The current EtherNet/IP V3/V5 firmwares do not support sending 802.1Q frames on CIP and IEEE 1588 messages.
This functionality shall be added in order to be compatible to previous firmware generations that supported this feature.

Customers in general want to ensure compatibility when updating their product's firmware.
Customers who are using the older V2 firmware generation in their products and need to upgrade the firmware to a new generation (V3/V5), do not want to lose a feature.

User Story Statements

• As a technology provider, Hilscher wants to offer hier customers a broad set of EtherNet/IP functionalities. 
• As a product supplier, I want to ensure compatibility between different product firmware versions, so that the end-user can seamlessly integrate the updated product into an existing system.
• As a product supplier, I want to update my product's firmware, so that it stays compliant to the CIP specification. (rationale for firmware upgrade)

Details

Quality of Service (QoS) is a general term for mechanisms that treat traffic streams with different relative priorities or other delivery characteristics.

Standard QoS mechanisms include IEEE 802.1D/Q (Ethernet frame priority) and Differentiated Services (DiffServ) in the TCP/IP protocol suite.
Within the CIP and EtherNet/IP application context, QoS is especially important for time sensitive applications such as CIP Sync and CIP Motion where packet delivery will affect application stability.

The V3/V5 firmware generations do support DiffServ, but not support 802.1Q (sending of VLAN tagged messages).

Support of 802.1Q is directly linked to QoS attribute 1 "802.1Q Tag Enable".

CIP Volume 2 description of attribute 1 (Edition 1.33):
The "802.1Q Tag Enable" attribute enables or disables sending 802.1Q frames on CIP and  IEEE1588 messages. When the attribute is enabled, the device shall send 802.1Q frames for all CIP and IEEE 1588 messages. The 802.1Q priority value shall be as specified in Volume 2, chapter 3. A value of 1 shall indicate enabled. A value of 0 shall indicate disabled. The default value for the attribute shall be 0. A change to the value of the attribute shall take effect the next time the device restarts.

TODOs in this ticket

• Extend Datasheets: Add an entry in the "Supported features" list.