Cracking the Coding Interview, 4 Edition - 150 Programming Interview Questions and Solutions

Solutions to Chapter 17 | Networking
17.1 Explain what happens, step by step, after you type a URL into a browser. Use as much
detail as possible.
SOLUTION
pg 84
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 addresses
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.
2 4 9
Cracking the Coding Interview | Knowledge Based