[tsvwg] iperf2 Android client: Bounceback fix and updated APK

bob.mcmahon@umbernetworks.com Tue, 21 July 2026 22:56 UTC

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Date: Tue, 21 Jul 2026 15:56:48 -0700
From: bob.mcmahon@umbernetworks.com
To: Ccwg <ccwg@ietf.org>, Iccrg <iccrg@irtf.org>, Ippm <ippm@ietf.org>, Tsvwg <tsvwg@ietf.org>, Hackathon <hackathon@ietf.org>
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Subject: [tsvwg] iperf2 Android client: Bounceback fix and updated APK
Archived-At: <https://mailarchive.ietf.org/arch/msg/tsvwg/29b9QAKNIVYyIMw43SSrscCv8j0>

Hi All,

Following up on the iperf2 Android client I shared earlier.

Several testers found a Bounceback bug. During responsiveness and RPS 
testing under working load, the test would run for a few seconds and 
then fail. The issue is fixed and has been verified with a 50-second 
Bounceback run under load. (reminder, the public servers have a 60 
second maximum - please keep your duration to lesser.)

Install the updated APK

Download this file from the SourceForge file listing:

iperf2.2.2_21July2026_android.apk

https://sourceforge.net/projects/iperf2/files/

Please select that exact filename rather than the green Download button, 
which may retrieve a different default file.

You can install it over an existing version or use it for a new 
installation. Point the app at one of the default responde.* servers or 
your own iperf2 server, select a test mode, and press Start.

Two features worth testing

Bounceback RTT and RPS

Bounceback now displays the minimum RTT reported by the kernel's TCP 
statistics for the connection. This is shown under the live RPS chart 
together with a theoretical RPS ceiling:

1000 / minimum TCP RTT in milliseconds

The two measurements come from different layers. Minimum RTT is a TCP 
statistic, while observed RPS is measured from the application-level 
Bounceback request and reply exchanges.

Because each Bounceback request waits for its reply before the next 
request is sent, the minimum TCP RTT provides a useful lower-bound 
reference for the request and reply cycle. The calculated value is 
therefore a theoretical ceiling, not an expected RPS result. Comparing 
it with observed RPS helps show how much additional time is being 
introduced by server processing, application scheduling, working load, 
and other path effects.

IPv6 testing

The public responde.* servers in Fremont, Vienna, and Newark now support 
IPv6.

The app can use them normally through the Host field. A new Force IPv6 
(-V) option is also available when you want to test the IPv6 path 
explicitly rather than allow the operating system to select the address 
family.

Thanks again to everyone for helping with this and providing feedback.

Bob

[tsvwg] iperf2 Android client: Bounceback fix and… bob.mcmahon