TCPIP Server Protocols

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TCP/IP Server Protocols

• version 05/25/2001

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History of TCP/IP 1973 Summer

• That summer the two of them worked out a proposal
  on a "Protocol for Packet Network
  Inter-communication". They described the new
  protocol like an envelope that carries parts of a
  letter inside, were the broken up letter are
  called "datagrams." It didnt mater to any
  network what was inside the letter, only that the
  envelope reaches its destination in one piece,
  if it didnt, a new letter would be sent. The new
  protocol, which would be essential for networks
  to communicate with each other, was called the
  Transmission-Control Protocol (TCP).

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History of TCP/IP 1973 _at_

• The famous _at_ symbol in every email address was
  created in 1973 by Ray Tomlinson at BBN. He was
  working to send messages over the ARPAnet. He
  developed SNDMSG and the first File Transfer
  Protocol called CPYNET which would send
  electronic messages over the ARPAnet. Tomlinson
  had to separate the user name from the computer
  name. He looked at his Model 33 Teletype and
  chose the _at_ symbol as the separator. By 1977, BBN
  used the Transmission Control Protocol (TCP) for
  the first time on a UNIX system.

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Send a DATAGRAM

• TCP/IP is a connectionless service. This means
  that when a large block of data is broken up into
  smaller pieces (datagrams) and sent to another
  host, the network is not aware that these
  individual datagrams are all related to each
  other. Datagrams often take different routes and
  arrive in different orders than those in which
  they were sent. TCP is well equipped to put all
  the datagrams back together, in the right order
  and in the right data block.

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TCP/IP Functions

• Computer Mail
• File Transfer
• Remote Login
• Network File Systems
• Remote Printing
• Remote Execution
• Name Servers
• Terminal Servers

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Simplified Protocol Stack
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TCP/IP Layer 4

• Layer 4 - Application - End-user applications
  reside at this layer. Gets data from the
  transport layer (UDP and TCP) by binding to
  ports.
• TCP examples include ftp, telnet, smtp, pop,
  imap http, nntp
• UDP examples include dns, rip, nfs, snmp,
  dhcp/bootp

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Stream Socket - TCP

• Provides for the bi-directional, reliable,
  sequenced, and unduplicated flow of data without
  record boundaries. A pair of connected stream
  sockets provides an interface nearly identical to
  that of pipes.

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SMTP

• Most e-mail is sent using Simple Mail Transport
  Protocol (SMTP). This Internet protocol exchanges
  ASCII messages (plain text, 7-bit) between two
  computers, a client and a server. SMPT is a
  "well-known service", virtually all mail servers
  run an SMTP server process which listens on port
  25, the standard SMTP port.

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SMTP RFC 821

• August 1982
• http//www.faqs.org/rfcs/rfc821.html

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Telnetting into SMTP

• telnet roicorporation.com 25220 X1 NT-ESMTP
  Server web1.roiconnect.com (IMail 5.05
  19836-1)helo ira_at_roicorporation.com250 hello
  web1.roiconnect.commail from ira_at_roicorporation.
  com250 okrcpt to katy_at_toottoot.com250 ok its
  for

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Composing the Message

• data354 ok, send it end with .from
  Irato katysubject Howdy!I love you!.
• 250 Message queued quit221 web1.roiconnect.com
  closing connection.

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SMTP Commands

• helo x Who I am xhost's FQDNsmtp_auth
  Do authenticationstart_tls Start TLS, secure
  connectmail from x Email from xaddressrcpt
  to x Receiver of emaildata Begin the
  message. End the current messagequit
  End this session

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MIME

• Internet e-mail standards, STD 11, RFC 822, were
  established in 1982. State of the art then, they
  have begun to show their age. Mail messages can
  contain a single human readable message with the
  restrictions
• only seven-bit ASCII characters.
• no lines longer than 1000 characters
• does not exceed a certain length

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MIME is Born

• The 1982 standards do not allow EDI to be
  reliably transmitted through Internet e-mail,
  since EDI messages can violate all of these
  restrictions. A new Internet mail standard was
  approved in June of 1992 called MIME. MIME is an
  acronym for Multipurpose Internet Mail
  Extensions
• It builds on the older standard by standardizing
  additional fields for mail message headers that
  describe new types of content and organization
  for messages.

