The Different Parts
of a Domain Name

http://www.example.com:80/test.php?fname=James&lname=Hoff#lesson_1

Who am i?

Why are we discussing this again?

• Because we work on the Internet and use web browsers every day.  You will deal with domain names and URLs in some fashion every day.
  
  

• Because if I show you a really long and complicated URL, you should be able to identify its different parts and their meaning.
  
  

• Because you should be able to identify a legitimate URL vs. a phishing or SPAM URL.

is a domain name the same as a URL?

• NO!

• This is a URL  (Uniform Resource Locator):

  http://www.example.com/

• The "domain name" portion of that URL is:

  www.example.com

• A URL always includes a protocol like:
  

  http://
  ftp://
  

OK, So what exactly is a domain name?

• A domain name is really just a pointer to an IP address.

• When you see this in your browser's address bar:
  

  http://www.example.com/

  ...your browser sees this:
  

  http://76.12.220.208/

• Behind the scenes there is a domain name "phone book" that maps your requested domain name to the IP address of the server where the website lives.
  

  www.example.com   =>   76.12.220.208
  

Enough of that, let's talk anatomy

http://www.example.com:80/test.php?fname=James&lname=Hoff#lesson_1

• When it comes to websites, all that really matters is whether the protocol is:
  • https (secure connection)
  • http (non-secure connection)

• The protocol dictates which set of rules the browser and the web server use to communicate with and understand each other.

• Always followed by these characters: ://

Anatomy of the domain name itself

www.example.com

www.example.com

www.example.com

Top level Domain

http://www.example.com:80/test.php?fname=James&lname=Hoff#lesson_1

• Sometimes called an "extension."

• Most common TLDs:
  • .com
  • .net
  • .org
  • .edu

• Can also be country specific:
  • .au (Australia)
  • .ca (Canada)
  • .de (Germany)

second level domain

http://www.example.com:80/test.php?fname=James&lname=Hoff#lesson_1

• This is the "name" that you register and pay for in conjunction with the TLD.
  

  example.com
  example.net
  example.biz
  

• Can be up to 63 characters long.

• Good luck registering the name you want!!

Subdomain

http://www.example.com:80/test.php?fname=James&lname=Hoff#lesson_1

• A subdomain, by definition, is just a domain that is part of a larger domain.  They are optional.

• They do NOT need to be "registered." They are created entirely at the user's discretion. I can create any subdomain I want, for the second level domain that I registered, as long as it doesn't exceed 63 characters.

• Some subdomain examples in use at Google:
  

  mail.google.com
  maps.google.com
  images.google.com
  plus.google.com
  drive.google.com
  

Port Number

http://www.example.com:80/test.php?fname=James&lname=Hoff#lesson_1

• Seeing a port number in a URL is so rare that I'm only mentioning it for the sake of completeness.

• The default port for a non-secure (http) connection is 80.

• The default port of a secure (https) connection is 443.

• For all intents and purposes a port number only needs to specified in the URL if you're trying to connect to a port that IS NOT the default.

File/script name

http://www.example.com:80/test.php?fname=James&lname=Hoff#lesson_1

• This is the name of the document file requested.

• Normally an actual file on the server such as an HTML document, PHP script, JPG image, PDF document, etc. It can also be a folder name.

Query string

http://www.example.com:80/test.php?fname=James&lname=Hoff#lesson_1

• A query string is the part of a URL that contains data to be passed to web applications such as PHP scripts.

• Always starts with a question mark (?). Each name/value pair (parameter) thereafter separated by an ampersand (&).

• Usually generated by a web form or a script that communicates with a database.

Fragment

http://www.example.com:80/test.php?fname=James&lname=Hoff#lesson_1

• The fragment is optional but if it exists it always appears last and is set apart with a hash mark ( # ).

• The fragment identifier specifies a location within the HTML document. The browser looks for a tag with a "name" or "id" attribute matching the fragment.

  <h1 id="lesson_1">Lesson One: URL Anatomy</h1>

• Fragments are useful because they don't cause a page reload but they DO create an entry in the browser history.

That's all the anatomist wrote!

Now let's talk about the DARK SIDE of URLs.

phishing URLs

• There are mean people out there who manipulate URLs in a malicious manner in effort to trick you or steal from you.

• 99% of the time these URLs are found in SPAM emails called "phishing" emails.

• Examples of phishing URLs for PayPal:
  

  http://www.secure-paypal.com/
  http://www.paypal.signin.com/
  http://login.paypal.com.ag/
  http://214.34.17.132/paypal/
  http://www.paypal.com@214.34.17.132/login/
  http://www-paypal.com
  

phishing urls continued…

• Hyperlinks can also be manipulated in such a way that it looks like you're going to a website that you're NOT actually going to.

• If you're suspicious of a hyperlink, hover over it and look at your browser's status bar which will tell you the link's destination.

• Remember how we examined our domain name right to left a little while ago? That's standard procedure for visually parsing domain names to determine if they're legit. Find the first forward slash (/) and work backwards identifying the TLD, second level domain, etc.

• As a policy, "Don't call me, I call you!"

Thanks!