2008 Nov 24 - Mon

TTCP: Test TCP

A quick and simple tool for link bandwidth testing (aka Throughput Testing) is included in many flavours of Cisco's IOS. Although it is hidden and officially unsupported, it is documented and functional.

By running 'ttcp' from the command line in privileged mode on two different routers, one can test links between the routers.

Cisco documents the tool with Document 10340, Using Test TCP (TTCP) to Test Throughput.

A couple of other non-Cisco tools are available and maintain compatibility in order to perform link testing between most combinations of routers, Unix, Linux, and Windows platforms.

Netcordia has a Java based client, while Unix and Windows based client can be found at ttcp. The source compiled on Linux with no problem.

In The Story of the TTCP Program, Mike Muuss discusses some of the history of ttcp. It seems that he is the original author of the venerable ping program. In the same article, Mike illustrates a clever file transfer capability of ttcp, if effect being a UNIX "pipe" between two machines across a network. On the destination machine:

ttcp -r | tar xvpf -

and on the source machine:

tar cf - directory | ttcp -t dest_machine

and on possible intermediate machines:

ttcp -r | ttcp -t next_machine

A discussion of additional variants of ttcp can be found at ttcp/nttcp/nuttcp/iperf versions. It looks as though the version used by Cisco is a renamed nttcp. A version called nuttcp will echo traffic back.

iperf uses the same concept but uses a different name and includes different functionality for network perforamance analysis. I'm not sure if it is compatible with ttcp.

When using iperf, the -P option will run multiple tcp tests simultaneously. A document called Guide to Bulk Data Transfer over a WAN describes the use of iperf to determine data transfer rates under various scenarios.

Linux.com has an article called Benchmarking network performance with Network Pipemeter, LMbench, and nuttcp by Ben Martin.