423   Default VLAN ID 0

Created: 02 Oct 2006

Status: In Force (green)

Part: Part 9-2 (2004)

Links:

Page: 14

Clause: 5.3.3

Paragraph: Table 7

Category: Issue for edition 2 of this part

Issue

IEC 61850-9-2 Table 7 specifies the default VLAN ID is 0.
Acccording to IEEE 802.1Q table 9-2 the VLAN ID 0 = "The null VLAN ID. Indicates that the tag header contains only user_priority information; no VLAN identifier is present in the frame. This VID value shall not be configured as a PVID, configured in any Filtering Database entry, or used in any
Management operation."
As such VLAN ID 0 should be not used!

Proposal

Use a default VID value other then 0-1-FFF.

Discussion Created Status
VID is configurable and has a default value of 0.
Switch may remove the VLAN header when forwarding the information to an IED. Therefore subscriber implementations must be aware that the VLAN header migth be missing. However, publisher must provide the VLAN Header.
Network guideline already described the use of VLAN ID for reducing the traffic load within a network segment.
03 Nov 11 Ballot Period
Use of VID 0 is technically valid and makes sense in many applications of 61850. However, VID 0 has two serious limitations:

1. Ethernet switches that are 'VLAN aware' may modify GOOSE messages on egress from the switch. The VID may be changed to the default PVID (port VLAN ID) so that the message belongs to a valid VLAN. The destination IEDs may reject the GOOSE message if the message is parsed in a very strict manner i.e. checking for VID=0. Some switches support a 'VLAN unaware' mode of operation but this usually not the default.

2. VID 0 precludes the use of the VLAN concept in a 61850 network. VLANs can play an important role in segregating ethernet traffic in a SS LAN. For example, GOOSE traffic and sampled values(SV) could both be isolated to their own VLANs. This has the significant advantage of reducing the traffic load of IEDs not particpating in GOOSE or SV; SV traffic has been known to cause unininvolved IEDs to malfunction. It also more readily allows station bus and process bus to co-exist on the same physical network. There are also benefits for SS-SS communications whereby WAN protocols like VPLS will allow a more seamless network path for GOOSE and SV.

I suggest ammending the 61850 sections pertaining to VID so that it recommends having a configurable VID for IEDs. The default can remain at 0. I also suggest a recommendation that GOOSE and sampled values have an independent configuration for VID.
02 Feb 07 Discussion (red)
The support of VLANs is not mandatory in IEC 61850-9-2. Therefore, a VLAN ID of 0 (which means that VLANs are not supported) is acceptable. However, all clarifications according to TISSUE 290 for 8-1 shall be added as well. 02 Oct 06 Discussion (red)

 

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