Domain Name System (DNS) is a database system that translates a computer’s fully qualified domain name into an IP address. Network computer use IP address to locate and connect to computers. What DNS servers do is it converts a user friendly name like Yahoo.com to a numeric IP address of 209.191.122.70. It is easier to for humans to remember the domain name that the IP address. Reverse DNS (rDNS) does just the opposite of DNS; it takes the IP address and converter it to friendly user names.
Any organization that maintains a computer network will have at least one Name server that handles the DNS queries. The name server holds a list of all IP address within the network, along with cache of IP address from other domain names. When a computer requests an IP address there is three things that can happen.
1. If the request is a local IP address then the request goes to the Name server that is configured on you work station. Your response will be quickly almost instantly.
2. If the request is not one of the local address, but someone in the network has requested the information recently. The request will be for filled from the cache on the name server. Then you will receive you information will be a quit response.
3. If the request is not a local IP address, and no one has requested the IP address. The name server will perform a search on behalf of the workstation this search may involve querying two or more other name servers at are at remote locations. These queries can take anywhere from a second or two up to a minutes.
If you are trying to get to a website and you keep getting an error message your DNS may have old data. The website may have had changes and the cache in your DNS server needs to be cleared. It is import to clear the cash in the name server for this reason.
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