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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.