ipbench - latency test

About the test

The ipbench latency test allows you to measure latency between a number of distributed clients and a target device.
The aim is to keep the load on each client low, so it can make accurate measurements, regardless of the load on the target.

Running the test

Client Machine

The client machine need only be running the ipbenchd daemon.

Controller

Running the test

There are a number of options that can be passed to the test. The options should be passed with the --test-args command line paramater in a simple "command=value,command1=value1" format (note no whitespace). The test options are

Argument	Description	Example	Default	Notes
bps\|Mbps	Throughput to attempt in bits per second or millions of bits per second for each client (i.e. total to attempt is this argument * number of clients)	bps=100000000 Mbps=100	10Mbps
size	Size of message in bytes	size=1024	100	Small packet sizes will increasingly not work with increasing throughputs. Experimentation is best, but be careful about things like fragmentation that may effect results.
sockopts	Set socket options on the client. You can currently set most standard socket options with this command. See the socket (7) man page for more details about these options. SO_KEEPALIVE SO_REUSEADDR SO_BROADCAST SO_NODELAY SO_LOWDELAY SO_THROUGHPUT SO_SNDBUF=number SO_RCVBUF=number SO_SNDLOWAT=number SO_RCVLOWAT=number SO_SNDTIMEO=number SO_RCVTIMEO=number Options should be separated with a semi-colon (;)	sockopts=SO_NODELAY;SO_RCVBUF=16384	N/A
warmup	Warmup time in seconds	warmup=20	5	If you are using the companion test, make sure you pass the same warmup and cooldown times with the --target-args command so the target knows what results to ignore.
cooldown	Cooldown time in seconds	cooldown=20	5
socktype	Socket type (UDP or TCP)	socktype=udp	tcp
drop	Time before considering a UDP packet dropped, in seconds	drop=5	2

Test output

The test output is a simple list of comma separated numbers in the following format

Requested Throughput,Achieved Throughput,Sent Throughput,Packet Size,Min,Avg,Max,Standard Deviation,Median

Measure	Description	Units	Notes
Requested Throughput	The throughput requested with the bps argument	bits per second
Achieved Throughput	(The number of packets received * the packet size) / (test time)	bits per second	Each client works out its achieved throughput, the total shown is the sum of each client's individal throughput
Sent Throughput	(The number of packets sent * the packet size) / (test time)	bits per second	This allows you to determine two things If the sent throughput is not almost exactly equal to the requested throughput, then the sending machine (s) could not keep up with the requested rate. If the sent throughput is not almost exactly equal to the achieved throughput then the other end is dropping packets and hence can not keep up.
Packet Size	Size of packets sent	bytes
Min	Minimum latency measured	microseconds	Each client returns all of its data to the controller where these figures are calculated.
Avg	Average latency measured	microseconds
Max	Maxiumum latency measured	microseconds
Standard Deviation	Standard deviation of measured latencies.	microseconds
Median	Median latency	microseconds

Target Machine

The target machine need only be running a standard echo service. There are a number of ways you can achieve this.

Enable the echo service via inetd

Many distributions have echo disabled by default. To enable it make sure you have lines like the following in /etc/inetd.conf

#:INTERNAL: Internal services
echo            stream  tcp     nowait  root    internal
echo            dgram   udp     wait    root    internal

By default this will run on port 7.

There are two included stand-alone echo servers, tcp-echo and udp-echo. These are in doc/programs

If you want to measure CPU usage on the target machine with the latency companion test, the ipbenchtd daemon must be running on it. Specify the hostname of the target machine with the --target option, and pass in arguments via --target-args. There are only two arguments, warmup and cooldown; these should be passed as mentioned above.

Example

See the example run