TCPEVALUATION

Tcpevaluation is a tool to measure the throughput in TCP layer between two
hosts, monitoring the evolution of the congestion window (cwnd) and the slow
start threshold (ssthresh) in TCP.
It can automatically load Linux kernel modules which are missing, supporting
different TCP congestion avoidance algorithms (e.g., NewReno, Cubic, Westwood),
and runs:
- dummynet, in order to emulate a bottleneck between the two hosts, choosing
bandwidth, delay, loss and queue values;
- tcp_probe, for reading cwnd and ssthresh values on the client side;
- iperf, for generating TCP traffic and measuring the throughput;
- gnuplot, for plotting graphs as output.


Requirements:

- two connected hosts;
- same GNU/Linux distribution (tested Linux kernel version: 2.6.32);
- for different versions tcp_probe and dummynet modules must be compiled
  (they are in path tcpevaluation/utility/modules);
- dummynet binaries installed on the server side;
- sudo enabled without asking password for the current user on both hosts;
- OpenSSH client and server on both hosts;
- iperf on both hosts;
- gnuplot on the client host (not mandatory, but recommended);
- tcpevaluation copied on both hosts, preferably in the same path.


Help scripts:

- config.sh can be used on both sides to set up a network interface and
OpenSSH;
- benchmarks.sh is a tutorial provided in order to execute tcpevaluation
multiple times in different settings in a non-interactive mode.


TCP congestion avoidance algorithms

* Get the list of algorithms supported by default or manually loaded:
    cat /proc/sys/net/ipv4/tcp_available_congestion_control
(default for Linux 2.6.32: cubic and reno)

* Get the list of available and allowed algorithms:
    cat /proc/sys/net/ipv4/tcp_allowed_congestion_control
(default for Linux 2.6.32: cubic and reno)

Note: reno is the implementation of TCP NewReno and not of the original Reno.

* Get the default one:
    cat /proc/sys/net/ipv4/tcp_congestion_control
(default for Linux 2.6.32: cubic)

* Get the list of loadable kernel modules related to TCP algorithms:
    /sbin/modprobe -l 'tcp_'
They are automatically loaded by tcpevaluation, if needed. For instance,
for westwood the module tcp_westwood.ko is loaded.


MAIN SCRIPT (tcpeval.sh)

Once network interfaces and OpenSSH are set up on both sides, this tool can
be used on client side executing the script tcpeval.sh in the directory
tcpevaluation. The server host will be automatically configured with SSH.

There are two alternatives: 

1- Interactive mode

./tcpeval.sh


2- Non-interactive mode

./tcpeval.sh -h SERVER_IP -u SERVER_USER -p SERVER_PATH -b BANDWIDTH -t TIME \
    -D -d DELAY -l LOSS -q QUEUE -Z TCP_CONGESTION -c ITERATIONS -F FOLDER_NAME

where:

- SERVER_IP is the IPv4 address of the server. It is mandatory;
- BANDWIDTH is the bandwidth in kbit/s of the bottleneck. It is mandatory;

- SERVER_USER is the username used on server side. It is not mandatory if it is
the same on both sides;
- SERVER_PATH is the path of tcpevaluation on server side. It is not mandatory
if it is the same on both sides;
- TIME is the length in seconds of a single execution of iperf. It is not
mandatory (default: 30 seconds);
- -D refers to dummynet, used by default. Netem is available as well, using -N,
but it has not been tested very much and does not support queues;
- DELAY is the delay of the bottleneck in milliseconds. It is not mandatory
(default: 0 ms);
- LOSS is the ratio of losses in [0,1] range. It is not mandatory (default: 0);
- QUEUE is the size of the queue in number of IP packets. It is not mandatory
(default: 0);
- TCP_CONGESTION is the TCP congestion avoidance algorithm used by iperf. It is
not mandatory (default: the current one);
- ITERATIONS is the number of iterations to do for the test. It is not
mandatory (default: 1);
- FOLDER_NAME of the output.


Examples

Server IPv4: 192.168.1.1
Client IPv4: 192.168.1.2
same user and path on both hosts
using dummynet (default)

* Bandwidth 10 Mbit/s = 10240 Kbit/s - only mandatory argument (delay: 0 ms,
    loss: 0, queue: 0, TCP congestion avoidance algorithm: current)
./tcpeval.sh -h 192.168.1.1 -b 10240

* Bandwidth 1 Mbit/s and delay 10 ms (loss and queue: 0, TCP alg.: current)
./tcpeval.sh -h 192.168.1.1 -b 1024 -d 10

* Bandwidth 5 Mbit/s and loss 2% (delay and queue: 0, TCP alg.: current)
./tcpeval.sh -h 192.168.1.1 -b 5120 -l 0.02

* Bandwidth 10 Mbit/s, delay 20 ms and queue 200 (loss: 0, TCP alg.: current)
./tcpeval.sh -h 192.168.1.1 -b 10240 -d 20 -q 200

* Bandwidth 10 Mbit/s, loss 1% and TCP NewReno (delay and queue: 0)
./tcpeval.sh -h 192.168.1.1 -b 10240 -l 0.01 -Z reno

* Bandwidth 10 Mbit/s, delay 50 ms, queue 500, TCP Cubic (loss: 0)
./tcpeval.sh -h 192.168.1.1 -b 10240 -d 50 -q 500 -Z cubic


For advanced options:

./tcpeval.sh -h