The resolver determines which servers it should contact to ask a query. A client program asks for name service resolution by making calls to a library called the resolver. In DNS name resolution how do browsers determine the nearest DNS servers available among many DNS servers?Īs the other answers indicate, your browser, or other client program does not do this selection.

What makes you think any kind of ranging operation is going on? As long as it gets an answer in time, it recurses down from there. It'll be implementation-dependent, but afaict in my case (BIND), it just picks one and queries it. (which is usually periodically updated by querying an available root nameserver).Įdit: It doesn't.

It is the recursive-resolving nameservers in that chain (whether those be your locally-configured authoritative nameservers, or some ISP's servers down the line) that need to know how to find the root servers, and they do it via a pre-configured zonefile for. Note that most steps in the above chain are configurable, so what your browser does in fact will be locally-determined but the scenario above is typical. They will in turn either forward your desktop's OS's query to upstream servers (cacheing any reply) or perform recursive resolution themselves. Your browser will use the standard system calls for resolving hostnames (usually, I believe, getaddrinfo()), and these will in turn usually examine the contents of /etc/nf to find the configured resolving nameservers, and query them.

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