[cifs-protocol] [EXTERNAL] Is MS-XCA LZ-77 plain compression the same as MS-DRSR DRS_COMP_ALG_WIN2K3 compression? - TrackingID#2211280040006230

[Andrew Bartlett]

Kia Ora Douglas,
(moved to samba-technical)
Thanks for asking this and getting a definitive answer. 
You know this, but just to make a note: we should probably update the
comment in lzxpress_compress() to link to 
https://lists.samba.org/archive/cifs-protocol/2022-December/003914.html
 and point at the correct specification. 
Andrew,
On Sat, 2022-12-03 at 13:36 +1300, Douglas Bagnall via cifs-protocol
wrote:
> hi Obaid,
> Yes, that answers the question, at least to "easy to answer"
> threshold.
> It looks to me like they may once have been intended to be the same
> but have diverged, which doesn't matter in practice because they
> don't talk to each other. I don't need to know any more than this
> now.
> thank you,Douglas
> 
> On 3/12/22 13:10, Obaid Farooqi wrote:
> > Hi Douglas:The MS-DRSR uses a different API than what MS-XCA uses.
> > Please let me know if this does not answer your question.
> > Regards,Obaid FarooqiEscalation Engineer | Microsoft
> > -----Original Message-----From: Tom Jebo <tomjebo at microsoft.com>Sen
> > t: Monday, November 28, 2022 11:02 AMTo: Douglas Bagnall <
> > douglas.bagnall at catalyst.net.nz>; cifs-protocol at lists.samba.org
> > Cc: Microsoft Support <supportmail at microsoft.com>Subject: RE:
> > [EXTERNAL] Is MS-XCA LZ-77 plain compression the same as MS-DRSR
> > DRS_COMP_ALG_WIN2K3 compression? - TrackingID#2211280040006230
> > [dochelp to bcc][support mail to cc]
> > Hi Douglas,
> > Thanks for you request regarding MS-XCA. One of the Open
> > Specifications team members will respond to assist you. In the
> > meantime, we’ve created case 2211280040006230 to track this
> > request. Please leave the case number in the subject when
> > communicating with our team about this request.
> > Best regards,Tom JeboMicrosoft Open Specifications Support
> > -----Original Message-----From: Douglas Bagnall <
> > douglas.bagnall at catalyst.net.nz>Sent: Sunday, November 27, 2022
> > 7:30 PMTo: Interoperability Documentation Help <
> > dochelp at microsoft.com>; cifs-protocol at lists.samba.org
> > Subject: [EXTERNAL] Is MS-XCA LZ-77 plain compression the same as
> > MS-DRSR DRS_COMP_ALG_WIN2K3 compression?
> > hi Dochelp,
> > Hopefully this will be simple to answer.
> > The algorithm in MS-XCA 2.3 and 2.4 "Plain LZ77" looks quite a lot
> > like the one in MS-DRSR 4.1.10.5.21 "CompressOrDecompressWin2k3" or
> > "LZ77 + DIRECT2", although they are described using entirely
> > different words.
> > (MS-WUSP and MS-OXCRPC also have something similar).
> > If this is *not* easy to answer, I am happy to accept a "maybe". At
> > this stage I am just curious.
> > cheers,Douglas
> 
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-- 
Andrew Bartlett (he/him)       https://samba.org/~abartlet/Samba Team Member (since 2001) https://samba.orgSamba Team Lead, Catalyst IT   https://catalyst.net.nz/services/samba
Samba Development and Support, Catalyst IT - Expert Open SourceSolutions