Proposed Changes to RCO-RJE Protocol for use on X25
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1. In the 'Yellow book' specification of the Transport layer there is no
   provision for a non-destructive disconnect.  Currently RJE protocol
   operates by transmitting the last packet of a file followed immediately
   by Send Block+disconnect (a non-destructive disconnect).

      Proposal a)  A marker, ie a record length of 16_FFFF will be send on
                   the end of every RJE connection.  When the receiver has
                   dealt with the file it will then clear down the connection
                   with a Transport Service (TS) Disconnect.

               b)  It will be necessary to distinguish between a 
                   TS Disconnect that means 'file lost' (current meaning)
                   and a 'normal' Disconnect.  The proposal is that the
                   qualifier on the TS Disconnect should be zero if the
                   file is received correctly, non-zero otherwise.


2. The RCO-RJE protocol uses a byte (USER FLAGS) which is actually part of
   the NSI header,  ITP does not use this byte leading to problems
   when converting level 3 protocols.

      Proposal c)  That the USER FLAGS byte is no longer used in RJE
                   data packets.

 Consequences: In most cases there should normally be no difference, but there
               are 3 cases where there definitely is:-

      1) Some line printer handlers behave differently when 'binary' is set
         on a file.

      Proposal d)  Line Printers should not need to look at the type of file.

      2) Paper Tape Punch: If a file is sent in 'Iso', parity and cr-before-lf
         are added.

      Proposal e)  That the normal Paper Tape Punch facility (6) is treated
                   as needing parity etc, a new facilty (23) is used for
                  Binary PPs.

      3) Binary set on the Card Reader Stream:

      Proposal f) That Binary Cards are sent on facility 13. (The normal 
                  definition of facility 13 is that no characters in the data
                  stream are added or removed).

3. As Send Messages will probably last for a longer period under X25 than
   the RJE protocol (because of FTP), it would seem reasonable to move
   towards tidying them up.

      Proposal g)  That text within Send Messages will consist of a single
                   record with a single byte length at the front. Both
                   CR and LF should be used in multi-line messages.



4.  In order to avoid changing all the existing software, the new-style
    RJE will only be supported on X25 networks and RJE traffic between
    NSI and X25 networks will have to be spooled through a mainframe.


                                                      Brian Gilmore
                                                       28.June.82