netdev - Re: UDP regression with packets rates

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 9 Sep 2009 13:26:22 -0400 (EDT)
From:	Christoph Lameter <cl@...ux-foundation.org>
To:	Eric Dumazet <eric.dumazet@...il.com>
cc:	netdev@...r.kernel.org
Subject: Re: UDP regression with packets rates < 10k per sec

On Wed, 9 Sep 2009, Eric Dumazet wrote:

> I have no idea how you run the test then, and how are computed time deltas.
>
> Are you clocks synchronized to less than one us ? How is it done ?

Packets are sent one way and include a timestamp. Once in a while (probe
interval) a packet is sent back to the sender (with the timestamp the
sender took earlier). The sender takes a second timestamp and
calculates the latency by dividing by two.

Seen this approach in multiple middleware test programs. Clocks are
typically not synchronized enough to actually compare timestamps from two
systems.

--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html