Subject: Defer-Receive State

From: [email-masked]
Date: Thu, 10 Mar 94 11:54:18 +0100

There are some state transitions concerning the Defer-Receive State (9)
which, to us, seem to be wrong:

A local TP in Send state (3) issuing a CMPTR call with prepare_to_receive_type 
set to CM_PREP_TO_RECEIVE_SYNC_LEVEL and sync_level = CM_SYNC_POINT changes
it's state to Defer-Receive (9) but still has send control, see the usage 
notes for CMPTR.

Due to these usage notes and the state table in appendix C, the local TP 
transfers the send control to the remote TP and enters Receive state (4)
when it issues a CMFLUS or CMCFM call.

1) This behaviour of CMFLUS and CMCFM differs from the behaviour of those
   calls when issued in the "normal" Send state, where send control is not
   transferred to the partner TP (except for the CMCFMD). To us there is 
   no reason for this difference.

2) Does the remote TP receive a status_received = CM_SEND_RECEIVED as a 
   result of the CMFLUS ?

3) Most important objection to this behaviour: 
   in OSI-TP there is no state change when the local application sends the 
   TP-DEFERRED-GRANT-CONTROL-req (which corresponds to the CMPTR). Thus
   the application remains in Send state and also does not transfer
   send control to the partner application when it sends a TP-HANDSHAKE-req
   (which corresponds to the CMCFM), except perhaps to receive the confirm.
   Running CPI-C on an OSI-TP CRM, this results in an inconsistency between
   the CPI-C state and the corresponding OSI-TP state.

To avoid these inconveniences we suggest to change the CPI-C state table in
such a way, that send control will NOT be transferred to the partner if 
CMFLUS or CMCFM are issued in Defer-Receive state, or, perhaps still better,
to skip that state totally and rather remember the fact that a CMPTR with
CM_PREP_TO_RECEIVE_SYNC_LEVEL was sent in a new characteristic.

An other point: did you receive our mail from the 3rd of March concerning the
problems of using CPI-C together with TX ? We did not receive any comments on
that yet.

    Best regards
      Uwe 

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Uwe Goellner                         |   Tel.:  07531-87-4628
Computer Gesellschaft Konstanz mbH   |   Fax:   07531-87-4888
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