Simple but powerful tool for troubleshooting networks

There are a few tools available to measure network performance metrics just as throughput, packet loss and jitter. One tool I have used from place to place is an open source tool called iperf. This piece of software is simple to run, however provides enough options and information to enable you to troubleshoot network issues.

Before starting, a quick review of the transport layer: An application using the transport layer can use TCP or UDP depending on the application requirements. In general, if the application requires error free in-order delivery of packets, at that time TCP is best. If the application can tolerate some packet loss, at once UDP will probably fit the requirements. The two types of transport protocol each have their uses. The difference with TCP as opposed to UDP is that TCP may be slower than UDP for packet delivery. Opposite, UDP may be faster, however it makes no guarantee that the packets will arrive at the destination. Email and web browsing use TCP. VoIP (Voice over Internet Protocol) can tolerate some packet loss and in a nutshell uses UDP.

The area of interest on TCP is bandwidth

The area of interest on TCP is bandwidth. In this example we have two laptops on the same subnet. One laptop is connected via wired Ethernet, whereas the second laptop is connected via an 802.11g wireless router. The theoretical bandwidth for 802.11g is 54MBits/sec. The output from the server side is as below.

In this case, there is no packet loss. For both runs, the jitter is as a general rule less than 1ms, which is within the tolerance levels of VoIP.

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