rfc840.txt

RFC 相关的技术文档

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.