RE: [ethmac] Lost Ethernet Data

["Kevin Kay" <Kevin.Kay@espipd.com>]

>From the SA and DA reversal on the two packets, I assume that your test
setup involves pinging a remote test unit and catching the echo reply.
So it seems that there are multiple potential failure points that have
to be eliminated.

Using a sniffer in your data path (via a hub and a Windows PC or laptop
with Ethereal - a free sniffer), you can monitor traffic between your
two devices.  You can also set up a capture filter to determine where
the first bad packet shows up (e.g., is your ping responder receiving
bogus data which means your transmit side is messed up, is your ping
responder getting good data but sending bad which means your test
equipment is messed up, or is the ping responder getting good data and
sending good data which means your receive side is messed up).  Note
that in this suggested sniffer setup you MUST use a hub because the
sniffer will not see the traffic if you use a switch.

I'm assuming here that the data below was captured from the host side
somehow after the full round trip (two passes through your MAC) had been
completed.  If so, you need to break the round trip up into individual
hops (via the sniffer) in order to figure out which hop is causing you
the problem.  Then you will know where to fight.

Regards,
Kevin


-----Original Message-----
From: Kyle Nesbit [mailto:kjnesbit@wisc.edu]
Sent: Thursday, December 05, 2002 9:50 AM
To: ethmac@opencores.org
Subject: [ethmac] Lost Ethernet Data


I am experiencing a strange problem with Igor's core that I wonder if
anyone
has seen before.  On a small fraction of the packets received there
seems to
be 32 bits missing and its always at the same location.  I have copied
an
example ping packet below.  You can see that at the 64th byte there
should
be 16 17 18 19, but this data is gone and the other data is shifted left
and
garbage is appended.  I am very confident that this is not a software
error
and since I am new at this, I am hoping that I am doing something stupid
that somebody can easily point out.


Incoming ping:

0000  12 34 56 78 9a bc 00 03 93 db cd dc 08 00 45 00   .4Vx..........E.
0010  00 54 5f c0 00 00 40 01 4a 06 12 34 56 03 12 34   .T_...@.J..4V..4
0020  56 78 08 00 32 0c 02 94 00 01 3d ee cd 15 00 0c   Vx..2.....=.....
0030  cd 4b 08 09 0a 0b 0c 0d 0e 0f 10 11 12 13 14 15   .K..............
0040  16 17 18 19 1a 1b 1c 1d 1e 1f 20 21 22 23 24 25   .......... !"#$%
0050  26 27 28 29 2a 2b 2c 2d 2e 2f 30 31 32 33 34 35   &'()*+,-./012345
0060  36 37                                             67


Outgoing ping:

0000  00 03 93 db cd dc 12 34 56 78 9a bc 08 00 45 00   .......4Vx....E.
0010  00 54 5f c0 00 00 40 01 52 07 12 34 56 78 12 34   .T_...@.R..4Vx.4
0020  56 03 00 00 32 0c 02 94 00 01 3d ee cd 15 00 0c   V...2.....=.....
0030  cd 4b 08 09 0a 0b 0c 0d 0e 0f 10 11 12 13 14 15   .K..............
0040  1a 1b 1c 1d 1e 1f 20 21 22 23 24 25 26 27 28 29   ...... !"#$%&'()
0050  2a 2b 2c 2d 2e 2f 30 31 32 33 34 35 36 37 6a ca   *+,-./01234567j.
0060  a8 93 91 2c a3 15                                 ...,..

Thank you,
Kyle Nesbit

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