Thanks Martin
I realise that sniffing traffic on the wire is more practical, but I am in a
test environment in this case.
Wouldn't the machine on the mirrored port simply experience the same
problem?
(Oh wait, I see what you mean.. I am monitoring on the server... and the
large packets are out-going, and so therefore if I was sniffing on the wire
they would be of normal size.)
However, I understand this is an open source project, and I really want to
help (I beleive many other users have experienced this problem with perhaps
no resolution as to what is really going on).
But I'm not about to delve in the ins and outs or even the code of WinPCap.
For a novice user it would be helpful if either a) Large packets at least
had a mention, or b) The issue was at least mentioned in
http://wiki.wireshark.org/TCP_ACKed_lost_segment
Thanks for explaining Martin.
I will post some net caps perhaps on monday back in the office.
I opened the NetMon capture file in Wireshark and the large packets are
listed and the "acked lost segments" are no longer there.
However I still saw some "acked lost segment", god knows where they are
comming from. (I think we have a few problems with this applications use of
SOAP, which is what led me here in the first place!!)
Cheers!
Michael.
----- Original Message -----
From: "Martin Visser" <martinvisser99@xxxxxxxxx>
To: "Community support list for Wireshark" <wireshark-users@xxxxxxxxxxxxx>
Sent: Friday, January 07, 2011 3:14 PM
Subject: Re: [Wireshark-users] Packets not captured, tcp acking lost
segments. Large packets
Michael,
Normally your server will be connected to a switch. If this is a
manageable switch, you should be able to configure it to port-mirror,
which means a copy of the traffic on one port is sent to another port.
This will enable easy monitoring of your traffic, and you will see
what is actually going on the wire. When I meant "avoid", it is more
about making sure you see what is on the wire rather than the tricks
that the driver might be doing. (I try to avoid installing Wireshark
or Net Mon on production servers - not that it doesn't work, but I
don't want my measuring application potentially affecting the normal
performance of the server).
I'm not sure if there is possibly an issue with WinPcap library not
working properly on your box of not. You might want to post a small
capture file showing what you saw with Wireshark and what you captured
with Net Mon. (Also note that Wireshark can read Net Mon files - does
this show the difference as well?)
Regards, Martin
MartinVisser99@xxxxxxxxx
On 7 January 2011 14:27, Michael Lynch <michaellynch511@xxxxxxxxx> wrote:
Thanks Martin
I read up on LSO. It explains how these >4K packets are appearing
Yes I am running Wireshark on the application server. I had a hard time
installing it on my switch!! No CD-rom drive!! :)
(I am not sure what you mean by 'Server Switch')
But why is MS Net Mon seeing these large packets?
Wireshark is providing misleading information and I don't think i'm the
only
one that is suffering major confusion.
I think my self lucky as I have witnessed the packets in NetMon.
Most users on the net seem to have presumed that packets are being lost!
Wireshark will see the large segments go out.
But its not...?
You might want to capture on your server switch rather than the server
to avoid seeing this.
I don't want to avoid packets, I want to see the packets!
Cheers
Michael.
----- Original Message ----- From: "Martin Visser"
<martinvisser99@xxxxxxxxx>
To: "Community support list for Wireshark"
<wireshark-users@xxxxxxxxxxxxx>
Sent: Friday, January 07, 2011 1:46 PM
Subject: Re: [Wireshark-users] Packets not captured, tcp acking lost
segments. Large packets
It sounds like you are capturing traffic on the server rather than the
wire. If your server NIC and driver does Large Segment Offload, the
segmentation is done by the NIC, which allows the transfer from your
kernel to the NIC do be done in larger chunks, meaning a more
efficient transfer. Wireshark will see the large segments go out.
You might want to capture on your server switch rather than the server
to avoid seeing this.
Regards, Martin
MartinVisser99@xxxxxxxxx
On 7 January 2011 11:25, Michael Lynch <michaellynch511@xxxxxxxxx>
wrote:
Hi All
I think I've found something everyone may be interested in...
In wireshark I am monitoring traffic of a SOAP application.
Upon transfer of a BLOB, wire shark is showing many "Tcp ACKed lost
segment"
packets.
On top of this there is no evidence of any of the SOAP data, other than
the
initial header.
Now I've search for this lost segment business, and no forums really
seem
to
have much of a solution other than perhaps disabling sequence analysis.
However I think I have found the problem, but I have no understanding
of
the
whats and whys.
In Microsoft Net Mon, the data packets ARE THERE!!!
i.e
Sent packet: Captured Frame Length = 4434, Media Type = Ethernet...
Continuaion to packet #76.
Received packet: Ack
The received packet is the only packet that shows up in Wireshark! (I
have
cross referenced the Packet ID)
Wireshark is NOT COLLECTING LARGE PACKETS!!
I have no idea how packets THAT LARGE got onto the wire IN THE FIRST
PLACE!!
What is going on??!! :)
Cheers
Michael
___________________________________________________________________________
Sent via: Wireshark-users mailing list <wireshark-users@xxxxxxxxxxxxx>
Archives: http://www.wireshark.org/lists/wireshark-users
Unsubscribe: https://wireshark.org/mailman/options/wireshark-users
mailto:wireshark-users-request@xxxxxxxxxxxxx?subject=unsubscribe
___________________________________________________________________________
Sent via: Wireshark-users mailing list <wireshark-users@xxxxxxxxxxxxx>
Archives: http://www.wireshark.org/lists/wireshark-users
Unsubscribe: https://wireshark.org/mailman/options/wireshark-users
mailto:wireshark-users-request@xxxxxxxxxxxxx?subject=unsubscribe
___________________________________________________________________________
Sent via: Wireshark-users mailing list <wireshark-users@xxxxxxxxxxxxx>
Archives: http://www.wireshark.org/lists/wireshark-users
Unsubscribe: https://wireshark.org/mailman/options/wireshark-users
mailto:wireshark-users-request@xxxxxxxxxxxxx?subject=unsubscribe
___________________________________________________________________________
Sent via: Wireshark-users mailing list <wireshark-users@xxxxxxxxxxxxx>
Archives: http://www.wireshark.org/lists/wireshark-users
Unsubscribe: https://wireshark.org/mailman/options/wireshark-users
mailto:wireshark-users-request@xxxxxxxxxxxxx?subject=unsubscribe
