Binkp protocol extension Non-reliable Mode

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FTSC                             FIDONET TECHNICAL STANDARDS COMMITTEE
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Publication:    FTS-1028
Revision:       1
Title:          Binkp protocol extension Non-reliable Mode
Authors:        Michiel Broek
Issue Date:     1 December 2005
Review Date:    1 December 2007
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Contents:
         1. Definitions
         2. Binkp Non-reliable Mode
         3. Implementation
         A. References
         B. History
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Status of this document
-----------------------

   This document is a Fidonet Technical Standard (FTS).

   This document specifies an optional Fidonet standard protocol for
   the Fidonet community.

   This document is released to the public domain, and may be used,
   copied or modified for any purpose whatever.


1. Definitions
--------------

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
   NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL"
   in this document are to be interpreted as described in [FTA-1006].


2. Binkp Non-reliable Mode
--------------------------

   Non-reliable mode solves the problem with frequently aborted
   connections when the sides can not successfully complete file
   transfer before connection is broken. In this case, if the
   transmitting side starts retransmission from offset 0, performance
   degrades as by the time it receives M_GET from the remote, network
   buffers are already full and by the time they are freed for
   retransmission from requested offset, the connection might go down
   again.

   In order to circumvent this problem, a mailer can request the
   remote to enter non-reliable mode. If the remote supports this mode
   it MUST switch non-reliable mode on. If the remote doesn't support
   this mode or non-reliable mode is disabled on remote, it will
   continue to use ordinary binkp file send mode.

   Non-reliable mode short notation is "NR mode".

   A mailer MAY request the remote to send files in NR mode by sending
   a M_NUL "OPT NR" frame at any time during the session. The remote
   MAY reply by sending an M_NUL "OPT NR" frame. If remote sends the
   M_NUL "OPT NR" frame, a mailer MUST send files in NR mode if it
   supports this.

   When session is in non-reliable mode, the transmitting side MAY
   send -1 for the offset value in M_FILE command. If it does so, it
   SHOULD wait for the M_GET frame from the receiving side that
   explicitly specifies file offset and start transmitting file data
   from this offset. If the receiving side has indicated that it
   supports non-reliable mode by sending M_NUL "OPT NR" frame, it MUST
   recognize -1 as the file offset in M_FILE command as an explicit
   request for the file offset and transmit an appropriate M_GET frame
   as soon as possible.

   It should be understood that this option degrades performance over
   regular quality connections and it should be used only if
   absolutely necessary.


3. Implementation
-----------------

   The implementation of NR mode is optional for binkp/1.0 mailers.
   In binkp/1.1 mailers NR mode MUST be implemented, see FSP-1024.


A. References
-------------

   [FSP-1018]
           Binkp/1.0 Protocol specification.

   [FSP-1024]
           Binkp/1.1 Protocol specification.

   [FTA-1006]
           Key words to indicate requirement levels, Fidonet Technical
           Standards Committee administrative. FTA-1006.


B. History
----------

   Rev.1, 20051201: Initial Release.