DNS 101 - What it is and how it works

DNS 101: What it is, how it works

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

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1984, Paul Mockapetris releases RFCs 882 and 883 (later superseded by 1034 and 1035); JEEVES released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

The DNS Tree Structure The Distributed Database

Who Manages What? Delegation of Authority

How does it work? Anatomy of a DNS Lookup
Your PC Asks:
Q: Where is www.cira.ca?

Office-mail asks:
A: I don’t know, but I can tell you who knows about .ca.
ca01.cira.ca

Office-mail asks:
ca01.cira.ca
192.228.21.9

Office-mail asks:
A: I don’t know, but I can tell you who knows about cira.ca.
ns01.cira.ca
192.228.22.70

Office-mail asks:
A: It’s at 192.228.23.21

A: www.cira.ca is at 192.228.23.21

Your PC Asks:
Q: Where is www.microsoft.ca?

Office-mail asks:
ca01.cira.ca
192.228.21.9

Office-mail asks:
A: I don’t know, but I can tell you who knows about microsoft.ca.
ns4.msft.net

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

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

Office-mail asks:
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.

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.

www.smallbusiness.ca hosted by hostingco.ca
hostingco.ca puts their customer domains on separate name servers from their own domain

Q: Where is www.smallbusiness.ca?
A: I don’t know, but I can tell you who knows about smallbusiness.ca.
ns3.hostingco.ca

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

Q: Where is ns3.hostingco.ca?
A: ns3.hostingco.ca is at 192.0.2.8

Q: Where is www.smallbusiness.ca?
A: It’s at 192.0.2.81.

What if Something Breaks? Data Replication and Authority

What if Something Breaks? Dot-ca Data Replication

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)

What Does it Look Like? Sample .ca Zone Data
microsoft.ca. IN NS ns1.msft.net.
IN NS ns2.msft.net.
IN NS ns3.msft.net.
IN NS ns4.msft.net.
IN NS ns5.msft.net.
webnames.ca. IN NS relay.cdnnet.ca.
IN NS ns1.cs.ubc.ca.
IN NS blackwidow.webnames.ca.
cira.ca. IN NS ns01.cira.ca.
IN NS ns02.cira.ca.
IN NS ns03.cira.ca.
relay.cdnnet.ca. IN A 192.73.5.1
blackwidow.webnames.ca. IN A 207.232.123.229
ns01.cira.ca. IN A 192.228.22.70
ns02.cira.ca. IN A 192.228.22.71
ns03.cira.ca. IN A 192.228.30.8

DNS 101 - What it is and how it works

by Canadian Internet Registration Authority on Oct 26, 2009

Accessibility

Categories

Tags

Upload Details

Usage Rights

1 Embed 37

Statistics

DNS 101 - What it is and how it works — Presentation Transcript