Configuring DSCP Values for QoS

Original instructions

Description

The BMENOC0321 control network module can be configured to use the Different Service Code Point () service in the IP packets. When you enable QoS, the module adds a DSCP value to the IP header of the frame to indicate the frame priority.

NOTE: The BMENOC0321 module supports the OSI layer 3 Quality of Service (QoS) standard defined in IEEE RFC 2475.

Use the QoS page to view or edit the QoS DSCP prioritization values.

Configuration

Configure the QoS service:

Step	Action
1	Enable the QoS Tagging field on the Services page.
2	Expand (+) the Services page to see QoS in navigation tree.
3	Select the QoS node to see the configurable parameters.
4	Enter changes in the appropriate fields on the QoS configuration page. (The table below describes the traffic settings.)
5	Press a button to finish: Apply: Save changes with the window open. OK: Save changes and close the window.

QoS Settings

Use these guidelines to effectively implement QoS settings in your Ethernet network:

Use network switches and routers 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.

Schneider Electric recommends that these QoS values be set in the configuration.

Use the Control Expert to set default values for EtherNet/IP traffic, Modbus TCP Traffic, and the Network Time Protocol traffic:

Field	Traffic	Default
EtherNet/IP Traffic	DSCP Value for I/O Data Scheduled Priority Messages	43
	DSCP Value for Explicit Messages	27
	DSCP Value for I/O Data Urgent Priority Messages1	55
	DSCP Value for I/O Data High Priority Messages1	43
	DSCP Value for I/O Data Low Priority Messages1	31
Modbus TCP Traffic	DSCP Value for I/O Messages	43
Modbus TCP Traffic	DSCP Value for Explicit Messages	27
Network Time Protocol Traffic	DSCP Value for Network Time Protocol Messages	59
1Enable Advanced Mode to access these fields.

(differentiated service code points) This 6-bit field is in the header of an IP packet to classify and prioritize traffic.

A 10 Mb/s, 100 Mb/s, or 1 Gb/s, CSMA/CD, frame-based LAN that can run over copper twisted pair or fiber optic cable, or wireless. The IEEE standard 802.3 defines the rules for configuring a wired Ethernet network; the IEEE standard 802.11 defines the rules for configuring a wireless Ethernet network. Common forms include 10BASE-T, 100BASE-TX, and 1000BASE-T, which can utilize category 5e copper twisted pair cables and RJ45 modular connectors.

(device type manager) A DTM is a device driver running on the host PC. It provides a unified structure for accessing device parameters, configuring and operating the devices, and troubleshooting devices. DTMs can range from a simple graphical user interface (GUI) for setting device parameters to a highly sophisticated application capable of performing complex real-time calculations for diagnosis and maintenance purposes. In the context of a DTM, a device can be a communications module or a remote device on the network.

A network communication protocol for industrial automation applications that combines the standard internet transmission protocols of TCP/IP and UDP with the application layer common industrial protocol (CIP) to support both high speed data exchange and industrial control. EtherNet/IP employs electronic data sheets (EDS) to classify each network device and its functionality.

(Modbus over TCP protocol) This is a Modbus variant used for communications over TCP/IP networks.

TCP/IP-based messaging for Modbus TCP and EtherNet/IP. It is used for point-to-point, client/server messages that include both data, typically unscheduled information between a client and a server, and routing information. In EtherNet/IP, explicit messaging is considered class 3 type messaging, and can be connection-based or connectionless.

(network time protocol) Protocol for synchronizing computer system clocks. The protocol uses a jitter buffer to resist the effects of variable latency.