Computer network
- 2. Electronic mail: Electronic mail (e-mail) : Is a process by which digital information can be sent, received, forwarded, and stored using telecommunications networks. Using the Internet, e-mail can be transmitted outside of corporate networks. Messages can also be sent to bulletin boards. 2
- 3. E-mail; Email Email is a service which allows us to send the message in electronic mode over the internet. It offers an efficient, inexpensive and real time mean of distributing information among people. E-Mail Address Each user of email is assigned a unique name for his email account. This name is known as E-mail address. Different users can send and receive messages according to the e-mail address.
- 4. “⇨ The username and the domain name are separated by @ (at) symbol. ⇨ E-mail addresses are not case sensitive. ⇨ Spaces are not allowed in e- mail address. 4
- 5. E-mail Message Components ⇨ E-mail message comprises of different components: ⇨ E-mail Header ⇨ Greeting ⇨ Text ⇨ Signature. 5
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- 7. ⇨ The first five lines of an E-mail message is called E- mail header. The header part comprises of following fields: ⇨ From ⇨ Date ⇨ To ⇨ Subject ⇨ CC ⇨ BCC E-mail Header 7
- 8. ⇨ From ⇨ The From field indicates the sender’s address i.e. who sent the e-mail. ⇨ Date ⇨ The Date field indicates the date when the e-mail was sent. ⇨ To ⇨ The To field indicates the recipient’s address i.e. to whom the e-mail is sent. ⇨ Subject ⇨ The Subject field indicates the purpose of e-mail. It should be precise and to the point. ⇨ CC ⇨ CC stands for Carbon copy. It includes those recipient addresses whom we want to keep informed but not exactly the intended recipient. ⇨ BCC ⇨ BCC stands for Black Carbon Copy. It is used when we do not want one or more of the recipients to know that someone else was copied on the message. 8
- 9. ⇨ Greeting ⇨ Greeting is the opening of the actual message. Eg. Hi Sir or Hi Guys etc. ⇨ Text ⇨ It represents the actual content of the message. ⇨ Signature ⇨ This is the final part of an e-mail message. It includes Name of Sender, Address, and Contact Number. 9
- 10. ⇨ E-mail has prooved to be powerful and reliable medium of commmunication. Here are the benefits of E-mail: ⇨ Reliable ⇨ Convenience ⇨ Speed ⇨ Inexpensive ⇨ Printable ⇨ Global ⇨ Generality 10
- 11. 11 Reliable Many of the mail systems notify the sender if e-mail message was undeliverable. Convenience There is no requirement of stationary and stamps. One does not have to go to post office. But all these things are not required for sending or receiving an mail. Speed E-mail is very fast. However, the speed also depends upon the underlying network. Inexpensive The cost of sending e-mail is very low. Printable It is easy to obtain a hardcopy of an e-mail. Also an electronic copy of an e-mail can also be saved for records.
- 12. 12 Printable It is easy to obtain a hardcopy of an e-mail. Also an electronic copy of an e-mail can also be saved for records. Global E-mail can be sent and received by a person sitting across the globe. Generality It is also possible to send graphics, programs and sounds with an e-mail.
- 13. 13 Forgery E-mail doesn’t prevent from forgery, that is, someone impersonating the sender, since sender is usually not authenticated in any way. Overload Convenience of E-mail may result in a flood of mail. Misdirection It is possible that you may send e-mail to an unintended recipient. Junk Junk emails are undesirable and inappropriate emails. Junk emails are sometimes referred to as spam. No Response It may be frustrating when the recipient does not read the e-mail and respond on a regular basis.
- 14. 14 Disadvantages Apart from several benefits of E-mail, there also exists some disadvantages as discussed below: Forgery Overload Misdirection Junk No response
- 15. E-mail protocol ⇨ E-mail Protocols are set of rules that help the client to properly transmit the information to or from the mail server. Here in this tutorial, we will discuss various protocols such as ⇨ SMTP ⇨ POP ⇨ IMAP. 15
- 16. 16 SMPTP SMTP stands for Simple Mail Transfer Protocol. It was first proposed in 1982. It is a standard protocol used for sending e-mail efficiently and reliably over the internet. Key Points: SMTP is application level protocol. SMTP is connection oriented protocol. SMTP is text based protocol. It handles exchange of messages between e-mail servers over TCP/IP network. Apart from transferring e-mail, SMPT also provides notification regarding incoming mail. When you send e-mail, your e-mail client sends it to your e- mail server which further contacts the recipient mail server using SMTP client.
