.msft.net. </li></ul><ul><li>IN NS ns4.msft.net. </li></ul><ul><li>IN NS ns5.msft.net. </li></ul><ul><li>webnames.ca. IN NS relay.cdnnet.ca. </li></ul><ul><li>IN NS ns1.cs.ubc.ca. </li></ul><ul><li>IN NS blackwidow.webnames.ca. </li></ul><ul><li>cira.ca. IN NS ns01.cira.ca. </li></ul><ul><li>IN NS ns02.cira.ca. </li></ul><ul><li>IN NS ns03.cira.ca. </li></ul><ul><li>relay.cdnnet.ca. IN A 192.73.5.1 </li></ul><ul><li>blackwidow.webnames.ca. IN A 207.232.123.229 </li></ul><ul><li>ns01.cira.ca. IN A 192.228.22.70 </li></ul><ul><li>ns02.cira.ca. IN A 192.228.22.71 </li></ul><ul><li>ns03.cira.ca. IN A 192.228.30.8 </li></ul>
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