

Network Working Group                                          J. Postel
Request for Comments: 840                                            ISI
                                                              April 1983

                           Official Protocols


This RFC identifies the documents specifying the official protocols used
in the Internet.  Annotations identify any revisions or changes planned.

To first order, the official protocols are those in the Internet
Protocol Transition Workbook (IPTW) dated March 1982.  There are several
protocols in use that are not in the IPTW.  A few of the protocols in
the IPTW have been revised these are noted here.  In particular, the
mail protocols have been revised and issued as a volume titled "Internet
Mail Protocols" dated November 1982.  There is a volume of protocol
related information called the Internet Protocol Implementers Guide
(IPIG) dated August 1982.  A few of the protocols (in particular the
Telnet Options) have not been revised for many years, these are found in
the old ARPANET Protocol Handbook (APH) dated January 1978.

This document is organized as a sketchy outline.  The entries are
protocols (e.g., Transmission Control Protocol).  In each entry there
are notes on status, specification, comments, other references,
dependencies, and contact.

   The status is one of: required, recommended, elective, or
   experimental.

   The specification identifies the protocol defining documents.

   The comments describe any differences from the specification or
   problems with the protocol.

   The other references identify documents that comment on or expand on
   the protocol.

   The dependencies indicate what other protocols are called upon by
   this protocol.

   The contact indicates a person who can answer questions about the
   protocol.












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   In particular, the status may need some further clarification:

      required

         - all hosts must implement the required protocol,

      recommended

         - all hosts are encouraged to implement the recommended
         protocol,

      elective

         - hosts may implement or not the elective protocol,

      experimental

         - hosts should not implement the experimental protocol unless
         they are participating in the experiment and have coordinated
         their use of this protocol with the contact person, and

      none

         - this is not a protocol.

Overview

   Catenet Model

      STATUS:  None

      SPECIFICATION:  IEN 48 (in IPTW)

      COMMENTS:

         Gives an overview of the organization and principles of the
         Internet.

         Could be revised and expanded.

      OTHER REFERENCES:

      DEPENDENCIES:

      CONTACT: Postel@USC-ISIF






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Network Level

   Internet Protocol (IP)

      STATUS:  Required

      SPECIFICATION:  RFC 791 (in IPTW)

      COMMENTS:

         A few minor problems have been noted in this document.

         The most serious is a bit of confusion in the route options.
         The route options have a pointer that indicates which octet of
         the route is the next to be used.  The confusion is between the
         phrases "the pointer is relative to this option" and "the
         smallest legal value for the pointer is 4".  If you are
         confused, forget about the relative part, the pointer begins
         at 4.

         Another important point is the alternate reassembly procedure
         suggested in RFC 815.

         Note that ICMP is defined to be an integral part of IP.  You
         have not completed an implementation of IP if it does not
         include ICMP.

      OTHER REFERENCES:

         RFC 815 (in IPIG) - IP Datagram Reassembly Algorithms

         RFC 814 (in IPIG) - Names, Addresses, Ports, and Routes

         RFC 816 (in IPIG) - Fault Isolation and Recovery

         RFC 817 (in IPIG) - Modularity and Efficiency in Protocol
         Implementation

      DEPENDENCIES:

      CONTACT: Postel@USC-ISIF










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   Internet Control Message Protocol (ICMP)

      STATUS:  Required

      SPECIFICATION:  RFC 792 (in IPTW)

      COMMENTS:

         A few minor errors in the document have been noted.
         Suggestions have been made for additional types of redirect
         message and additional destination unreachable messages.

      OTHER REFERENCES:

      DEPENDENCIES: Internet Protocol

      CONTACT: Postel@USC-ISIF

Host Level

   User Datagram Protocol (UDP)

      STATUS:  Recommended

      SPECIFICATION:  RFC 768 (in IPTW)

      COMMENTS:

         The only change noted for the UDP specification is a minor
         clarification that if in computing the checksum a padding octet
         is used for the computation it is not transmitted or counted in
         the length.

      OTHER REFERENCES:

      DEPENDENCIES: Internet Protocol

      CONTACT: Postel@USC-ISIF













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   Transmission Control Protocol (TCP)

      STATUS:  Recommended

      SPECIFICATION:  RFC 793 (in IPTW)

      COMMENTS:

         Many comments and corrections have been received for the TCP
         specification document.  These are primarily document bugs
         rather than protocol bugs.

