[cvsnt] Strange behaviour of cvs status on a VMWare server...

Peter Crowther Peter.Crowther at melandra.com
Mon Oct 30 09:43:10 GMT 2006

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> From: Bo Berglund
> PMTU is something I don't even have a clue as to what it is....

Path maximum transmission unit.  Different links along the route from
sender to recipient can set different MTUs - many old modem lins on PPP
used to have about a 600-byte MTU, for example.  Even if you were on
Ethernet at both ends with a 1500 byte MTU, if you sent a packet via a
modem between two offices and it was over 600 bytes it would get
fragmented (or dropped if it had its don't-fragment bit set).

> What can I do next (the Wireshark suggestion is tried but I don't
> really understand what to do with it)?

If we're narrowing this down to the network stack, as it seems... 

1) Check VMware Infrastructure for known bugs in its network stack.  A
long shot.

2) As I said before, talk to your network+firewall person/people (I
don't know who manages that on your network).

3) Run Wireshark on the server and client *at the same time*.  Capture
all traffic going to/from the other machine's IP address (i.e. on the
server, capture all traffic to/from the client).  Start both captures,
run the command that fails, stop and review both captures.  You're
looking for differences between them - on a reliable network, you should
see exactly the same packets at both ends.  A certain number of TCP
retransmissions may happen if the network's busy, but it shouldn't be
enough to kill the connection (you'll see the transmission of an
identical packet some time after the original was transmitted but not
received).  If you see any differences between the two traces, your
problem is almost certainly somewhere on the network.

4) If you can find out enough detail, tell us about the network
infrastructure between the virtual server and the two workstations on
which you're testing, and the firewalling on each workstation and the

5) Hire Saint Dogbert to shout "Out! you demons of stupidity!" at client
and server and see if it makes any difference, as by this time most
rational forms of investigation have failed ;-).

		- Peter

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