Configuration

Traffic configuration

The applications itself are configurable. The configuration defines all required parameters such as how many frames are transmitted per cycle, which traffic classes are active, the cycle time, clock and many more.

The configuration is based on YAML files and parsed at startup. Valid configurations have to be created before starting the simulation.

Possible parameters include:

Configuration options

Option

Description

ApplicationClockId (String)

CLOCK_TAI or CLOCK_MONOTONIC

ApplicationBaseStartTimeNS (Integer)

Absolute start time of simulation (or nothing for default value now + 30s)

ApplicationBaseCycleTimeNS (Integer)

Application cycle time

ApplicationTxBaseOffsetNS (Integer)

Execution offset of Tx threads within Application cycle time

ApplicationRxBaseOffsetNS (Integer)

Execution offset of Rx threads within Application cycle time

ApplicationXdpProgram (String)

Application specific XDP program

<Class>Enabled (Boolean)

Selects whether this traffic is active or not

<Class>XdpEnabled (Boolean)

Use XDP instead of RAW sockets

<Class>XdpSkbMode (Boolean)

Use XDP skb mode (for testing XDP code or driver implementation)

<Class>XdpZcMode (Boolean)

Use XDP zero copy mode

<Class>XdpWakeupMode (Boolean)

Use XDP wakeup mode

<Class>XdpBusyPollMode (Boolean)

Drive XDP socket in busy poll mode

<Class>TxTimeEnabled (Boolean)

Use Tx Launch Time for all transmitted frames (requires ETF Qdisc and is not compatible with XDP)

<Class>TxTimeOffsetNS (Integer)

Optional Tx Launch Time offset relative to Qbv schedule and cycle time

<Class>IgnoreRxErrors (Boolean)

By default, the applications perform consistency checks for all received frames. This option disables these checks. Do not enable this. This is only useful for testing e.g., overload scenarios.

<Class>Vid (Integer)

VLAN ID used for traffic generation

<Class>Pcp (Integer)

VLAN PCP used for traffic generation

<Class>NumFramesPerCycle (Integer)

Number of frames transmitted per cycle

<Class>PayloadPattern (String)

Payload pattern for frame content. The payload is a sequence of bytes. If the payload pattern is smaller than the frame size, zero padding is added.

<Class>FrameLength (Integer)

Length of frames excluding four bytes of FCS

<Class>SecurityMode (String)

One of None, AO (Authentication only), AE (Authentication and Encryption)

<Class>SecurityAlgorithm (String)

One of AES256-GCM, AES128-GCM, CHACHA20-POLY1305

<Class>SecurityKey (String)

Key to be used for crypto functions either 16 or 32 bytes depending on selected algorithm

<Class>SecurityIvPrefix (String)

Prefix of the IV which is 6 bytes in size

<Class>RxQueue (Integer)

Receive queue

<Class>TxQueue (Integer)

Transmit queue. This is not used at the moment. Tx queue is determined via SocketPriority. For XDP the socket is bound to RxQueue.

<Class>SocketPriority (Integer): Socket priority

Socket priority. It used for QoS of the operating system.

<Class>TxThreadPriority (Integer)

Tx thread priority based on SCHED_FIFO

<Class>RxThreadPriority (Integer)

Rx thread priority based on SCHED_FIFO

<Class>TxThreadCpu (Integer)

Tx thread CPU affinity

<Class>RxThreadCpu (Integer)

Rx thread CPU affinity

<Class>Interface (String)

Network interface to be used

<Class>Destination (MAC/IP Address)

Destination MAC/IP address

LogThreadPriority (Integer):

Log thread priority based on SCHED_FIFO

LogThreadCpu (Integer)

Log thread CPU affinity

LogFile (String)

Path to log file

LogLevel (String)

Log level, one of Debug, Info, Warning, Error

StatsCollectionIntervalNS (Integer)

Interval in which a summary of the data is generated, typically 1s, i.e. 1000000000Ns

StatsHistogramEnabled (Boolean)

Decides whether a histogram is written after successful run or not

StatsHistogramMinimumNS (Integer)

Lower boundary of RTT which is recorded in histogram e.g., 1ms

StatsHistogramMaximumNS (Integer)

Upper boundary of RTT which is recorded in histogram e.g., 10ms

StatsHistogramFile (String)

Path to file where to store the histogram after run

LogViaMQTT (Boolean)

Enable and disable MQTT logging

LogViaMQTTThreadPriority (Integer)

Thread priority for the logging thread, usually low < 7

LogViaMQTTThreadCpu (Integer)

Thread CPU affinity

LogViaMQTTBrokerIP (IP Address)

IP address where MQTT broker is running

LogViaMQTTBrokerPort (Integer)

Port used by the MQTT Broker, default value is

LogViaMQTTKeepAliveSecs (Integer)

Keep alive time for the connection, default value 60s

LogViaMQTTMeasurementName (String)

Used to distinguish measurements coming from different machines.