         Event Processing Section:  There are many minor corrections and
         clarifications needed in this section.

         Push:  There are still some phrases in the document that give a
         "record mark" flavor to the push.  These should be further
         clarified.  The push is not a record mark.

         Listening Servers:  Several comments have been received on
         difficulties with contacting listening servers.  There should
         be some discussion of implementation issues for servers, and
         some notes on alternative models of system and process
         organization for servers.

         Maximum Segment Size:  The maximum segment size option should
         be generalized and clarified.  It can be used to either
         increase or decrease the maximum segment size from the default.
         The default should be established more clearly.  The default is
         based on the default maximum Internet Datagram size which is
         576 octets counting the IP and TCP headers.  The option counts
         only the segment data.  For each of IP and TCP the minimum
         header is 20 octets and the maximum header is 60 octets. So the
         default maximum data segment is could be anywhere from 456 to
         536 octets.  The current proposal is to set it at 536 data
         octets.

         Idle Connections:  There have been questions about
         automatically closing idle connections.  Idle connections are
         ok, and should not be closed.  There are several cases where
         idle connections arise, for example, in Telnet when a user is
         thinking for a long time following a message from the server
         computer before his next input.  There is no TCP "probe"
         mechanism, and none is needed.

         Queued Receive Data on Closing:  There are several points where
         it is not clear from the description what to do about data
         received by the TCP but not yet passed to the user,
         particularly when the connection is being closed.  In general,


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         the data is to be kept to give to the user if he does a RECV
         call.

         Out of Order Segments:  The description says that segments that
         arrive out of order, that is, are not exactly the next segment
         to be processed, may be kept on hand.  It should also point out
         that there is a very large performance penalty for not doing
         so.

         User Time Out:  This is the time out started on an open or send
         call.  If this user time out occurs the user should be
         notified, but the connection should not be closed or the TCB
         deleted.  The user should explicitly ABORT the connection if he
         wants to give up.

      OTHER REFERENCES:

         RFC 813 (in IPIG) - Window and Acknowledgement Strategy in TCP

         RFC 814 (in IPIG) - Names, Addresses, Ports, and Routes

         RFC 816 (in IPIG) - Fault Isolation and Recovery

         RFC 817 (in IPIG) - Modularity and Efficiency in Protocol
         Implementation

      DEPENDENCIES: Internet Protocol

      CONTACT: Postel@USC-ISIF

   Host Monitoring Protocol (HMP)

      STATUS:  Elective

      SPECIFICATION:  IEN 197

      COMMENTS:

         This is a good tool for debuging protocol implementations in
         small remotely located computers.

         This protocol is used to monitor Internet gateways and the
         TACs.

      OTHER REFERENCES:

      DEPENDENCIES: Internet Protocol

      CONTACT: Hinden@BBN-UNIX


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   Cross Net Debugger (XNET)

      STATUS:  Elective

      SPECIFICATION:  IEN 158

      COMMENTS:

         This specification should be updated and reissued as an RFC.

      OTHER REFERENCES:

         RFC 643

      DEPENDENCIES: Internet Protocol

      CONTACT: Postel@USC-ISIF

   Exterior Gateway Protocol (EGP)

      STATUS:  Experimental

      SPECIFICATION:  RFC 827

      COMMENTS:

         Please discuss any plans for implementation or use of this
         protocol with the contact.

      OTHER REFERENCES:

      DEPENDENCIES: Internet Protocol

      CONTACT: Postel@USC-ISIF

















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   Gateway Gateway Protocol (GGP)

      STATUS:  Experimental

      SPECIFICATION:  RFC 823

      COMMENTS:

         Please discuss any plans for implementation or use of this
         protocol with the contact.

      OTHER REFERENCES:

      DEPENDENCIES: Internet Protocol

      CONTACT: Brescia@BBN-UNIX

   Multiplexing Protocol

      STATUS:  Experimental

      SPECIFICATION:  IEN 90

      COMMENTS:

         No current experiment in progress.  There is some question as
         to the extent to which the sharing this protocol envisions can
         actually take place.  Also, there are some issues about the
         information captured in the multiplexing header being (a)
         insufficient, or (b) over specific.

