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CNT 4713 Lecture Notes - Lecture 5: Message Transfer Agent, Dns Spoofing, Post Office Protocol

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School
FIU
Department
Computer Networks
Course
CNT 4713
Professor
Downey

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Document Summary

Mail server = client and host : receives and send messages. Uses tcp to reliably transfer email message from client to server, port 25. Direct transfer: sending server to receiving server. S: 250 hello crepes. fr, pleased to meet you. S: 354 enter mail, end with ". " on a line by itself. Smtp requires message (header & body) to be in 7-bit ascii. Smtp server uses crlf. crlf to determine end of message. Pop: post office protocol [rfc 1939]: authorization, download. Imap: internet mail access protocol [rfc 1730]: more features, including manipulation of stored msgs on server. How we send and receive data from layer below: Door between application process and end-end-transport protocol. In udp: no connection between client & server. Sender explicitly attaches ip destination address and port # to each packet. Rcvr extracts sender ip address and port# from received packet. Udp: transmitted data may be lost or received out-of-order.

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