chapter 25. domain name system
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Fall 2006 Computer Networks 25-1
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
Fall 2006 Computer Networks 25-2
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
Fall 2006 Computer Networks 25-6
Hierarchy of name servers
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Zones and domains
• Zone: What s server is responsible for, or has authority over
Fall 2006 Computer Networks 25-8
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.
Fall 2006 Computer Networks 25-9
DNS in the Internet
Fall 2006 Computer Networks 25-10
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
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