Q.) Explain what happens, step by step, after you type a URL into a browser  Use as much detail as possible 


There’s no right, or even complete, answer for this question   This question allows you to go into arbitrary amounts of detail depending on what you’re comfortable with   Here’s a start though:

  1. Browser contacts the DNS server to find the IP address of URL
  2. DNS returns back the IP address of the site
  3. Browser opens TCP connection to the web server at port 80
  4. Browser fetches the html code of the page requested
  5. Browser renders the HTML in the display window
  6. Browser terminates the connection when window is closed

One of the most interesting steps is Step 1 and 2 – “Domain Name Resolution ”  The web ad-dresses we type are nothing but an alias to an IP address in human readable form   Mapping of  domain  names  and  their  associated  Internet  Protocol  (IP)  addresses  is  managed  by  the Domain Name System (DNS), which is a distributed but hierarchical entity .

Each domain name server is divided into zones   A single server may only be responsible for  knowing the host names and IP addresses for a small subset of a zone, but DNS servers can work  together  to  map  all  domain  names  to  their  IP  addresses    That  means  if  one  domain name  server  is  unable  to  find  the  IP  addresses  of  a  requested  domain  then  it  requests  the information from other domain name servers.

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