DNS Queries: A means to improve performance of carrier networks
All sites, including social networking sites on the Internet make use of DNS queries.
Whenever a client requests an IP address for a particular domain name, a query is sent to the DNS server to resolve the name. A DNS query usually contains the type of query, the fully qualified domain name (FQDN) and a particular class for the domain name of the DNS.
For example, if a host sends a DNS query for abc.mynetwork.com as shown in Figure () , the local DNS server verifies its record to find the IP address and sends it back with the IP address 10.1.2.5.102 for example.
If the host requests name resolution for www.abc.com and the host is found in the DNS server’s zone data and there is no record for the local DNS related to the requested domain name, the local DNS server tries to resolve the domain name to its IP address by using:
• Iterative search/query
• Recursive search/query
Whenever a DNS client sends a recursive query to a local name server, the server tries to resolve the name with complete answers or with an error by following the hierarchy of names all the way to the authoritative name server. The client which has made the request for queries receives address details only from the local name server.
The local name server makes requests to other DNS servers in the network for the client. However when it receives an iterative query, a search for the DNS information is done by the local name server within its records. If the local name server does not contain information about that specific DNS within itself, it refers to another name server for the client to go to next.
Example of a local DNS server performing iterative DNS query.
In this example, the local server keeps on referring to other DNS servers and sends the query repeated times to the other DNS until the query is resolved.
Example of a local name server performing recursive query where client always receives response from local name server.