[cifs-protocol] [EXTERNAL] is MS-DRSR 4.1.10.5.21 CompressOrDecompressWin2k3 the same as MS-WUSP 2.1.1.1 CompressOrDecompressWin2k3 ? - TrackingID#2512240040003184

[Tom Jebo]

[dochelp to cc]
[support mail to cc]

Hi Douglas,

Thanks for your request regarding MS-DRSR 4.1.10.5.21 and MS-WUSP 2.1.1.1. One of the Open Specifications team members will respond to assist you. In the meantime, we've created case 2512240040003184 to track this request. Please leave the case number in the subject when communicating with our team about this request.

Best regards,
Tom Jebo
Microsoft Open Specifications Support

-----Original Message-----
From: Douglas Bagnall <douglas.bagnall at catalyst.net.nz>
Sent: Tuesday, December 23, 2025 3:40 PM
To: Interoperability Documentation Help <dochelp at microsoft.com>; cifs-protocol at lists.samba.org
Subject: [EXTERNAL] is MS-DRSR 4.1.10.5.21 CompressOrDecompressWin2k3 the same as MS-WUSP 2.1.1.1 CompressOrDecompressWin2k3 ?

hi Dochelp.

The MS-DRSR and MS-WUSP definitions of CompressOrDecompressWin2k3 look very similar.
Are they really the same procedure?

If they are in fact the same, my next question is which document is most correct.
I haven't looked closely, but I see these differences:

MS-WUSP: This scheme is good for lengths of up to 279
MS-DRSR: This scheme is good for lengths of up to 278

MS-WUSP: a match length of up to 65,535 bytes + 3 bytes
MS-DRSR: a match length of up to 32,768 bytes + 3 bytes

Perhaps one has been updated and not the other?


In November 2022[1] I asked if MS-XCA 2.3 and 2.4 "Plain LZ77" was the same as the MS-DRSR procedure. The answer was "MS-DRSR uses a different API than what MS-XCA uses", which I took to mean that even if it was initially intended that they were the same, they could easily be accidentally different. I guess my first question could be answered in the same way -- are these using the same shared library function?

[1] https://lists.samba.org/archive/cifs-protocol/2022-November/003902.html

cheers,
Douglas