Understanding the Internet

Protocols Internet Protocols (TCP/IP)

What are protocols? A way to overcome communication differences

TCP: Transmission Control Protocol
Controls the form and route that data takes going across the network

IP: Internet Protocol
Handles the addressing of Internet computers

Application protocols:

HTTP: Hypertext Transfer Protocol
FTP: File Transfer Protocol
Telnet: Terminal Emulation Protocol

 

IP address

When an organization connects to the Internet, it obtains a set of IP addresses for its computers made up of 4 sets of numbers separated by periods or "dots"

  www.edinboro.edu:            147.64.32.6
  www.eupcs.org:                147.64.242.60
  cslab100.cs.edinboro.edu:  147.64.242.100
  www.spidermonkeys.com:  208.43.108.170

 

URL Addresses

(Uniform or Universal Resource Locator)

 *** also called the web page address

  • Easier to remember alphabetic names
  • Numeric addresses have corresponding canonical names so that you don't have to remember the numeric addresses.  
  • But the URL address must be converted to an IP address before the web page can be found on the Internet.
     

Minimum of 3 parts (usually 3-5) :

http://users.edinboro.edu:80/zimmer?doc=57&lang=en#middle

  • The protocol is http. Other protocols include https, ftp, etc.
  • The host or hostname is users.edinboro.edu
  • The subdomain is users
  • The domain name is edinboro.edu
  • The top-level domain or TLD is edu
  • The second-level domain (SLD) is edinboro.edu
  • The port is 80, which is the default port for web servers. Other ports are possible; a web server can listen on port 8000, for example. When the port is 80, most people leave out the port.
  • The path is /zimmer. Path typically refers to a file or location on the web server, e.g. /directory/file.html
  • This URL has parameters. The name of one parameter is doc and the value of that parameter is 57. URLs can have lots parameters. Parameters start with a question mark (?) and are separated with an ampersand (&).
  • The "#middle" is called a fragment or a named anchor. Typically the fragment is used to refer to an internal section within a web document.

 

Top-Level Domains (TLD)

 com: commercial organizations
 org: other organizations
 net: network resources
 gov: governmental organizations
 edu: educational organizations
 mil: military resources
 jp, nl, uk, ca, etc: country code TLD


Second-Level Domains (SLD)

edinboro.edu
php.net
w3.org
spidermonkeys.com


Subdomain/subnet Names

 Not always present
 Used when an organization divides their network into discrete parts

cs.edinboro.edu
users.edinboro.edu


Port number

  • A port number is given to each service on a web server that is available (like an extension on a phone line).
  • When a message is sent to a web server the port number is indicated either by the program sending it or by the user specifying it directly.
  • Many programs (server programs or services) are running all the time waiting for a request to come via the network and the port number determines which program intercepts the message
  • Port numbers and the program that receives the request:

echo 7
daytime 13
qotd 17 (Quote of the Day)
ftp 21
telnet 23
smtp 25 (Simple Mail Transfer, meaning email)
time 37
nameserver 42
nicname 43 (Who Is)
gopher 70
finger 79
WWW 80

How the internet works How stuff works:
searching the Internet Search Engines -

An attempt to automatically classify the web pages available:

  • A crawler (or spider) is a program that travels the web looking for web pages.
  • An indexer program reads these files and creates an index based on the words contained in each document.
  • When you submit a query (keyword search) the index is searched for the web pages that come closest to matching your search item.

 

Web Indexes -

Provides a directory structure to assist your searching.

 

Common websites for searching:

Website to checkout:

Evaluating a
website
Five Criteria for Evaluating Websites

Evaluation video
 

History Internet Timeline
 1969: ARPANET
 1971: First Email
 1972: Telnet
 1973: FTP
 1977: First mailing list
 1979: Usenet, MUD
 1981: BITNET, CSNET
 1982-83: TCP/IP
 1984: DNS
 1986: NSFNET, Freenet
 1990: ARPANET ends, ST&D's The World starts
 1991: Gopher, WWW
 1992: Veronica
 1993: Mosaic
 1994: Netscape
 1995: Java
 1998: XML
 2000: Napster law suit
 2003: SQL slammer worm takes down 5 of 13 DNS
 2005: Estimated 70 million host web servers on the Internet

*** see these sites for more:

Hobbes' Internet Timeline
A Brief History of the Internet