DNS Notes Textbook

DNS Overview

19-1 Need for DNS

• TCP/IP protocols utilize IP addresses to uniquely identify a host's connection to the Internet.
• Users prefer using names instead of numeric addresses, leading to the necessity of a system that maps names to addresses and vice versa.

19-2 Name Space

• To avoid ambiguity, machine names must be chosen from a unique name space that links names to IP addresses.
• The organization of the name space can be:
  • Flat Name Space: Simple structure, lacks hierarchical organization.
  • Hierarchical Name Space: Structured with levels, makes it easier to manage large numbers of names.

Topics Discussed

• Flat Name Space
• Hierarchical Name Space
• Domain Name Space
• Domain
• Distribution of Name Space

Domain Name Space Structure

• The domain name space consists of different labels and domains:
  • Root Level: The starting point of the domain structure.
  • Examples of Labels: edu, com, org.
  • Sub-domains: For instance, fhda.edu breaks into atc.fhda.edu.

19-3 DNS in the Internet

• DNS serves various platforms and manages a divided domain name space with three main sections:
  • Generic Domains: e.g., com, edu
  • Country Domains: e.g., us, fr
  • Inverse Domain: Used for reverse lookups.

Generic Domain Examples

• Labels and Descriptions:
  • aero: Airlines and aerospace companies
  • biz: Businesses or firms
  • edu: Educational institutions
  • gov: Government institutions

19-4 Resolution

• The process of mapping a name to an address or an address to a name is termed name-address resolution.

Types of Resolution

1. Recursive Resolution: The client requests the address, and if the server cannot resolve it, it queries other servers until resolved.
2. Iterative Resolution: The client sends a request to the server, which provides the best-known response without further queries.

19-5 DNS Messages

• DNS involves two main types of messages:
  • Query Message: Includes header and question records.
  • Response Message: Comprises header, question records, answer records, authoritative records, and additional records.