         Please discuss any plans for implementation or use of this
         protocol with the contact.

      OTHER REFERENCES:

      DEPENDENCIES: Internet Protocol

      CONTACT: Postel@USC-ISIF












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   Stream Protocol (ST)

      STATUS:  Experimental

      SPECIFICATION:  IEN 119

      COMMENTS:

         The implementation of this protocol has evolved and may no
         longer be consistent with this specification.  The document
         should be updated and issued as an RFC.

         Please discuss any plans for implementation or use of this
         protocol with the contact.

      OTHER REFERENCES:

      DEPENDENCIES: Internet Protocol

      CONTACT: Forgie@BBN

   Network Voice Protocol (NVP-II)

      STATUS:  Experimental

      SPECIFICATION:  RFC xxx

      COMMENTS:

         The specification is an ISI Internal Memo which should be
         updated and issued as an RFC.

         Please discuss any plans for implementation or use of this
         protocol with the contact.

      OTHER REFERENCES:

      DEPENDENCIES: Internet Protocol, Stream Protocol

      CONTACT: Casner@USC-ISIB











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Application Level

   Telnet Protocol (TELNET)

      STATUS:  Recommended

      SPECIFICATION:  RFC 764 (in IPTW)

      COMMENTS:

         A few minor typographical errors should be corrected and some
         clarification of the SYNCH mechanism should be made.

      OTHER REFERENCES:

      DEPENDENCIES: Transmission Control Protocol

      CONTACT: Postel@USC-ISIF

   Telnet Options (TELNET)

      Number   Name                                   RFC   NIC  APH USE
      ------   ------------------------------------   ---  ----- --- ---
         0     Binary Transmission                    ...  15389 yes yes
         1     Echo                                   ...  15390 yes yes
         2     Reconnection                           ...  15391 yes  no
         3     Suppress Go Ahead                      ...  15392 yes yes
         4     Approximate Message Size Negotiation   ...  15393 yes  no
         5     Status                                 651  31154 yes yes
         6     Timing Mark                            ...  16238 yes yes
         7     Remote Controlled Trans and Echo       726  39237 yes  no
         8     Output Line Width                      ...  20196 yes  no
         9     Output Page Size                       ...  20197 yes  no
        10     Output Carriage-Return Disposition     652  31155 yes  no
        11     Output Horizontal Tabstops             653  31156 yes  no
        12     Output Horizontal Tab Disposition      654  31157 yes  no
        13     Output Formfeed Disposition            655  31158 yes  no
        14     Output Vertical Tabstops               656  31159 yes  no
        15     Output Vertical Tab Disposition        657  31160 yes  no
        16     Output Linefeed Disposition            658  31161 yes  no
        17     Extended ASCII                         698  32964 yes  no
        18     Logout                                 727  40025 yes  no
        19     Byte Macro                             735  42083 yes  no
        20     Data Entry Terminal                    732  41762 yes  no
        21     SUPDUP                             734 736  42213 yes  no
        22     SUPDUP Output                          749  45449  no  no
        23     Send Location                          779  -----  no  no
       255     Extended-Options-List                  ...  16239 yes yes



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      STATUS:  Elective

      SPECIFICATION:  (in APH)

      COMMENTS:

         There is an open question about some of these.  Most of the
         options are implemented by so few hosts that perhaps they
         should be eliminated.  These should all be studied and the
         useful ones reissued as RFCs.

         The last column (USE) of the table above indicates which
         options are in general use.

         The following are recommended:  Binary Transmission, Echo,
         Suppress Go Ahead, Status, Timing Mark, and Extended Options
         List.

         Many of these must be revised for use with TCP.

      OTHER REFERENCES:

      DEPENDENCIES: Telnet

      CONTACT: Postel@USC-ISIF

   File Transfer Protocol (FTP)

      STATUS:  Recommended

      SPECIFICATION:  RFC 765 (in IPTW)

      COMMENTS:

         There are a number of minor corrections to be made.  A major
         change is the deletion of the mail commands, and a major
         clarification is needed in the discussion of the management of
         the data connection.  Also, a suggestion has been made to
         include some directory manipulation commands (RFC 775).