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MIME Capabilities

• Multiple objects in a single message.
• Text having unlimited line length or overall
  length.
• Character sets other than ASCII, allowing
  non-English language messages.
• Multi-font messages.
• Binary or application specific files.
• Images, Audio, Video and multi-media messages.

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MIME Extensible

• MIME is an extensible mechanism. The set of
  content-type/subtype pairs and their associated
  parameters will grow with time. Several other
  MIME fields are likely to have new values defined
  over time. To ensure that the set of such values
  develops in an orderly, and public manner, MIME
  defines a registration process that uses the
  Internet Assigned Numbers Authority (IANA) as a
  central registry for such values.

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MIME

• MIME stands for Multipurpose Internet Mail
  Extension, a standard system for identifying the
  type of data contained in a file based on its
  extension. MIME is an Internet protocol that
  allows you to send binary files across the
  Internet as attachments to e-mail messages
  graphics, photos, sound and video files, and
  formatted text documents.

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MIME Across Platforms

• MIME negotiates many different operating systems
  and types of software to perform this amazing
  feat. Its invention has been a major step forward
  in the exchange of non-text information over the
  Internet.

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POP Server

• A POP server uses the Post Office Protocol, to
  hold users' incoming e-mail until they read or
  download it.

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Telnetting into POP

• Telnet to port 110, the POP port.
• c\ telnet roicorporation.com 110
• Terminal Preferences Local Echo

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POP

• telnet roicorporation.com 110OK X1 NT-POP3
  Server web1.roiconnect.com (IMail 5.08
  7054-1)user iraOK send your passwordpass
  foobarOK ira has 2 message(s) (1,344 octets).
• ...

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POP Commands

• USER uid Log in as "uidPASS pwd Use your
  password for "pwd"STAT List msg , total box
  sizeLIST List messages and sizesRETR n
  Show message nDELE n Mark message n for
  deletionRSET Undo any changesQUIT
  Logout, del msgs if no RSET
• More commands (and the entire spec) are available
  at http//www.imc.org/rfc1939.

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POP Version 3

• The Post Office Protocol - Version 3 (POP3) is
  intended to permit a workstation to dynamically
  access a maildrop on a server host in a useful
  fashion. Usually, this means that the POP3
  protocol is used to allow a workstation to
  retrieve mail that the server is holding for it.
• POP3 is not intended to provide extensive
  manipulation operations of mail on the server
  normally, mail is downloaded and then deleted. A
  more advanced (and complex) protocol, IMAP4, is
  discussed in RFC1730.
• http//www.faqs.org/rfcs/rfc1939.html

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IMAP

• http//www.isi.edu/in-notes/rfc2060.txt
• IMAP stands for Internet Message Access Protocol,
  a method of accessing electronic mail or bulletin
  board messages that are kept on a (possibly
  shared) mail server. It permits a "client" email
  program to access remote message stores as if
  they were local. Email stored on an IMAP server
  can be manipulated from a desktop at home, a
  workstation at the office, and a notebook while
  traveling, without transferring messages or files
  back and forth between these.

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Common Mail Servers

• Generic POP/SMTP
• IMAIL Windows
• sendmail Unix, Linux, Penix
• Microsoft Exchange
• Lotus Domino / Notes
• IBM Office (proprietary)

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Web-based e-mail

• Provides an HTML page on a web server accessible
  from any browser to manage your e-mail.
  Examples
• IMAIL roicorporation.com/mail
  http//roicorporation.com8383
• hotmail.com
• mail.yahoo.com

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QUESTIONS

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