DNS

DNS

• 1.
  Domain name System(DNS)
• 2.
  Domain Name System DomainName System,  Used to translate host names into host addresses.  Domain Name System (DNS) is not an application that users normally invoke explicitly, but rather a service that almost all other applications depend upon.  Addresses are not user friendly, so unique host name is also provided to the host in the network. Host names differ from host addresses in two important ways, Host name is usually of variable length and mnemonic, thereby making them easier for humans to remember. Host names typically contain no information that helps the network to locate (route packets toward) the host.
• 3.
  Domain Name System NameService (DNS) Name Space, Defines the set of possible names. It can be flat (not divisible in to components) or hierarchical. The naming system maintains a collection of bindings of names to values. The value can be anything we want the naming system to return when presented with a name; in many cases it is an IP address. A resolution mechanism is a procedure that, when invoked with a name, returns the corresponding value. A name server is a specific implementation of a resolution mechanism that is available on a network and that can be queried by sending it a message.
• 4.
  Domain Name System
• 5.
  Domain Name System DomainHierarchy DNS implements a hierarchical name space for Internet objects. DNS names are processed from right to left and use periods (Usually dot operator) as the separator. Like the Unix file hierarchy, the DNS hierarchy can be visualized as a tree, where, • Nodes – domain • Leaves – host
• 6.
  Domain Name System NameServers Hierarchy Implemetation, Partition the hierarchy into sub trees called zones. Each zone can be thought of as corresponding to some administrative authority that is responsible for that portion of the hierarchy. the top level of the hierarchy forms a zone that is managed by the Internet Corporation for Assigned Names and Numbers (ICANN). Each name server implements the zone information as a collection of resource records. In essence, a resource record is a name-to-value binding, or more specifically a 5-tuple that contains the following fields: <Name, Value, Type, Class, TTL > • Name – name of the host • Type - specifies how the Value should be interpreted.
• 7.
  Domain Name System PossibleTypes,  A – indicates value field contains an IP Address.  NS - The Value field gives the domain name for a host that is running a name server that knows how to resolve names within the specified domain.  CNAME: The Value field gives the canonical name for a particular host; it is used to define aliases.  MX: The Value field gives the domain name for a host that is running a mail server that accepts messages for the specified domain.
• 8.
  Domain Name System