We want resources to be accessible by meaningful names (i.e. usable by humans) rather than IP addresses - map IP address to name, vice versa.

• e.g. translate URL into IP

These mappings are done via DNS.

DNS Overview/Architecture

Domain Name System (DNS) is:

• Distributed database implemented in hierarchy of many name servers
• Application-level protocol where hosts and DNS servers communicate to resolve names (i.e. perform an address/name translation)
• A core Internet function implemented as an application-layer protocol
• Only runs at edge of network - not “core” of router/switches - transparent
• Runs on port 53

Services of DNS include:

• hostname to IP address translation
• host aliasing via canonical and alias names
• mail server aliasing
• load distribution via many IP addresses corresponding to a single name - give addresses in random order to balance load across machines

DNS is not centralized due to scalability reasons:

• Avoid single point of failure