quartz/content/notes/11-DNS.md

title	tags
11-DNS	lecture cosc301

[!INFO] hosts are named by ip addresses: e.g., 192.168.1.2 we want to map an ip address to a readable name so it is memorable in the past it was easy to store all the name of possible address in a folder /etc/hosts. it uses a NIC networking inforamtion system. but this is only for LAN impossible to store all IP addresses in the internet this way

[!INFO] DNS resolves a name to an IP address. can also do reverse mapping (this is useful for detecting spam emails).

[!INFO] distributed dns now dns is distributed. it is a BIND (berkely internet name domain) service. to do something distributedly. each LAN has their own DNS

Problem

• How to get the IP address with an IP name?
  • Mapping between IP addresses and IP names
• Simple solution
  • Central database, like /etc/hosts or Sun
    Microsystems’ NIS (Network Information
    Service) or Windows’ WINS for LAN.
  • E.g. tkm.govt.nz 13.77.63.24
• However, keeping billions of such records
  in a central database used by billions of
  users is almost impossible.

Domain Name Service (DNS)

• A distributed solution
• Each organisation, called domain, maintains
  its own database and answers queries about
  its domain.
• E.g.
  • oucs1120.otago.ac.nz 139.80.22.10
  • oucs1234.otago.ac.nz 139.80.34.67
  • chasm.otago.ac.nz 139.80.45.90
  • hextreme.otago.ac.nz 139.80.63.88