Computer Networks,Internet,& SMTP

Priyanka DaultaniDepartment of Computer

ScienceUSF, San Francsico, CA

What are Computer Networks?

• A computer network is an interconnected group of computers.

• Computer networking is the practice of linking two or more computing devices together for the purpose of sharing data.

• Examples:   LAN (by scale) ; Client Server network (by functional relationship)  etc.

• Internetwork: Any connection between two or more public, private, commercial , industrial etc networks is called a internetwork.

What is the Internet?

• The Internet is a type of an internetwork.• One of the many definitions:• Its a collection of computer networks, operating

worldwide, cooperating with each other to exchange data using a common software standard.

Uses of the Internet:

• Sharing research and business data.• Communicating with others and transmitting files via

E-mail. • Requesting and providing assistance with problems

and questions. • Marketing and publicizing products and services.• Gathering valuable feedback and suggestions from

customers and business partners.

Router/Switch Animation:

Here is how packets are transferred between a source and a destination:

http://static.howstuffworks.com/flash/router-lan.swf

Let us try this out amongst ourselves!

What is Email?

• E-mail is the short form for Electronic mail.• Email offers a fast, economical means of transferring

messages anywhere in the world. • What is an Email Client?• Components of an Email Client?

What is a Mail Server?

• It is the application that receives mail from the email client and from other mail servers.

Email over the internet:

Eg showing email over the internet:

What is a Protocol?

• A simple example: What do we say when we call someone using a cellphone?

• Standard definition of a protocol: A Protocol can be defined as the rules governing the syntax, semantics, and synchronization of communication.

SMTP: Simple Mail Transfer Protocol• Simple Mail Transfer Protocol (SMTP) is a standard

set of rules and procedures by which messages can be transferred over the Internet. is used by Mail Servers to send messages back and forth to other Mail Servers or Email Clients.

• List of SMTP commands:              HELO              RCPT  TO              MAIL  FROM              DATA              QUIT

POP: Post Office Protocol

• In order to collect email messages from the Mail Server, the Email Client contacts the Mail Server and supplies it with an account “user” name and a password.

• List of POP commands:              USER              PASS              STAT              RETR 1               DELE 1

SMTP and POP:

Images from: http://www.tekguard.com/Content/Software/Tutorials/EMailTutorial_P2.htm

Thank You!!

                             Questions???