DebugStopTraceOnOutlier (Integer)

Stop Linux kernel tracing if round trip or oneway time exceeds expected value

DebugStopTraceOnError (Boolean)

Stop Linux kernel tracing if error happened (e.g. transmission failure)

DebugMonitorMode (Boolean)

Monitor mode for Fraunhofer FPGA measurement

DebugMonitorDestination (MAC Address)

Destination address of first frame per burst

The possible traffic classes are:

  • TsnHigh: TSN Stream High traffic

  • TsnLow: TSN Stream Low traffic

  • Rtc: Real time cyclic traffic

  • Rta: Real time acyclic traffic

  • Dcp: Discovery and basic Configuration Protocol

  • Lldp: Link-Layer Discovery Protocol

  • UdpHigh: Connection traffic Best Effort High

  • UdpLow: Connection traffic Best Effort Low

  • GenericL2: Traffic class to simulate any kind of protocol such as OPC/UA

Note

Not all traffic class have all options available. For instance, only real time traffic classes such as TSN or RT make use of XDP sockets. When the XDP option is enabled the traffic classes utilize AF_XDP instead of AF_PACKET sockets for Ethernet communication.

Note

The GenericL2 traffic class is not PROFINET specific, but rather used to simulate general purpose Ethernet (Layer 2) based protocols such as OPC/UA PubSub. In addition, to the other traffic classes the EtherType is configurable.

Note

The XdpBusyPollMode option requires Linux kernel >= v6.5. Previous Linux kernel version do not support this feature with PREEMPT_RT enabled.

Note

The security settings are only valid for the PROFINET real time traffic classes. Furthermore, the Linux RealTime Communication Testbench demonstrates only one exemplary implementation. The PROFINET security specification is still under development. This implementation is to be used only for performance measurements. For instance, what impact does real time frame encryption and decryption has on quantity structures? Key updates and other mechanisms are not covered.

Sample configuration files are provided for Intel i210, i225/i226 and stmmac.

Starting point for PROFINET TSN:

Starting point for OPC/UA:

At minimum MAC and IP addresses as well as network interface names have to be adjusted.

Network interface configuration

The configuration of network interfaces is crucial. Different NICs have different capabilities such as queue configuration, routing, Qbv, … For instance, the PROFINET specification specifies which traffic class is transmitted and received on which queue. It also defines which Ethernet frames are VLAN tagged and which are transmitted untagged. The configuration of all NIC settings are either performed by tc from iproute2 package or ethtool. That depends on the Linux driver implementation.

The reference applications provides sample scripts in tests/ folder.

These scripts configure multiple settings:

  • Tx queue assignment

  • Rx queue assignment

  • Qbv schedule

  • IRQ coalescing

  • Threaded NAPI mode

  • IRQ and NAPI thread priorities

All of these settings are required for the PROFINET simulation to work properly.

UDP communication

The UDP communication relies on standard sockets. It assumes that corresponding VLAN interfaces have been setup on the system. VLAN interfaces can be created by multiple ways: NetworkManager, Linux Distribution mechanisms or manually.

Example for manual configuration:

ip link add link eth0 name eth0.100 type vlan id 100
ip addr add XXX dev eth0.100

Whenever a UDP packet is transmitted or received on a VLAN network interface the kernel will automatically add or strip the VLAN tag. The PCP value is derived from the socket priority. This mapping between socket priority and PCP values is configurable.

Example:

ip link set eth0.100 type vlan egress-qos-map 0:0 1:1

The configured socket priorities have to match UdpHighSocketPriority and UdpLowSocketPriority in the yaml files.

Note

In case the UDP communication does not work check the VLAN interface configurations. In case it is still not working check whether the system uses a firewall which filters UDP communication on the configured ports.