netdev - Re: [E1000-devel] [PATCH] fixing hw timestamping in igb

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Date:	Wed, 9 Feb 2011 10:27:39 +0100
From:	Anders Berggren <anders@...on.se>
To:	Joe Perches <joe@...ches.com>
Cc:	"Ronciak, John" <john.ronciak@...el.com>,
	"Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>,
	e1000-devel@...ts.sourceforge.net, netdev@...r.kernel.org
Subject: Re: [E1000-devel] [PATCH] fixing hw timestamping in igb

On Feb 9, 2011, at 9:56 AM, Joe Perches wrote:

> On Wed, 2011-02-09 at 09:24 +0100, Anders Berggren wrote:
>> Our hardware ping, using Intel 82580 NICs,
>> have an accuracy of 8 nanoseconds.
> 
> Perhaps you mean 8 nanosecond resolution?
> Is documentation available for this claim?

Well, both. 8 ns is the accuracy when performing RTT (round-trip time) measurements using our hardware ping tool. We tested it by connecting a 10 m (European meters ;) CAT6 copper and measuring the jitter. The RTT is always 1240 ns or 1248 ns, hence the accuracy of 8 ns.

$ sudo ./probed -c 10.10.10.3 -i eth2 -p 666
SLA-NG probed 0.1
probed: Binding port 666
probed: Using hardware timestamps
probed: client: ::ffff:10.10.10.3: Connecting to port 666
probed: client: ::ffff:10.10.10.3: Connected
Response    1 from 0 in 1240 ns
Response    2 from 0 in 1248 ns
Response    3 from 0 in 1248 ns
Response    4 from 0 in 1248 ns
^C
4 ok, 0 ts err, 0 lost pong, 0 timeout, 0 dup, 0.000000% loss
max: 1248 ns, avg: 1246 ns, min: 1240 ns

This is our tool: 

$ ./probed 
SLA-NG probed 0.1
usage: probed [-saqd] [-c addr] [-t type] [-i iface] [-p port] [-f file]

	          MODES OF OPERATION
	-c addr   Client mode: PING 'addr', fetch UDP timestamps
	-s        Server mode: respond to PING, send UDP timestamps
	-d        Daemon mode: both server and client, output to pipe

	          OPTIONS
	-k        Create timestamps in kernel driver instead of hardware
	-u        Create timestamps in userland instead of hardware
	-i iface  Network interface used for hardware timestamping
	-p port   UDP port, both source and destination
	-w usecs  Client mode wait time between PINGs, in microseconds
	-v        Output more debugging
	-q        Be quiet, log error to syslog only
	-f file   Path to configuration file

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