• Architecture
• Requirements
• Installation and usage
• Features
  • Bandwidth
  • Delay
  • ACM
  • Quality of Service (QoS)
• Docker

Architecture

Trunks is a lightweight DVB-S2/RCS2 satellite system simulator using the native linux tools tc and iptables. The following figure depicts the architecture of the software.

It can run under a single VM or Docker.

Requirements

Hardware: Linux host with two network interfaces UP and configured

Software: tc, iptables, go

Tested using iperf between 2 hosts with the following testbed:

• Trunks running under Ubuntu 18.04 VirtualBox VM 1 CPU 1 RAM, golang 1.16.2
• Host 1 running under Ubuntu 18.04 VirtualBox VM 1 CPU 1 RAM iperf server/client
• Host 2 running under Ubuntu 18.04 VirtualBox VM 1 CPU 1 RAM iperf client/server

Installation and usage

Steps for installation:

git clone https://github.com/shynuu/trunks
go build -o trunk -x main.go

Launch trunks with sudo privilege (required for enabling the forwarding and interacting with iptables/tc):

sudo ./trunk --config config/trunks.yaml --flush --acm --qos

Launch options are detailed below:

NAME:
   trunks - a simple DVB-S2/DVB-RCS2 simulator

USAGE:
   trunk [global options] command [command options] [arguments...]

AUTHOR:
   Youssouf Drif

COMMANDS:
   help, h  Shows a list of commands or help for one command

GLOBAL OPTIONS:
   --config FILE                   Load configuration from FILE (default: not set)
   --logs value                    Log path for the log file (default: not set)
   --flush                         Flush IPTABLES table mangle and clear all TC rules (default: false)
   --acm                           Activate the ACM simulation (default: not activated)
   --qos                           Process traffic using QoS (default: not activated)
   --disable-kernel-version-check  Disable check for bugged kernel versions (default: kernel version check enabled)
   --help, -h                      show help (default: false)

Features

Configuration: change the config config/trunks.yaml file or create a new one.

You need to associate each network interface with a satellite component. The component/interface association is important as it will determine the forward and return link process. Trunks code is based on this script. You can either set the L2 interface name or the IP address of the interface. Both interfaces must already be configured and UP.

nic:
  st: enp0s8
  gw: enp0s9

Bandwidth

You can set the bandwidth (in Mbit/s) for the forward and return link. Minimum required is 2 Mbit/s for the forward and return link.

bandwidth:
  forward: 80
  return: 20

Delay

You can set the delay (in ms) to simulate a LEO, MEO or GEO altitude. The delay changes during the simulation and is comprised between delay - offset <= value <= delay + offset.

delay:
  value: 20
  offset: 10

ACM

When you launch Trunks with the option --acm, the ACM mechanism of DVB-S2/RCS2 systems is simulated.

The maximum bandwidth of the forward and return link will vary according to the values set in the config file:

acm:
  - weight: 1
    duration: 10
  - weight: 0.8
    duration: 10
  - weight: 0.9
    duration: 10
  - weight: 0.5
    duration: 10
  - weight: 0.7
    duration: 10

The program picks a random tuple of this list and weights the maximum bandwidth (forward = weight * forward and return = weight * return) of the link for the specified duration (in seconds). At the end of this duration, it randomly picks another tuple and restarts the process.

Quality of Service (QoS)

You can activate the QoS with the option --qos. Basically the traffic coming in and out of trunks with the PHB EF (DSCP 0x2e) and PHB VA (DSCP 0x2c) will be processed in a dedicated HTB. This HTB has the highest priority value and has a 1 Mbit/s bandwidth reserved.

Docker

You can build the docker image by running this script

Then try the docker-compose example executing the following commands:

cd container
docker-compose up -d

You still must configure the routes inside the client and server containers.

Known issues

Some versions of the kernel are known to crash when offset delay is enabled. As a protection, offset delay is by default disabled if you are running on affected versions. You can bypass protection by using the flag --disable-kernel-version-check, but this is NOT recommended. See this issue for details.