Measuring Network Throughput With ttcp

Measuring Network Throughput With ttcp

The ttcp tool measures network throughput. It provides a realistic measurement of network performance between two stations because it allows measurements to be taken at both the local and remote ends of the transmission. As with all network management tools, the statistics must be interpreted with the network configuration and applications in mind. For example, the statistics generated from a ttcp probe between two stations with routers in between results in lower throughput than if the stations were located on the same network. On the same note, users running applications that transmit large data structures see slower throughput than users running applications that transmit smaller data structures.

In any case, on a relatively quiet network, you should expect to see throughput in the 700 KBps or greater range. Throughput of 500 KBps or less is questionable, and 400 KBps or less may indicate a definite network problem.

The following example illustrates the statistics you might see if you ran a simple ttcp test between the stations sheridan and longstreet (two workstations) on a clean network. See the ttcp(1) reference page for details about the many ttcp options.

On sheridan, give the command

ttcp -r -s

You see the following output:

ttcp-r: buflen=8192, nbuf=2048, align=16384/0, port=5001 tcp
ttcp-r: socket ttcp-r: accept from 192.102.108.4
ttcp-r: 16777216 bytes in 19.99 real seconds = 819.64 KB/sec +++
ttcp-r: 10288 I/O calls, msec/call = 1.99, calls/sec = 514.67
ttcp-r: 0.1user 3.4sys 0:19real 17%

On longstreet, enter the command

ttcp -t -s sheridan

You see the following output:

ttcp-t: buflen=8192, nbuf=2048, align=16384/0, port=5001 tcp  -> sheridan
ttcp-t: socket
ttcp-t: connect
ttcp-t: 16777216 bytes in 19.98 real seconds = 820.02 KB/sec +++
ttcp-t: 2048 I/O calls, msec/call = 9.99, calls/sec = 102.50
ttcp-t: 0.0user 2.3sys 0:19real 12%

The throughput statistics are highlighted in bold and are in units of KBps. The throughput on the station sheridan is 819.64 KBps and the throughput on the station longstreet is 820.02 KBps. Both throughput values indicate good network performance between the stations.