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From: wiltzius@lll-lcc.UUCP (Dave P. Wiltzius)
Newsgroups: comp.protocols.tcp-ip
Subject: TCP Retries
Message-ID: <2755@lll-lcc.UUCP>
Date: 13 Feb 90 04:27:29 GMT
Reply-To: wiltzius@lll-crg.UUCP (Dave P. Wiltzius)
Organization: CRG, Lawrence Livermore Labs
Lines: 22


I'm testing my port of a version of 4.3BSD TCP/IP code.  In
doing so, I discard in the loopback driver every Nth packet
(say, N=10).  This results in the MBUF pool being quickly
depleted.  I discovered that the TCP input routine will
save all out of order TCP packets waiting for the TCP retry
to fill in the gaps.  Hence most of the MBUF pool is
enqueued on this TCP fragment/reassembly list for this
TCPCB.  Also, the sender continues to get ACKs advertising
the largest window since the receive socket buffer is
empty.

Nothing particularly evil happens and since this is
a very degenerate case, perhaps I should just shrug
my shoulders and go on with life.  But it does bother
me a bit - rightfully so?  (Couldn't the window advertised
by the receiver close, or a limit made on the number
of out-of-order TCP packets on a TCPCB?)

Thanks for any help.
  Dave (wiltzius@lll-lcc.llnl.gov)