         Eventhough the MAIL features are defined in this document, they
         are not to be used.  The SMTP protocol is to be used for all
         mail service in the Internet.

         Data Connection Management:

            a.  Default Data Connection Ports:  All FTP implementations
            must support use of the default data connection ports, and
            only the User-PI may initiate the use of non-default ports.


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            b.  Negotiating Non-Default Data Ports:   The User-PI may
            specify a non-default user side data port with the PORT
            command.  The User-PI may request the server side to
            identify a non-default server side data port with the PASV
            command.  Since a connection is defined by the pair of
            addresses, either of these actions is enough to get a
            different data connection, still it is permitted to do both
            commands to use new ports on both ends of the data
            connection.

            c.  Reuse of the Data Connection:  When using the stream
            mode of data transfer the end of the file must be indicated
            by closing the connection.  This causes a problem if
            multiple files are to be transfered in the session, due to
            need for TCP to hold the connection record for a time out
            period to guarantee the reliable communication.  Thus the
            connection can not be reopened at once.

               There are two solutions to this problem.  The first is to
               negotiate a non-default port (as in (b) above).  The
               second is to use another transfer mode.

               A comment on transfer modes.  The stream transfer mode is
               inherently unreliable, since one can not determine if the
               connection closed prematurely or not.  The other transfer
               modes (Block, Compressed) do not close the connection to
               indicate the end of file.  They have enough FTP encoding
               that the data connection can be parsed to determine the
               end of the file.  Thus using these modes one can leave
               the data connection open for multiple file transfers.

               Why this was not a problem with the old NCP FTP:

                  The NCP was designed with only the ARPANET in mind.
                  The ARPANET provides very reliable service, and the
                  NCP counted on it.  If any packet of data from an NCP
                  connection were lost or damaged by the network the NCP
                  could not recover.  It is a tribute to the ARPANET
                  designers that the NCP FTP worked so well.

                  The TCP is designed to provide reliable connections
                  over many different types of networks and
                  interconnections of networks.  TCP must cope with a
                  set of networks that can not promise to work as well
                  as the ARPANET.  TCP must make its own provisions for
                  end-to-end recovery from lost or damaged packets.
                  This leads to the need for the connection phase-down
                  time-out.  The NCP never had to deal with
                  acknowledgements or retransmissions or many other


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                  things the TCP must do to make connection reliable in
                  a more complex world.

         LIST and NLST:

            There is some confusion about the LIST an NLST commands, and
            what is appropriate to return.  Some clarification and
            motivation for these commands should be added to the
            specification.

      OTHER REFERENCES:

         RFC 678 - Document File Format Standards

      DEPENDENCIES: Transmission Control Protocol

      CONTACT: Postel@USC-ISIF

   Trivial File Transfer Protocol (TFTP)

      STATUS:  Elective

      SPECIFICATION:  RFC 783 (in IPTW)

      COMMENTS:

         No known problems with this specification.  This is in use in
         several local networks.

      OTHER REFERENCES:

      DEPENDENCIES: User Datagram Protocol

      CONTACT: Postel@USC-ISIF

   Simple Mail Transfer Protocol (SMTP)

      STATUS:  Recommended

      SPECIFICATION:  RFC 821

      COMMENTS:

         This has been revised since the IPTW, it is in the "Internet
         Mail Protocols" volume of November 1982.  RFC 788 (in IPTW) is
         obsolete.

         There have been many misunderstandings and errors in the early



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         implementations.  Some documentation of these problems can be
         found in the file [ISIF]<SMTP>MAIL.ERRORS.

         Some minor differences between RFC 821 and RFC 822 should be
         resolved.

      OTHER REFERENCES:

         RFC 822 - Mail Header Format Standards

            This has been revised since the IPTW, it is in the "Internet
            Mail Protocols" volume of November 1982.  RFC 733 (in IPTW)
            is obsolete.  Further revision of RFC 822 is needed to
            correct some minor errors in the details of the
            specification.

      DEPENDENCIES: Transmission Control Protocol

      CONTACT: Postel@USC-ISIF

   Remote Job Entry (RJE)

      STATUS:  Elective

      SPECIFICATION:  RFC 407 (in APH)

      COMMENTS:

         Some changes needed for use with TCP.

