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 Early 80’s: TCP/IP added to BSD, and ARPAnet growth explodes 1984, Paul Mockapetris releases RFCs 882 and 883 (later superseded by 1034 and 1035); JEEVES released 1985, Berkeley releases first version of BIND, written by Kevin Dunlap 1993, BIND 4.9 is released by DEC, managed by Paul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