SOURCEFORGE » RALF » 2015 Improving TCP over satellite QoE

2. Simulation program¶

2.1. Simulation¶

First simulation as been run without modem.

Step 1. Configuration of both PC engines. Line commands to configure the PC engines are described in part II.3.

Step 2. Addition of space delay to user interface and hub interface.
tc qdisc add dev p5p1 root netem delay 300ms

Step 3. Test connection and delay from 192.168.2.1 to 192.168.3.1
ping 192.168.3.1 -I 192.168.2.1

Step 4. Implementation of routing rules in order to use PEPSal. Indeed PEPSal uses port 5000, consequently TCP flow must be redirected on this port.

iptables -t mangle -A PREROUTING -s 192.168.2.1 --proto tcp --tcp-flags ALL SYN -j QUEUE
iptables -t nat -A PREROUTING -s 192.168.2.1 --proto tcp -j REDIRECT --to-port 5000
iptables -t mangle -A PREROUTING -d 192.168.2.1 --proto tcp --tcp-flags ALL SYN -j QUEUE
iptables -t nat -A PREROUTING -d 192.168.2.1 --proto tcp -j REDIRECT --to-port 5000


Display all rules to verify
iptables -t mangle -t nat -L

Step 5. Execution of PEPSal on remote terminal side.
pepsal -a 192.168.2.1

Then a TCP flow is simulated thanks to the iperf command.

2.2. Post processing¶

In order to get information on TCP packets, the tcpdump commmand is executed. The save option is run and data are collected in a file.pcap.
Command is:
tcpdump tcp -w fileName.pcap

Files transfert from PC engine right to local computer as following:
scp labo@192.168.0.201:Proj3/*.

The file generated by tcpdump command is compatible with wireshark. Wireshark is a free network protocol analyzer. It lets you see what's happening on your network at a microscopic level. Thanks to this tool, we could compare with and without PEPSal:

• throughput,
• sequence number packets,
• windows size evolution.

Tests in terms of quality of usage, such as download a web browser, were planed. However due to difficulties in network configuration, those tests will not be run.