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DNS

DNS. By Ashish Suthar SDE (Information Tech.), RTTC, Ahmedabad. DNS. DNS stands for two things Domain Name Service (or Domain Name System) Domain Name Servers. One acronym defines the protocol; the other defines the machines that provide the service. What DNS do.

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DNS

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  1. DNS By Ashish Suthar SDE (Information Tech.), RTTC, Ahmedabad

  2. DNS • DNS stands for two things • Domain Name Service (or Domain Name System) • Domain Name Servers. • One acronym defines the protocol; the other defines the machines that provide the service.

  3. What DNS do • The job that DNS performs is very simple: it takes the IP addresses that computers connected to the Internet use to communicate with each other and it maps them to hostnames.

  4. History • DNS traces its origins to ARPANET. Alphabetic hostnames were introduced shortly after its inception as a means of allowing users greater functionality, since the numeric addresses proved difficult to remember.

  5. Top level domains • Top-level domains are at the root of the DNS hierarchy and are therefore also called root domains. These domains are organized geographically, by organization type, and by function.

  6. Three type of TLDs • Generic or Organization based TLD (e.g com, edu, gov, mil, net, org, int, aero, museum, etc) • Geographical or country based TLD (e.g. in, us, au, etc). This TLS is having 2 letters. • Inverse (e.g. arpa). This TLD is to find domain name from IP address.

  7. Sub-Domains • Sub-domains are often referred to as child domains. For example, the fully qualified domain name (FQDN) for a computer within a human resources group could be designated as jacob.hr.microsoft.com. Here, jacob is the host name, hr is the child domain, and microsoft.com is the parent domain.

  8. Components of DNS Domain Namespace Resource Records DNS servers DNS Clients

  9. Domain Namespace • An administrative domain is a group of computers in a single administrative unit. Each administrative domain has two or more name servers for name resolution. • All administrative domains registered with the Internet form a hierarchical structure, called the DNS domain namespace.

  10. Domain Namespace

  11. Top-Level Domains

  12. Second Level Domains • When an organization registers for the second-level domain, a top-level domain label is assigned based on the type of organization. • E.g example.com example is second level and com is a top level

  13. Resource Records (RRs) • Resource Records (RRs) store and map domain names to the type of resources stored within a domain. • Resource records contain information, such as the type, class, TTL, and RDATA. Domain Class Type IP TTL example.com IN A 172.154.129.12 8460

  14. DNS Server • Primary servers • Secondary Servers • Cache-Only servers

  15. Primary DNS Server • Stores the master copy of the domain-specific information. • Changes in the domain-specific information are updated on the primary name server. • As per the DNS design specification, each administrative domain should have two authoritative name servers. • One of the authoritative name servers is designated as the primary server.

  16. Secondary DNS Server • Stores the copy of the master data file stored in the primary name server. • Secondary name servers are delegated authority by the primary name server to perform name resolution. • Periodically it will collect the database information from the Primary server.

  17. Cache-Only Server • Stores the information received by the name servers in the memory till it expires. • This cached information is used to resolve queries. • A caching server that is not authoritative for a domain is called a cache-only server.

  18. DNS Clients • Name to address translation: DNS client translates user-friendly domain names to IP addresses. • Address to name translation: DNS client also translates IP addresses to user-friendly computer name. • General lookup function: DNS clients help end user programs to retrieve arbitrary information from a DNS server.

  19. Thanks • Any Question?

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