CIT 307 OnlineData Communications

Domain Name SystemDomain Name System

Module 19Module 19Kevin Siminski, InstructorKevin Siminski, Instructor

Domain Name System (DNS)

DNS- database of databases! Correlation between IP address and a

domain name Name space can be flat or Hierarchical

Domain Name Space

Only 128 levels-– 0 is the Root level

Should be a structured or hierarchical environment

What would the internet be without DNS?

Domain Name space

Domain names and labels

FQDN and PQDN

Domains

Distribution of Name space(s)

Hierarchy of Name Servers Zone Root Server Primary and Secondary Servers

Hierarchy

Zones and domains

Root Servers

Heart of the Internet Currently, there are 13 root servers

worldwide

Primary and Secondary Servers

A primary server loads all information from the disk file; the secondary server loads all information from the primary server.

DNS and the Internet

Generic Domains

Generic domain labels

Label Description

com Commercial organizations

edu Educational institutions

gov Government institutions

int International organizations

mil Military groups

net Network support centers

org Nonprofit organizations

New Generic domain labels

Label Description

aero Airlines and aerospace companies

biz Businesses or firms (similar to com)

coop Cooperative business organizations

info Information service providers

museum Museums and other nonprofit organizations

name Personal names (individuals)

pro Professional individual organizations

County domains

Inverse domain

Resolution

Mappint a name to an address or an address to a name is called name-address resolution

Resolver- client/server application Mapping names to address Mapping addresses to names

Recursive resolution

Iterative Resolution

Port numbers

DNS can use the services of UDP or TCP,

using the well-known port 53.