Created: 11 Feb 2006
Status: In Force (green)
Part: Part 8-1 (2004)
Clause: Annex C
Issue: In IEC 61850-8-1, Annex C, it is mentioned, that the use of VLAN support is optional. If the mechanism is used, the VLAN ID (VID) shall be set by configuration; if the mechanism is not used, it shall be set to 0.
This specification is ok. However, it has to be noted, that a switch supporting VLANs will alter the tag with a VID=0 by replacing this with the configured default VID, which can not be 0. As a consequence, a device that is not supporting the VLAN mechanism, may expect to receive frames with a VID=0. If the device can not be configured to receive a specific VID, it has to ignore the value of the VID field.
Proposal: Add a note to that paragraph that gives this hint. I.e. the note could read as follow:
NOTE 3: As a switch supporting VLANs will alter tags with a VID=0 by setting the VID value to the configured default VID value for that port, an IED receiving tagged frames shall not expect this frame having a specific VID. That means, if an IED is not supporting to be configured to receive messages with a specific VID, it has to ignore the value of the VID field.
Consider to add a further note, that it is recommended to support VLAN configuration in IEDs for sending messages.