No subject

Fri Jun 17 13:25:21 PDT 1994

This comment deals with recent suggestions (K. Chen, J. Coomes) to
eliminate an FCP  target's responsibility to terminate ambiguous
exchanges after an Abort Task Set, Clear task set,
and various forms of logout.

I do not think this requirement should be eliminated.
There are many reasons FCP requires ambiguous exchanges to be aborted,
but one of them is in the following case:

1. The initiator has given sequence initiative to the target and the
target has been sending data frames to the initiator and some of the
frames are unacknowledged.
2. The Initiator sends a Clear Task Set.
3. If the target does not abort the exchange, then the initiator may
assume that it can reuse the exchange and sequence ID in a new
4. Later, the frames from the ambiguous sequence may reappear and
cause a data integrity problem.

For this case and other reasons, I do not believe that FCP should be
changed. Targets must continue to be required to terminate exchanges
in ambiguous states.

                                 Giles Frazier
                                 IBM Austin
                                 gfrazier at

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