Re: [tsvwg] Windows10 and DSCPs

[Greg White <[e-mail]>]

Hi Sebastian,

Thanks for performing that testing and reporting the result.  I was under the impression that those settings were only available for Windows domain joined machines (managed by an IT administrator).  Are we safe to assume that this also works for DSCP 45?  If so, this could be useful for testing.

-Greg



On 12/15/23, 9:04 AM, "tsvwg on behalf of Sebastian Moeller" <[e-mail] <mailto:[e-mail]> on behalf of moeller0=[e-mail] <mailto:[e-mail]>> wrote:


Dear Greg, dear list


we had a few discussions about the usage of DSCPs under windows (e.g. recently in the comments of the Domos Latency seminar). 


The current NQB draft addresses this here:


• Traffic that is compliant with the NQB sender requirements Section 4.1 is unlikely to cause more degradation to lower priority Access Categories than the existing recommended Video Access Category traffic types: Broadcast Video, Multimedia Streaming, Multimedia Conferencing from [RFC8325], and AudioVideo, ExcellentEffort from [QOS_TRAFFIC_TYPE].




which refers to
[QOS_TRAFFIC_TYPE] Microsoft, Corporation, "QOS_TRAFFIC_TYPE enumeration", 2022, <https://learn.microsoft.com/en-us/windows/win32/api/qos2/ne-qos2-qos_traffic_type> <https://learn.microsoft.com/en-us/windows/win32/api/qos2/ne-qos2-qos_traffic_type&gt;>. 


A website that seems to imply that windows only offers access to a limited set of DSCPs. That seems not incorrect for applications using the qos2 header, but this is not the only way to assign DSCPs under windows. There is the group policy editor as well as XXX-NetQosPolicy under powershell:


Here I went and just tested whether I can use the following instructions to assign different DSCPs to ssh traffic from putty:


# windows QoS: https://docs.microsoft.com/en-us/powershell/module/netqos/?view=win10-ps <https://docs.microsoft.com/en-us/powershell/module/netqos/?view=win10-ps>
New-NetQosPolicy -Name "putty" -AppPathNameMatchCondition "putty.exe" -PolicyStore ActiveStore -NetworkProfile All -DSCPAction 46


Seems to work, and I confirmed via wireshark that putty's ssh packets actually use DSCP 46 (aka EF). I note that powershell needs to be run as administrator, and the policies do not end up visible in Local Group Policy Editor.




I also tried DSCP values 41, 42, 56 (CS7), and 51 and confirmed with wireshark on the windows10 hosts ethernet interface that outgoing TCP packets with source port 22 carried the expected DSCP value.


I only have windows 10 pro (version 22H2) available and did not test windows 11 at all, but at least for my version of it appears that all DSCPs are available, albeit under the administrator's control and not the application.




Best Regards
Sebastian