         No known active implementations.

      OTHER REFERENCES:

      DEPENDENCIES: File Transfer Protocol
                    Transmission Control Protocol

      CONTACT: Postel@USC-ISIF













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   Remote Job Service (NETRJS)

      STATUS:  Elective

      SPECIFICATION:  RFC 740 (in APH)

      COMMENTS:

         Used with the UCLA IBM OS system.

         Please discuss any plans for implementation or use of this
         protocol with the contact.

         Revision in progress.

      OTHER REFERENCES:

      DEPENDENCIES: Transmission Control Protocol

      CONTACT: Braden@USC-ISIA

   Remote Telnet Service

      STATUS:  Elective

      SPECIFICATION:  RFC 818

      COMMENTS:

      OTHER REFERENCES:

      DEPENDENCIES: Telnet, Transmission Control Protocol

      CONTACT: Postel@USC-ISIF

   Graphics Protocol

      STATUS:  Elective

      SPECIFICATION:  NIC 24308 (in APH)

      COMMENTS:

         Very minor changes needed for use with TCP.

         No known active implementations.

      OTHER REFERENCES:



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      DEPENDENCIES: Telnet, Transmission Control Protocol

      CONTACT: Postel@USC-ISIF

   Echo Protocol

      STATUS:  Recommended

      SPECIFICATION:  RFC 347

      COMMENTS:

         This specification should be revised for use with TCP and
         reissued.

      OTHER REFERENCES:

      DEPENDENCIES: Transmission Control Protocol
                    or User Datagram Protocol

      CONTACT: Postel@USC-ISIF

   Discard Protocol

      STATUS:  Elective

      SPECIFICATION:  RFC 348

      COMMENTS:

         This specification should be revised for use with TCP and
         reissued.

      OTHER REFERENCES:

      DEPENDENCIES: Transmission Control Protocol
                    or User Datagram Protocol

      CONTACT: Postel@USC-ISIF












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   Character Generator Protocol

      STATUS:  Elective

      SPECIFICATION:  RFC 429

      COMMENTS:

         This specification should be revised for use with TCP and
         reissued.

      OTHER REFERENCES:

      DEPENDENCIES: Transmission Control Protocol
                    or User Datagram Protocol

      CONTACT: Postel@USC-ISIF

   Quote of the Day Protocol

      STATUS:  Elective

      SPECIFICATION:  RFC xxx

      COMMENTS:

         Open a connection to this server, it sends you a quote (as a
         character string), and closes the connection.  This should be
         described in an RFC.

      OTHER REFERENCES:

      DEPENDENCIES: Transmission Control Protocol
                    or User Datagram Protocol

      CONTACT: Postel@USC-ISIF

   Active Users Protocol

      STATUS:  Elective

      SPECIFICATION:  RFC xxx

      COMMENTS:

         Open a connection to this server, it sends you a list of the
         currently logged in users (as a character string), and closes
         the connection.  This should be described in an RFC.



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      OTHER REFERENCES:

      DEPENDENCIES: Transmission Control Protocol
                    or User Datagram Protocol

      CONTACT: Postel@USC-ISIF

   Finger Protocol

      STATUS:  Elective

      SPECIFICATION:  RFC 742 (in APH)

      COMMENTS:

         Some extensions have been suggested.

         Some changes are are needed for TCP.

      OTHER REFERENCES:

      DEPENDENCIES: Transmission Control Protocol

      CONTACT: Postel@USC-ISIF

   NICNAME Protocol

      STATUS:  Elective

      SPECIFICATION:  RFC 812 (in IPTW)

      COMMENTS:

         Accesses the ARPANET Directory database.

      OTHER REFERENCES:

      DEPENDENCIES: Transmission Control Protocol

      CONTACT: Feinler@SRI-NIC











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   HOSTNAME Protocol

      STATUS:  Elective

      SPECIFICATION:  RFC 811 (in IPTW)

      COMMENTS:

         Accesses the Registered Internet Hosts database (HOSTS.TXT).

