Bandwidth Estimator is yet another Linux-tool for estimating available bandwidth. It was developed out of frustration with iperf, as well as a desire to easier get a look into how packets are received. The latter is especially important in mobile broadband networks, as they are both statefull and full of middleboxes that often do nasty things. On the machines I have tested, the generator is able to send packets at up to 950 Mbit/s.
Bandwidth estimator consists of two application, a receiver and a traffic generator, and, unlike iperf, only the generator is required to have a public IP (or an IP accessible from the receiver). The receiver instructs the traffic generator by providing desired bandwidth, duration of the test and so forth. The application supports both UDP and TCP, and IPv4 and v6, but is currently limited to downlink measurements. Uplink is at the top of the todo-list.
By providing the receiver with a file name, the arrival time of each packet is written to a file. This can be processed using the included python-script (plot_recv_times.py), which accepts an interval (in ms) and the log file name as input parameters. It then sums up how many bytes were received for each interval (including empty intervals).
Both the raw and the parsed file are easy to plot and enables easy spotting of network artifacts, like buffering. The latter occurs frequently in mobile broadband networks, for example when a device moves or a channel becomes congested. Kernel timestamps are used with UDP, while userspace timestamps are applied to TCP due to its stream nature. If a higher timestamp-resolution is needed, for example tcpdump can be used.
In order to compile the application using the provided Makefile, CMake is required. Otherwise, there are no external dependencies.
The receiver accepts the following command line options:
- -b : Bandwidth in Mbit/s (required).
- -t : Duration of tests in seconds (required).
- -l : Payload length in bytes, only required with UDP.
- -s : Source IP to bind to (required).
- -d : IP of traffic generator (required).
- -p : Port at traffic generator (required).
- -r : Use TCP instead of UDP (optional).
- -w : Filename for writing packet timestamps (optional).
The generator accepts the following command line options:
- -s : Source IP to bind to (required).
- -p : Source port (required).
Worth notin is that the generator creates a thread pool and serves one receiver per thread. If you want to change the number of threads, change the value of NUM_THREADS at the top of bw_estimation_generator.c