Working of Internet:

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hellofriends...many of u ask questions like how internet works.so in thisarticle i m giving the easiest understanding of wrking of Internetusing two simple examples...

example 1 - what happens when u type a domain abc.com in ur browser.

example 2 -? what happens when u send mail at user@example.com

Example 1:

now u JUST don't type abc.com in ur browser do u see a simple most common step u do do is Connect Internet !!!

it looks common BUT it is imp...as when u connect to internet (generally)
uget the IP of the DNS resolvers nameservers...(ur ISP may configurethat but that is an uncommon setting so i m not including that here...)

now u got 2 nameservers which will resolve name abc.com for u to an IP

so now u can type abc.com ...:)

now as u type,a DNS query is generated.

DNS query-its AIM is here to resolve abc.com to *.*.*.* IP where * is from 0 to 255

Root of DNS query:

? Now ur ISP can give two answers a)i know the IP as it is in my cache.

?????????????????????????????????????????????????? b)i don't know?

NOW"i don't know" here means that it is not in cache BUT as ur ISPnamservers know the IP of 13 defined Root Nameservers so it willforward ur dns query to anyone of Root Nameserver depending upon whichis near and many other factors.

nowthey again forward dns query to Generic TLD servers i.e which knowabout the Authoritative Nameservers of any .com,.biz,.net and .org

so Generic servers return Nameservers as well as their IP (Glue records) to the dns query.

it can return these answers:

a)i know the IP as an A record...->end of quiry as IP of abc.com hd been returned

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b)idon't know IP but i have its NS records pointing to any other (may be)authoritative servers.so now query further routes and this go on untillquery ends ....i.e get A records or show up DNS error.

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c)itmay say abc.com is an alias of another domain xyz.com i.eabc.com->cname to xyz.com hence now query goes for xyz.com....andreturns the IP of xyz.com

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d)i don't know !!!?

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yes d) is an result of DNS misconfiguration.

hence we get IP for abc.com thus enabling our system to start transferring data using TCP as protocol.

Example 2

what happens when u send mail at user@abc.com

here again a DNS query is generated BUT from smtp servers of the email provider.

its AIM is to resolve abc.com and get the MX or Apex A record...(only in case MX is absent)

now e.g if it returns MX as?mx1.hostedmail.emailhost.com then this emailhost.com is furtherresolved and so on until the email provider gets the IP of receivingservers.

after getting IP of recieving servers the sender's mails servers transfers the data following SMTP as protocol.

Author Contact details:

Anurag Bhatia

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Email - me [at] anuragbhatia [dot] com

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IM-me [at] anuragbhatia [dot] com on Gtalk/MSN/AIM network.

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Voice mail/fax- +1-206-666-4078

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