silent dropping of TCP segment

"Barry Reinhold" <[email protected]>
Newsgroups gmane.ietf.rddp
Message-ID <001401c41285$4b289e40$467fa8c0@i8600>
MPA clause 9, error semantics, states that an MPA aware TCP
implementation may silently drop a TCP segment when MPA detects a CRC
error. The goal of this TCP segment dropping would be to avoid forcing
the teardown of the stream by having TCP retransmit the segment.

However, clause 5.1.2 on page 11 requires that 

"The TCP layer MUST have committed to keeping each segment before it can
be passed to the MPA." 

I assume "committed" means that TCP ACKs the segment. Thus the segment
is ACKed before it is delivered to MPA. If this is the proper
understanding I don't see how "MPA" can silently drop a segment, since
by the time it can detect a CRC error TCP has already committed to it.

It is not clear to me why there is a "MUST" in clause 5.1.2. It would
seem desirable to allow MPA some control over when the ACK is to be
generated.

I would like to see the "MUST" removed from clause 5.1.2. 

Barry Reinhold
Lamprey Networks
[email protected]
(603) 868-8411
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