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Windows 7: Modify DSCP to Layer 2 dot1p mapping for QoS

06 Apr 2017   #1

Windows 7 Enterprise x64 SP1
Modify DSCP to Layer 2 dot1p mapping for QoS

I am a wireless network engineer trying to make improvements on our enterprise network. I posted my original question on the Aruba Networks forum here:

Incorrect DSCP WMM AC mapping on both client and AP - Airheads Community

To summarize, we use Cisco Jabber which marks voice packets with DSCP 46. Windows takes the voice IP packet, assigns it to it's default Layer 2 (802.1p or "dot1p") priority of 5, and sends it out the wireless interface.

We've implemented WMM, which essentially is QoS for wireless. The unfortunate thing about this is that 802.1p and WMM Access Categories are not really the same, but Windows doesn't know the difference, so it uses the dot1p value of 5 when sending out the voice packet. Packets with a priority of 5 are queued like "video" packets, and thus have a lower statistical probability of getting access to the wireless medium than they would if they were marked as priority 6 (the WMM Access Category for voice).

Other devices like Mac and Android are correctly marking their voice packets as priority 6 or 7 (same statical probability as far as wireless QoS is concerned), but Windows 7 is being stubborn.

As I detailed in my original post on the Aruba forum, I've tried using gpedit.msc to set Guaranteed Service Type to 6, but this did not actually happen as revealed by a packet capture. Jabber is the application marking the packet with DSCP 46, and it appears that Windows is using some sort of default mapping that says if we are sending a packet with DSCP 46, mark it with dot1p priority of 5.

I've search high and low for this answer and dug through the registry using various relevant search strings hoping to happen upon the DWORD that could fix this, but have come up empty handed.

So the actual question, does anyone know how to change the DSCP to dot1p mappings that Windows uses?

My System SpecsSystem Spec

 Modify DSCP to Layer 2 dot1p mapping for QoS

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