If someone could explain me the process of web browsing, the whole name look up, resolving, etc. I have tried to understand it, but I need it in common words, such as pleaseremove so well explains.

I enter http://www.foobar.com.

What happens next, step by step?

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so, you enter http://www.foobar.com into yoru browser and
1) yoru computer looks in its local cache file to see if it already knows the IP address. this file is the windows/system32/drivers/ect/hosts.txt file

if your computer knows the IP address jump to Section 8

2) your computer does not know the IP address, so it needs to ask someone, now when you connect to a network like the internet, you get given the ip address of a DNS (dynamic naming service) server, so you go and ask this dns server if it knows the ip address for http://www.foobar.com. it looks in its local cache file

if teh dns server knows the IP address then goto section 7

3) if the dns server doesnt know the ip of http://www.foobar.com it then handles the rest of teh asking for you, DNS servers have a list of "Root Hints" this is a list of other Root DNS servers where it can go ask for help finding an ip address. so you dns server goes and asks a root dns server, "do you know the ip address of http://www.foobar.com?"  

4) now the root dns server doesnt have a list of every site on the net, it has a list of ip addresses for servers handling teh top level domian names .com .uk .org .biz etc etc. so the root dns server replies to your dns server and says, "i dont knwo the address for http://www.foobar.com, but i do know that xxx.xxx.xxx.xxx knows about all the sites in the .com domain, go speak to him"

5) so now yoru dns server goes and speaks to the .com domain dns server, and asks if he knows, he looks at his local files and he replies, "no, i dont know who 'www.foobar.com' is, but i do know the ip of teh dns server that handles 'the foobar.com' domain

6) so now your nds server goes and speaks to the foobar.com dns server, and asks, and teh foobar.com server looks at his local files and finds a CNAME record,  

a CNAME record is a record that says the the computer known as 'www' is really called 'web1'

so the foobar.com dns server then looks in its records again and finds the record for the computer named 'web1' to which is has the ip address for (xxx.xxx.xxx.xxx)

so now the foobar.com dns server tells yoru dns server that it does know teh ip address of http://www.foobar.com and its it xxx.xxx.xxx.xxx

7) now yoru dns server tells you, yes i knwo the ip address of http://www.foobar.com it is xxx.xxx.xxx.xxx

8) your computer then connects to ip xxx.xxx.xxx.xxx

it uses the standard http protocal port of 80 and retrives teh website for you

ManicD
Microsoft Certified System Administrator

Post edited at 10:48 am on July 23, 2008 by ManicD

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