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Chapter 25.Domain Name System

25.1 Name Space25.2 Domain Name Space25.3 Distribution of Name Space25.4 DNS in the Internet25.5 Resolution25.6 DNS Message25.7 DDNS25.8 Encapsulation

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Domain name space

• Flat name space, Hierarchical name space

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Domain names and labels

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FQDN and PQDN

• FQDN (Fully Qualified Domain Name)

• PQDN (Partially Qualified Domain Name)

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Domains

• Domain: Subtree of the domain name space

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Hierarchy of name servers

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Zones and domains

• Zone: What s server is responsible for, or has authority over

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Root Server

• A root server is a server whose zone consists of the whole tree.

Primary and Secondary Servers

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

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DNS in the Internet

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Generic domains

• Generic domains define registered hosts according to their generic behavior

• Each node in the tree defines a domain, which is an index to the domain name space database.

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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

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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

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Country domains

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Inverse domain

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Resolution

• Name-address resolution: a name to address/an address to a name

• Resolver: DNS client called by a host

• Recursive resolution and iterative resolution

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Iterative resolution

Caching

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Query and response messages

• DNS has two types of messages

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Header format