Domain Name System
DNS is a distributed database that contain mappings of DNS domain names to data. It’s also a protocol for transmission control Protocol/ Internet Protocol (TCP/IP) networks, defined by the Requests for comments (RFCs) that pertain to DNS. DNS associates various information with domain names assigns to each of the participating entities. DNS not only translates it also memorize domain name and co related IP Address new to that server. The internet maintain two principal namespaces, The domain name hierarchy and the Internet Protocol address spaces.
Domain Name Space
A Domain namespace is a name service provider by the Internet for Transmission Control Protocol / Internet protocol . DNS is broken up into domains ,a logical organization of computers that exist in a larger network . Domain name space are organized as Root of a tree . Each branch is a domain, each sub branch is a subdomain .
Even communication between user and host take up a few hundred milliseconds to send and receive any message or query but sometime server can response very slow due to huge traffic. The easy way to speed up this process is catch the information locally thereby eliminating the need for repetitive queries to the remote DNS server. This is done by connecting local database on your computer, rather than the remote DNS server. PostCast server contacts the remote DNS server once , and then caches (memorizes) the addresses returned from query . So the next time every request come for same domain address it instantly returns the answer ,without having to contact your ISP’s DNS server to ask it for translation .
The client side of the DNS is called a DNS resolver. A resolver is responsible for initiating the sequencing the queries that ultimate lead to a full resolution of resource sought. An Individual DNS query may be either non-recursive, or iterative or a combination of all these. For the non-recursive query method, a DNS resolver client queries a DNS server that provides a record for a domain for which it is authoritative itself, or it provides a partial result without querying other servers. In case of a caching DNS resolver, the non-recursive query of its local DNS cache delivers a result and reduces the load on upstream DNS servers by caching DNS request records for a period of time after an initial response from upstream DNS servers. For the recursive query approach, a DNS resolver client will query a single DNS server, which may then query ex rel. (as a client itself) other DNS servers as needed. For the iterative query procedure, a DNS resolver client will query a chain of one or more DNS servers. Each server will refer the client to the next server in the chain, until the current server can fully resolve the request
A reverse lookup is a query of the DNS for domain names when the IP address is known. Multiple domain names may be associated with an IP address. The DNS stores IP addresses in the form of domain names as specially formatted names in pointer (PTR) records within the infrastructure top-level domain ARPA.
Author : cialfor
Updated : 9/26/2016