From: peter@cujo.curtin.edu.au (Peter N Lewis)
Subject: PCRoute <-> Sun SPARC Slip-4.1 problems
Organization: Curtin University of Technology
Date: Sun, 11 Oct 1992 08:36:34 GMT

Hi All,

I've got PCRoute on an 8MHz IBM PC Clone connected via a 9600 baud
permanent modem link to a SPARC2 running slip-4.1.  It works fine for
the most part, but on large TCP sends from the SPARC to PCRoute, the
connection dies (eg, ftp put, or Sendmail transfers from the Sun to
machines connected via ethernet to the PCRoute box work fine if they are
short, but if they are larg (>30k) the connection aborts part way thru).
Connections in the other direction have no problems.

I don't really even know where to start looking.  It would seem likely
that the fault is on the Sun end, since I have PCRoute running at
another location (to a terminal server) without the problem.  It may be
to do with a lack of handshaking, since I'm not certain what the
handshaking setup on the sun, modems, or pcroute box is (the modems are
syncronous with sync<->async addapters at each end, just to confuse the
issue).

netstat -s says:
ip:
        166003 total packets received
        0 bad header checksums
        0 with size smaller than minimum
        0 with data size < data length
        0 with header length < data size
        0 with data length < header length
        255 fragments received
        0 fragments dropped (dup or out of space)
        0 fragments dropped after timeout
        71435 packets forwarded
        0 packets not forwardable
        0 redirects sent
        0 ip input queue drops
icmp:
        4 calls to icmp_error
        0 errors not generated 'cuz old message too short
        0 errors not generated 'cuz old message was icmp
        Output histogram:
                destination unreachable: 4
        0 messages with bad code fields
        0 messages < minimum length
        0 bad checksums
        0 messages with bad length
        Input histogram:
                destination unreachable: 2
                source quench: 2
        0 message responses generated
tcp:
        60804 packets sent
                45803 data packets (2902623 bytes)
                1363 data packets (683114 bytes) retransmitted
                12116 ack-only packets (10569 delayed)
                0 URG only packets
                4 window probe packets
                603 window update packets
                915 control packets
        91424 packets received
                45181 acks (for 2857596 bytes)
                1260 duplicate acks
                0 acks for unsent data
                45002 packets (3448495 bytes) received in-sequence
                492 completely duplicate packets (111043 bytes)
                48 packets with some dup. data (11473 bytes duped)
                1846 out-of-order packets (738127 bytes)
                0 packets (0 bytes) of data after window
                0 window probes
                589 window update packets
                5 packets received after close
                0 discarded for bad checksums
                0 discarded for bad header offset fields
                0 discarded because packet too short
        239 connection requests
        396 connection accepts
        632 connections established (including accepts)
        680 connections closed (including 37 drops)
        3 embryonic connections dropped
        43539 segments updated rtt (of 44407 attempts)
        814 retransmit timeouts
                31 connections dropped by rexmit timeout
        6 persist timeouts
        1 keepalive timeout
                1 keepalive probe sent
                0 connections dropped by keepalive
udp:
        0 incomplete headers
        0 bad data length fields
        0 bad checksums
        0 socket overflows

A diff before and after a failed ftp put from the sun shows:

[Most zero entries not shown]
ip:
        721 total packets received
        13 packets forwarded
tcp:
        510 packets sent
                385 data packets (78038 bytes)
                62 data packets (56398 bytes) retransmitted
                49 ack-only packets (30 delayed)
                14 control packets
        697 packets received
                365 acks (for 75155 bytes)
                40 duplicate acks
                0 acks for unsent data
                277 packets (568 bytes) received in-sequence
                0 completely duplicate packets (0 bytes)
                0 packets with some dup. data (0 bytes duped)
                5 out-of-order packets (0 bytes)
                0 packets (0 bytes) of data after window
                0 window probes
                7 window update packets
                1 packets received after close
                0 discarded for bad checksums
                0 discarded for bad header offset fields
                0 discarded because packet too short
        4 connection requests
        7 connection accepts
        11 connections established (including accepts)
        12 connections closed (including 1 drops)
        0 embryonic connections dropped
        323 segments updated rtt (of 341 attempts)
        19 retransmit timeouts
                1 connections dropped by rexmit timeout
        0 persist timeouts
        0 keepalive timeout
                0 keepalive probe sent
                0 connections dropped by keepalive

So, anyone got any ideas?  THANKS for any info!
   Peter.

Newsgroups: comp.protocols.tcp-ip.ibmpc,comp.sys.ibm.pc.hardware