Lectures notes for 2010 - KTH

DNS: Domain Name Service
(RFC 1034, RFC 1035)
• To make the network more user friendly
• Distributed database (with caching) providing:
• hostname ⇒ IP address, IP address⇒ hostname
• mailbox ⇒ mail server
• …
• applications call a “resolver”
• gethostbyname: hostname ⇒ IP address
• gethostbyaddr: IP address⇒ hostname
• Resolver’s contact name servers (see “/etc/resolv.conf”)
• DNS names:
• domain name: list of labels from a root, i.e., www.imit.kth.se
• Fully Qualified Name (FQDN): a domain name ending in “.” - there are no further labels
• leaves are managed locally through delegation of authority (to a zone) not centrally;
this allows scaling
• if a name server does not know the answer it asks other name servers
– every name server must know how to contact a root server
• Uses UDP (for query) and TCP (zone transfer and large record query)
Maguire DNS: Domain Name Service (RFC 1034, RFC 1035) 4: 44 of 74
maguire@kth.se 2010.03.21 Internetworking/Internetteknik