Remote Logging, Electronic Mail, and File Transfer Study Notes

  • TELNET is a client/server application that allows a user to log on to a remote machine, giving the user access to the remote system.
  • TELNET uses the network virtual terminal (NVT) system to encode characters on the local system. On the server machine, NVT decodes the characters to a form acceptable to the remote machine.
  • NVT uses a set of characters for data and a set of characters for control.
  • In TELNET, control characters are embedded in the data stream and preceded by the interpret as control (lAC) control character.
  • Options are features that enhance the TELNET process.
  • TELNET allows negotiation to set transfer conditions between the client and server before and during the use of the service.
  • A TELNET implementation operates in the default, character, or line mode. 1. In the default mode, the client sends one line at a time to the server. 2. In the character mode, the client sends one character at a time to the server. 3. In the line mode, the client sends one line at a time to the server.
  • Several programs, including SMTP, POP3, and IMAP4, are used in the Internet to provide electronic mail services.
  • In electronic mail, the VA prepares the message, creates the envelope, and puts the message in the envelope.
  • In electronic mail, the mail address consists of two parts: a local part (user mailbox) and a domain name. The form is localpart@domainname.
  • In electronic mail, Multipurpose Internet Mail Extension (MIME) allows the transfer of multimedia messages.
  • In electronic mail, the MTA transfers the mail across the Internet, a LAN, or a WAN.
  • SMTP uses commands and responses to transfer messages between an MTA client and an MTA server.
  • The steps in transferring a mail message are 1. Connection establishment· 2. Mail transfer 3. Connection termination
  • Post Office Protocol, version 3 (POP3) and Internet Mail Access Protocol, version 4 (IMAP4) are protocols used for pulling messages from a mail server.
  • One of the programs used for file transfer in the Internet is File Transfer Protocol (FTP).
  • FTP requires two connections for data transfer: a control connection and a data connection.
  • FTP employs NVT ASCII for communication between dissimilar systems.
  • Prior to the actual transfer of files, the file type, data structure, and transmission mode are defined by the client through the control connection.
  • Responses are sent from the server to the client during connection establishment.
  • There are three types of file transfer: 1. A file is copied from the server to the client. 2. A file is copied from the client to the server. 3. A list of directories or file names is sent from the server to the client.
  • Anonymous FTP provides a method for the general public to access files on remote sites.


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