tcServiceForRaspberry

The code and configuration files in this repository enable a raspberry pi to open a wlan which can be throttled by REST API calls. We use raspberry pis with traffic shaper to measure the performance of web applications with mobile devices and WebPagetest.

Installation

As WLAN adapter we use an "Edimax EW-7811Un".

Installation Raspbian

1. Download Raspbian from here
2. Install Raspbian like described here on SD card.

Configure User

1. Add a user trafficshaper

    sudo useradd trafficshaper
   

2. Grant sudo rights by adding to /etc/sudoers

    trafficshaper ALL=(ALL) NOPASSWD: ALL
   

Install Python module

1. Download module

    cd ~
    wget http://webpy.org/static/web.py-0.37.tar.gz
   

2. Install

    tar -zxvf web.py-0.37.tar.gz
    cd web.py-0.37
    sudo python setup.py install
   

Install and configure hostapd

1. Install hostapd

    sudo apt-get install hostapd
   

2. Replace binary /usr/sbin/hostapd with hostapd file from this repository (usr/sbin/hostapd)

3. Replace line

    #DAEMON_CONF
   

in file /etc/Default/hostapd with

    DAEMON_CONF="/etc/hostapd/hostapd.conf"

4. Config file /etc/hostpad/hostapd.conf should contain the folllowing:

    interface=wlan0
    driver=rtl871xdrv
    ssid=[SSID-of-your-wlan]
    hw_mode=g
    channel=6
    macaddr_acl=0
    auth_algs=1
    ignore_broadcast_ssid=0
    wpa=2
    wpa_passphrase=[ssid-pasword]
    wpa_key_mgmt=WPA-PSK
    wpa_pairwise=TKIP
    rsn_pairwise=CCMP
   

Adapt "ssid" and "wpa_passphrase" if necessary.

Service hostapd should be started with each reboot now.

Install dnsmasq

1. Install dnsmasq

    sudo apt-get install dnsmasq
   

2. Copy files etc/resolv.conf und etc/dnsmasq.conf of this repository to /etc/-Folder

3. Restart service

    sudo service dnsmasq restart
   

Service dnsmasq should be started with each reboot now.

Install traffic shaping REST API

1. Copy the following files from this repository to /opt/trafficshaper

    rest.py
    trafficshaper_init.sh
    configure_traffic_control.sh
   

2. Add trafficshaper scripts to autostart

   1. Copy template trafficshaper from this repository to /etc/init.d/

   2. Make scripts executable (chmod +x)

       chmod +x /opt/trafficshaper/*.*
      

   3. Add scripts to run-level

       update-rc.d trafficshaper defaults
      

Configuration and usage

Configure default throttling

With each start of raspberry pi throttling starts with default values for the following parameters:

• bwdown download bandwidth (kbit/s)
• bwup upload bandwidth (kbit/s)
• latencydown latency delay download (ms)
• latencyup latency delay upload (ms)
• plrdown Packet loss rate download
• plrup Packet loss rate upload

One can change default throttling in last three lines of file /opt/trafficshaper/rest.py

Set throttling via HTTP GET request

Parameters of REST API call get explained if you call

http://<IP adress-of-raspberry-pi>:8080/

Example call:

http://localhost:8080/set_shaping?bwdown=4000&bwup=2000&latencydown=40&latencyup=50&plrdown=0.0&plrup=1

This call would set...

• a bandwidth of 4.000 kBit/s downstream,
• a bandwidth of 2.000 kBit/s upstream,
• 40ms latency delay for downstream,
• 50ms latency delay for upstream,
• 0,0% packet loss rate downstream and
• 1,0% packet loss rate upstream.

So round trip time of single tcp packets would get extended by 90ms. One percent of packets get lost on this round trip.