- 17. ⇨ IMAP ⇨ IMAP stands for Internet Message Access Protocol. It was first proposed in 1986. There exist five versions of IMAP as follows: ⇨ Original IMAP ⇨ IMAP2 ⇨ IMAP3 ⇨ IMAP2bis ⇨ IMAP4 ⇨ 17
- 18. E-mail operations Creating Email Account There are various email service provider available such as Gmail, hotmail, ymail, rediff mail etc. Here we will learn how to create an account using Gmail. Open gmail.com and click create an account. Now a form will appear. Fill your details here and click Next Step. 18
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- 21. 21 . Composing and Sending EmailBefore sending an email, we need to compose a message. When we are composing an email message, we specify the following things: Sender’s address in To field Cc (if required) Bcc (if required) Subject of email message Text Signature
- 22. 22 ⇨ Reading Email ⇨ Every email program offers you an interface to access email messages. Like in Gmail, emails are stored under different tabs such as primary, social, and promotion. When you click one of tab, it displays a list of emails under that tab. ⇨ In order to read an email, you just have to click on that email. Once you click a particular email, it gets opened. ⇨ The opened email may have some file attached with it. The attachments are shown at the bottom of the opened email with an option called download attachment.
- 23. Replying Email ⇨ After reading an email, you may have to reply that email. To reply an email, click Reply option shown at the bottom of the opened email. ⇨ Once you click on Reply, it will automatically copy the sender’s address in to the To field. Below the To field, there is a text box where you can type the message. ⇨ Once you are done with entering message, click Send button. It’s that easy. Your email is sent. 23
- 24. Forwarding Email ⇨ It is also possible to send a copy of the message that you have received along with your own comments if you want. This can be done using forward button available in mail client software. ⇨ The difference between replying and forwarding an email is that when you reply a message to a person who has send the mail but while forwarding you can send it to anyone. ⇨ When you receive a forwarded message, the message is marked with a > character in front of each line and Subject: field is prefixed with Fw. 24
- 25. Deleting Email If you don’t want to keep email into your inbox, you can delete it by simply selecting the message from the message list and clicking delete or pressing the appropriate command. Some mail clients offers the deleted mails to be stored in a folder called deleted items or trash from where you can recover a deleted email.
- 26. E-mail feature 26 the mail client comes with enhanced features such as attachment, address book, and MIME support. Here in this chapter we will discuss all of these features which will give you a better understanding of added feature of a mail client program.
- 27. Attachment 27 Ability to attach file(s) along with the message is one of the most useful features of email. The attachment may be a word document, PowerPoint presentation, audio/video files, or images. Addressbook Address Book Address book feature of a mail program allows the users to store information about the people whom they communicate regularly by sending emails. Here are some of the key features of an Address book: Address book includes the nick names, email addresses, phone number etc. of the people. Using address book allows us not to memorize email of address of a person, you just have to select recipient name from the list.
- 28. 28 MIME Types MIME is acronym of Multipurpose Internet Mail Extensions. MIME compliant mailer allows us to send files other than simple text i.e. It allows us to send audio, video, images, document, and pdf files as an attachment to an email.
- 29. TELNET 29 Telnet, developed in 1969, is a protocol that provides a command line interface for communication with a remote device or server, sometimes employed for remote management but also for initial device setup like network hardware. It is a used as a standard TCP/IP protocol for virtual terminal service which is given by ISO. Computer which starts connection known as the local computer. Computer which is being connected to i.e. which accepts the connection known as remote computer.
- 30. TELNET COMMANDS 30 Commands of the telnet are identified by a prefix character, Interpret As Command (IAC) which is having code 255. IAC is followed by command and option codes. Basic format of the command is as shown in the following figure :
- 31. Modes of operation 31 Modes of Operation : Most telnet implementation operates in one of the following three modes : Default mode Character mode Line mode
- 32. Default mode 32 Default Mode : If there is no other modes are invoked then this mode is used. Echoing is performed in this mode by client. In this mode, user types a character and client enchoes the character on the screen but it does not send it until whole line is completed.
- 33. Character mode& line mode 33 HIGH VALUE 1 LOW VALUE 2 Character Mode : Each character typed in this mode is sent by client to server. Server in this type of mode is normally enchoes character back to be displayed on the client’s screen. Line Mode : Line editing like echoing, character erasing etc is done from the client side. Client will send the whole line to the server.
- 34. Telnet uses 34 Telnet is a network protocol used to virtually access a computer and to provide a two-way, collaborative and text-based communication channel between two machines. It follows a user command Transmission Control Protocol/Internet Protocol (TCP/IP) networking protocol for creating remote sessions.
- 35. 35 There are two types of login: Local login When a user logs into a local computer, then it is known as local login. When the workstation running terminal emulator, the keystrokes entered by the user are accepted by the terminal driver. The terminal driver then passes these characters to the operating system which in turn, invokes the desired application program.
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- 37. 37 Remote login
- 38. At the local site The user sends the keystrokes to the terminal driver, the characters are then sent to the TELNET client. The TELNET client which in turn, transforms the characters to a universal character set known as network virtual terminal characters and delivers them to the local TCP/IP stack At the remote site The commands in NVT forms are transmitted to the TCP/IP at the remote machine. Here, the characters are delivered to the operating system and then pass to the TELNET server. The TELNET server transforms the characters which can be understandable by a remote computer.
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