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Wireshark-bugs: [Wireshark-bugs] [Bug 10125] New: TCP ACK timestamps are earlier in time than th

Date: Wed, 21 May 2014 14:34:48 +0000
Bug ID 10125
Summary TCP ACK timestamps are earlier in time than the corresponding TCP data frame for frames with a length > MTU
Classification Unclassified
Product Wireshark
Version 1.10.7
Hardware x86-64
OS Windows 7
Status UNCONFIRMED
Severity Major
Priority Low
Component Wireshark
Assignee [email protected]
Reporter [email protected]

Build Information:
Version 1.10.7 (v1.10.7-0-g6b931a1 from master-1.10)

Copyright 1998-2014 Gerald Combs <[email protected]> and contributors.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Compiled (64-bit) with GTK+ 2.24.14, with Cairo 1.10.2, with Pango 1.30.1, with
GLib 2.34.1, with WinPcap (4_1_3), with libz 1.2.5, without POSIX capabilities,
without libnl, with SMI 0.4.8, with c-ares 1.9.1, with Lua 5.1, without Python,
with GnuTLS 2.12.18, with Gcrypt 1.4.6, without Kerberos, with GeoIP, with
PortAudio V19-devel (built Apr 22 2014), with AirPcap.

Running on 64-bit Windows 7 Service Pack 1, build 7601, with WinPcap version
4.1.3 (packet.dll version 4.1.0.2980), based on libpcap version 1.0 branch
1_0_rel0b (20091008), GnuTLS 2.12.18, Gcrypt 1.4.6, without AirPcap.
Intel(R) Core(TM) i7 CPU       M 620  @ 2.67GHz, with 8051MB of physical
memory.


Built using Microsoft Visual C++ 10.0 build 40219

Wireshark is Open Source Software released under the GNU General Public
License.

Check the man page and http://www.wireshark.org for more information.
--
Since the network card of the computer supports offloading segmentation of
large TCP/IP frames, frames with a size greater than the MTU are captured by
Wireshark.

Now every time when the local computer sends a frame greater than the MTU, the
TCP corresponding ackowledgement is received earlier in time than the sent TCP
frame, e.g.

No. 1636 (16.996621000s): Transmission Control Protocol, Src Port: ctf (84),
Dst Port: 55697 (55697), Seq: 36821, Ack: 10255, Len: 0, Flags: 0x010 (ACK)

No. 1657 (17.173938000s): Transmission Control Protocol, Src Port: 55697
(55697), Dst Port: ctf (84), Seq: 10255, Ack: 37161, Len: 1982, 0x0018

Of course, the IP addresses of these flows are matching each other (x->y and
y->x).


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