How to use 4DIAC's Time Sensitive Networking Communication Interface

Introduction

This tutorial shows how to use 4diac's Time Sensitive Networking (TSN) features. Some standards of TSN are still in the active standardization phase (status July 2018) e.g., IEEE802.1ASRev and IEEE802.1Qch. The advantages of TSN are:

Convergent network: network traffic with a vast variety of network requirements are transmitted on a single network cable, hence TSN improves bandwidth utilization and reduces cabling effort.
Interoperability: TSN is an IEEE standard extension for the already existing and broadly used Ethernet.
Determinism: A correctly configured TSN network guarantees the transmission of packets to the appropriate receivers.
Real-Time: On top of determinism TSN networks guarantee the transmission of network packets within a certain time i.e., a maximum latency.

4diac's communication layer implements publish-subscribe connections via Service Interface Function Blocks (SIFB). The publish FBs extended by a VLAN ID and the message priority, represented in the ID data input parameter.

Limitations

The current implementation was tested on Beaglebone Blacks on debian with real-time patch (4.1.27-bone-rt-r22) and Ubuntu 16.04LTS.

Current limitations

TSN layer is supported on Linux
Only supports vlan interfaces with eth0 as its physical network interface (e.g., eth0.1, eth0.2, .. , eth0.165, ..)

How to Build FORTE with TSN Features

Checkout the develop branch of forte
$ git clone https://github.com/eclipse-4diac/4diac-forte.git $ cd org.eclipse.4diac.forte $ git checkout develop
Create a directory for the binary files and set the appropriate CMake variables
$ mkdir -p bin/posix $ cd bin/posix/ $ cmake ../.. -DCMAKE_BUILD_TYPE=Debug -DFORTE_ARCHITECTURE=Posix -DFORTE_COM_TSN=ON
Build forte with:
$ make
Run forte with:
$ cd src $ ./forte

Configure 4diac's TSN Layer Using a Publish Function Block

The new 4diac TSN enabled IP communication layer maps a UDP stream to a specific VLAN interface. It binds the stream to a virtual Ethernet adapter (e.g., eth0.x). The correct tagging with VLAN ID and priority is used by the TSN enabled network to transmit packets according to their real-time requirements. The different VLANs are related to different forwarding and scheduling strategies of the TSN network.

An example of a TSN enabled PUBLISH FB with a standard IP layer SUBSCRIBER FB is shown in the following figure.

Note: In order to make this example work you have to route the UDP multicast traffic at the device of the subscriber like follows:

$ route add -net 239.1.0.0 netmask 255.255.0.0 dev eth0.3 $ ./forte

... and you have to set up the VLAN interface and its IP address on the sending device before binding a stream to it for example via:

$ sudo ifconfig eth0.3 up $ sudo ifconfig eth0.3 "your_favorite_IP_address" $ sudo ifconfig eth0.3 netmask "your_favorite_netmask"

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