      OTHER REFERENCES:

         RFC 810 - Host Table Specification

      DEPENDENCIES: Transmission Control Protocol

      CONTACT: Feinler@SRI-NIC

   Host Name Server Protocol

      STATUS:  Experimental

      SPECIFICATION:  IEN 116 (in IPTW)

      COMMENTS:

         This specification has significant problems:  1) The name
         syntax is out of date.  2) The protocol details are ambiguous,
         in particular, the length octet either does or doesn't include
         itself and the op code.  3) The extensions are not supported by
         any known implementation.

         Work is in progress on a significant revision.  Further
         implementations of this protocol are not advised.

         Please discuss any plans for implementation or use of this
         protocol with the contact.

      OTHER REFERENCES:

      DEPENDENCIES: User Datagram Protocol

      CONTACT: Postel@USC-ISIF








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   CSNET Mailbox Name Server Protocol

      STATUS:  Experimental

      SPECIFICATION:  CS-DN-2

      COMMENTS:

         Please discuss any plans for implementation or use of this
         protocol with the contact.

      OTHER REFERENCES:

      DEPENDENCIES: Transmission Control Protocol

      CONTACT: Solomon@UWISC

   Daytime Protocol

      STATUS:  Elective

      SPECIFICATION:  RFC xxx

      COMMENTS:

         Open a connection to this server, it sends you the date and
         time (as a character string), and closes the connection.  This
         should be described in an RFC.

      OTHER REFERENCES:

      DEPENDENCIES: Transmission Control Protocol
                    or User Datagram Protocol

      CONTACT: Postel@USC-ISIF

   Time Server Protocol

      STATUS:  Recommended

      SPECIFICATION:  IEN 142

      COMMENTS:

         Open a connection to this server, it sends you the date and
         time (as a 32-bit number), and closes the connection.  Or send
         a user datagram and it send back a datagram containing the date
         and time (as a 32-bit number).



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         No known problems.  Specification should be reissued as an RFC.

      OTHER REFERENCES:

      DEPENDENCIES: Transmission Control Protocol
                    or User Datagram Protocol

      CONTACT: Postel@USC-ISIF

   DCNET Time Server Protocol (Internet Clock Service)

      STATUS:  Elective

      SPECIFICATION:  RFC 778

      COMMENTS:

      OTHER REFERENCES:

      DEPENDENCIES: Internet Control Message Protocol

      CONTACT: Mills@LINKABIT-DCN6

   SUPDUP Protocol

      STATUS:  Elective

      SPECIFICATION:  RFC 734 (in APH)

      COMMENTS:

      OTHER REFERENCES:

      DEPENDENCIES: Transmission Control Protocol

      CONTACT: Admin.MRC@SU-SCORE

   Internet Message Protocol (MPM)

      STATUS:  Experimental

      SPECIFICATION:  RFC 753

      COMMENTS:

         This is an experimental multimedia mail transfer protocol.  The
         implementation is called a Message Processing Module or MPM.




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         Please discuss any plans for implementation or use of this
         protocol with the contact.

      OTHER REFERENCES:

         RFC 767 - Structured Document Formats

      DEPENDENCIES: Transmission Control Protocol

      CONTACT: Postel@USC-ISIF

Appendices

   Assigned Numbers

      STATUS:  None

      SPECIFICATION:  RFC 820

      COMMENTS:

         Describes the fields of various protocols that are assigned
         specific values for actual use, and lists the currently
         assigned values.

         Issued January 1983, replaces RFC 790 in IPTW.

      OTHER REFERENCES:

      CONTACT: Postel@USC-ISIF

   Pre-emption

      STATUS:  Elective

      SPECIFICATION:  RFC 794 (in IPTW)

      COMMENTS:

         Describes how to do pre-emption of TCP connections.

      OTHER REFERENCES:

      CONTACT: Postel@USC-ISIF







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   Service Mappings

      STATUS:  None

      SPECIFICATION:  RFC 795 (in IPTW)

      COMMENTS:

         Describes the mapping of the IP type of service field onto the
         parameters of some specific networks.

         Out of date, needs revision.

      OTHER REFERENCES:

      CONTACT: Postel@USC-ISIF

   Address Mappings

      STATUS:  None

      SPECIFICATION:  RFC 796 (in IPTW)

      COMMENTS:

         Describes the mapping of the IP address field onto the address
         field of some specific networks.

         Out of date, needs revision.

      OTHER REFERENCES:

      CONTACT: Postel@USC-ISIF


















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