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

 

URL Addresses:

• 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) :
host, second-level domain, top-level domain

 
 www.edinboro.edu
 cslab103.cs.edinboro.edu

Top-Level Domains (Examples)

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

Second-Level Domains (Examples)

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

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

cs.edinboro.edu
tac.edinboro.edu

 

URL (Uniform or Universal Resource Locator)

 *** also called the web page address

- consists of a   webserver name/path to web page

Static vs dynamic IP addresses

• every server has a static IP address listed with the registrar (static)
• a home machine may have an IP address that changes each time connected to the ISP (dynamic)

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 DNS Works

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:

• www.google.com
• www.yahoo.com
• www.dogpile.com
• www.altavista.com

Websites to checkout:

• How Can You Find Anything?
• Berkeley Internet Search Tutorials

Hobbes' Internet Timeline
A Brief History of the Internet