Presentation on Wit

8/9/2019 Presentation on Wit

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PRESENTATION ON WIT


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SIMPLE MAIL TRANSFER PROTOCOL(SMTP)y Simple Mail Transfer Protocol (SMTP) is

an Internet standard for electronic mail (e-mail)transmission across Internet Protocol (IP)

networks.y SMTP is specified for outgoing mail transport and

uses TCP port 25.


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y E lectronic mail servers and other mail transferagents use SMTP to send and receive mail messages,user-level client mail applications typically only useSMTP for sending messages to a mail serverfor relaying.

y For receiving messages, client applications usually useeither the Post Office Protocol (POP) or the InternetMessage Access Protocol (IMAP) or a proprietary

system (such as Microsoft Ex change or LotusNotes/Domino) to access their mail bo x accounts on amail server.


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MUA: Mail user agentMSA: Mail submission agentMTA: Mail transfer agentMDA: Mail delivery agentMX: Mail exchanger

MAIL PROCESSING MODE LBlue arrows can be implemented using SMTP variations.


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y The POP protocol has been developed through severalversions, with version 3 (POP3) being the currentstandard. POP3 is used for most webmail services suchas Gma il and Yah oo.

y POP uses the Transmission Control Protocol on portnumber 110. Transmission may be encryptedusing Transport Layer Security (TLS) or Secure SocketsLayer (SSL). This is negotiated in the POP3 protocol

using the STLScommand.


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y POP3 has become the most common email clientconnection protocol.

y The POP3 protocol enables any email programanywhere on the Internet to connect to any email

server to perform the usual email functions, such asreading and sending, as long as they have a validaccount and password.

y POP3 is an open Internet standard. The commonPOP3 commands and responses are listed in thefollowing table :


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Command Respo nses

getwelcome () Gets the greeting from the server.

user (username) Login with a username. If valid username, server willrespond with request for password.

pass_ (password) Send password. If valid, server response will be twonumbers, message count and mailbo x size.

stat () Get the mailbo x status. Response is two numbers,message count and mailbo x size.

list ([message]) Get list of messages. An option "message" getsinformation on a specific message.

retr (message) Get message number "message".

dele (message) Delete message number "message".rset () Remove all deleted message markings.

noop () No operation. Do nothing. Really. Needed in unusualprogramming situations.

quit () Quit. Commits all changes, unlocks the mailbo x , andends the server connection.


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HYPER TEXT TRANSFER PROTOCOL(HTTP)

y The Hy pertext Tr an sfer Protocol (HTTP) isan Application Layer protocol for distributed,collaborative, hypermedia information systems.

y H TTP is a request-response protocol standardfor client-server computing. In H TTP, a web browser,for e xample, acts as a client , while an applicationrunning on a computer hosting the web site acts asa server . The client submits HTTP requests to theresponding server by sending messages to it.


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TRANSMISSION CONTROL PROTOCOL (TCP/IP)

y The Tran sm issio n Con trol Protocol (TCP) is one of the core protocols of the Internet Protocol Suite. TCPis one of the two original components of the suite(the other being Internet Protocol, or IP), so theentire suite is commonly referred to as TCP/IP.

y W hereas IP handles lower-level transmissions fromcomputer to computer as a message makes its way

across the Internet, TCP operates at a higher level,concerned only with the two end systems. (forex ample a W eb browser and a W eb server).


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y B esides the W eb, other common applications of TCPinclude e-mail and file transfer. Among othermanagement tasks, TCP controls segment size, flowcontrol, and data e xchange rate .

y TCP is used e x tensively by many of the Internet's mostpopular applications, including the W orld W ide W eb(WWW ), E-mail, File Transfer Protocol, SecureShell, peer-to-peer file sharing, and some streaming

media applications.


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OSI REFERNCE MODEL

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