Wireshark-bugs: [Wireshark-bugs] [Bug 10722] New: Round-Trip Time Graph plots incorrect values
| Bug ID |
10722
|
| Summary |
Round-Trip Time Graph plots incorrect values
|
| Product |
Wireshark
|
| Version |
1.10.11
|
| Hardware |
x86
|
| OS |
Windows Vista
|
| Status |
UNCONFIRMED
|
| Severity |
Normal
|
| Priority |
Low
|
| Component |
GTK+ UI
|
| Assignee |
bugzilla-admin@wireshark.org
|
| Reporter |
Jim@agdatasystems.com
|
Created attachment 13281 [details]
Trace with one ACK packet covering 20 data packets.
Build Information:
Version 1.10.11 (v1.10.11-0-g1a5c8ab from master-1.10)
Copyright 1998-2014 Gerald Combs <gerald@wireshark.org> 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 (32-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, with MIT Kerberos, with GeoIP, with
PortAudio V19-devel (built Nov 12 2014), with AirPcap.
Running on 32-bit Windows Vista Service Pack 2, build 6002, 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, with AirPcap 4.1.1 build
1838.
AMD Athlon(tm) 64 X2 Dual Core Processor 4000+, with 1917MB of physical memory.
Built using Microsoft Visual C++ 10.0 build 40219
--
Round-Trip Time is the time between a data packet and an ACK packet sent IN
RESPONSE TO that data packet. ACKs are cumulative, and due to Delayed ACK, an
ACK can acknowledge multiple data packets, but only the time between the last
data packet in the series (the one that actually triggered the ACK) and the ACK
is a valid RTT. However, Wireshark plots a dot on the Round-Trip Time graph for
every data packet, not just the one that triggered the ACK.
The attached trace shows 20 data packets followed by a single ACK that
cumulatively acknowledges all 20 data packets. Plotting a Round-Trip Time graph
shows 20 dots, one for each data packet. (The first one, against the left-hand
edge of the graph, is difficult to spot.) The 20 dots show the RTT decreasing
as the data packets get closer to the ACK, but only the last dot represents a
valid RTT value. Only packet 21 has a tcp.analysis.ack_rtt field.
Wireshark should show one plot point for each ACK packet that is in response to
a data packet (has a tcp.analysis.ack_rtt field), instead of one plot point for
each data packet.
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