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Networking - DNS

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Lesson Description


Lession - #1384 DNS Protocol




The DNS protocol works when your computer sends out a DNS query to a name server to resolve a domain. For illustration, you type"www.firewall.cx" in your web browser, this triggers a DNS request, which your computer sends to a DNS server in order to get the website's IP Address! There's a detailed illustration on the pages to follow so I will not get into too important detail for the moment.

The DNS protocol normally uses the UDP protocol as a means of transport because of its small overhead in comparison to TCP; the less overhead a protocol has, the faster it's!

In the case where there are constant errors and the computer trying to request a DNS resolution can not get an error free answer, or any answer at all, it'll switch to TCP to ensure the data arrives without errors.

This process, though, depends on the operating system you are using. Some operating systems might not allow DNS to use the TCP protocol, therefore limiting it to UDP only. It's rare that you'll get so many errors that you can not resolve any hostname or domain name to an IP Address.

The DNS protocol utilises Port 53 for its service. This means that a DNS server listens on Port 53 and expects any client wishing to use the service to use the same port. There are, however, cases where you might need to use a different harborage, something possible depending on the operating system and DNS server you're running.