Proper Response to an ABTS issued because of a lost command

[Zeitler, Carl]

* From the T10 Reflector (t10 at t10.org), posted by:
* "Zeitler, Carl" <Carl.Zeitler at compaq.com>
*
This note is in response to Action Item # 9 from the last Joint T11.3/T10
meeting on April 5-
"On a lost command check to see if the LS bit needs to be set to abort the
Exchange".  

The short answer is NO.  The rationale follows.

The situation arises in Class 2 when the command is lost and ABTS (sequence)
is issued.

>From FC_FS:

23.6.1.1 Abort Sequence Protocol

Special case - new Exchange, P. 357 hard copy

		
If a Sequence Initiator of the ABTS frame attempts to originate a new
Exchange and a Sequence timeout occurs, the Sequence Initiator shall
transmit the ABTS frame as in the ABTS protocol defined.  If the Sequence
Recipient receives an ABTS frame for an Exchange which is unknown, it shall
Open and Exchange Status Block, with OX_ID = value of the ABTS, RX_ID= hex
'ffff', and post the SEQ_ID of the ABTS frame.  The Basic Accept Payload
shall indicate invalid SEQ_ID, a low SEQ_CNT set to zero, and a high SEQ_CNT
set to the SEQ_CNT of the ABTS frame.


15.2.2.1 Aborting Sequences using ABTS, p. 161 hard copy

Reply Sequence

Basic Accept

3) To indicate that it has no information on the last deliverable Sequence,
and One or more Sequences are aborted at its end, the Sequence Recipient
shall set , in the BA_ACC payload, independent of Continuously Increasing
SEQ_CNT use

     SEQ_ID Validity = invalid (hex "00" )
     SEQ_ID = invalid in this case
     Low SEQ_CNT = hex '0000'
     High SEQ_CNT = SEQ_CNT of the ABTS frame.

15.2.2.2	Aborting an Exchange using ABTS.  P 163 hard copy

Reply Sequence

Basic Accept

2)To indicate it has no information on the last deliverable Sequence, an it
is aborting the entire Exchange,  The ABTS Recipient shall set the Last
Sequence F_CTL bit to 1 and shall set, in the BA_ACC payload,

     SEQ_ID Validity = invalid (hex '00')
     SEQ_ID = invalid in this case
     Low SEQ_CNT = hex '0000' and
     High SEQ_CNT = hex 'FFFF'


Since the specified payload of BA_ACC for aborting the Sequence matches the
requirements of the special case, and the BA_ACC payload for aborting the
Exchange does not match, my conclusion is that the Last Sequence F_CTL bit
(LS bit) is not set.

          


Regards, Carl

Carl Zeitler
Compaq Computer Corporation
MS 150801, 20555 SH249, Houston, TX 77070
Phone:281-518-5258 Fax: 281-514-5270
E-Mail: Carl.Zeitler at compaq.com

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