Description

The M580 CPU can be configured to perform Ethernet packet tagging. The CPU supports the OSI layer 3 quality of service (QoS) standard defined in RFC-2475. When you enable QoS, the CPU adds a differentiated services code point (DSCP) tag to each Ethernet packet that it transmits to indicate the priority of that packet.

QoS Tab

The QoS tab is available only on CPUs that do not support the RIO scanner service (only on CPUs with commercial references that end with 20).

Field

Parameter

Value

Comment

DSCP Tagging

–

Enabled

default

Disabled

–

PTP

DSCP PTP Event Priority

59

–

DSCP PTP General Priority

47

–

EtherNet/IP Traffic

DSCP Value For I/O Data Schedule Priority Messages

47

–

DSCP Value For Explicit Message

27

–

DSCP Value For I/O Data Urgent Priority Messages

55

–

DSCP Value For I/O Data High Priority Messages

43

–

DSCP Value For I/O Data Low Priority Messages

31

–

Modbus TCP Traffic

DSCP Value For I/O Messages

43

–

DSCP Value For Explicit Message

27

–

Network Time Protocol Traffic

DSCP Value For Network Time Protocol Messages

59

–

DSCP tagging lets you prioritize the Ethernet packet streams based on the type of traffic in that stream.

To implement QoS settings in your Ethernet network:

  • Use network switches that support QoS.

  • Consistently apply DSCP values to network devices and switches that support DSCP.

  • Confirm that switches apply a consistent set of rules for sorting DSCP tags, when transmitting and receiving Ethernet packets.