[Ilugc] [OT] how does a Browser work?
peevee.chaitanya at gmail.com
Mon Apr 25 18:09:52 IST 2005
Binand Sethumadhavan wrote:
>On 25/04/05, peevee <peevee.chaitanya at gmail.com> wrote:
>>can anyone tell me how a browser typically works....
>>I mean, when i type a web address, how or where does it resolve the ip
>>for that name,
>>how does it know which server to contact for resolving it first??
>>later i know that the dns is resolved and the packets reaches the
>>respective server, and response comes accodingly,
>>all i want to know is , the initial part..
>Not just a browser, but any network-aware software does the initial
>Every TCP/IP "stack" has a subsystem called a resolver - your browser
>typically starts by asking the resolver to resolve a name into an IP
>address. The resolver consults a configuration file - /etc/resolv.conf
>on Unix - and asks the nameservers listed there (which is typically
>the IP address(es) of the nearest DNS cache) to resolve the name for
initially where does it get this nearest DNS cache from??
>it. The DNS cache performs a complex recursive lookup procedure, and
>extracts the IP address associated with the name, caches the result
>and tells your resolver what it got. The resolver in turn tells your
>application the IP address. Then the browser switches its attention to
>the socket subsystem of TCP/IP and tries to open a connection to the
>IP address it got thus.
>It is in reality somewhat more complicated (especially on Linux,
>Solaris etc.), because another layer of abstraction exists between the
>resolver and the application called Name Services. Depending on the
>configuration in /etc/nsswitch.conf, this layer decides whether to
>contact the resolver, the NIS database or simply your /etc/hosts to
>figure out what IP address is associated with a given name.
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