Is it possible to get a copy of the FSDiffStream protocol specification?

Question

Is it possible to get a copy of the FSDiffStream protocol specification?

John A 0

We would like to gain a deeper understanding of the FSDiffStream protocol to describe elements of the protocol that we need to pass through a Cross Domain Solution and therefore at least syntactically validate. Is there a spec anywhere?

Sreekanth Nadendla 491 Reputation points Microsoft Employee Moderator

2025-04-26T16:15:34.6733333+00:00

Hello John, can you provide some details about what FSDiffStream is about? Is it for accessing distributed file system? Perhaps what you are looking for is titled under a different name, so it would be helpful to know some context here.

Regards,

Sreekanth Nadendla

Windows Open Specifications
John A 0 Reputation points

2025-04-28T16:40:40.56+00:00

Hi Sreekanth. We believe it is the data format used by MS-FSSHTTP to support collaborative editing of a Word document. Once a document is selected by two users in SharePoint, the collaborative edit session is handed-off to the Office Online Server (OOS). FSDiffStream is used in the payloads of messages between the OOS and the webclients. It records the micro-changes to the Word document as the two users collaboratively change the document. This is all self-managed on-premise. It's the equivalent of the Fluid Framework, which we believe is used for the 365 SaaS offering.
Tom Jebo 2,161 Reputation points Microsoft Employee Moderator

2025-04-28T23:52:46.9066667+00:00

Hey John A,

I'll look into this for you. I'm not familiar with FSDiffStream. Are you attempting to use ExecuteCellStorageRequest in WOPI traffic? All of the data formatting, chunking and graphing type operations used by FSSHTTP protocol should be described in the existing MS-FSSHTTP, MS-FSSHTTPB and MS-FSSHTTPD documents.

Specifically the B document contains the binary structures and graph organization for the incremental updating of documents across the wire.

And the D document contains information about what Sharepoint uses when dealing with zip files, binary and any other file formats to chunk the documents into partitions and cells based on the "change profile" (i.e. which parts of a file format are likely to change). MS-FSSHTTPD 1.3.1 has a brief description this "schema" and perhaps maps to what you're referring?

If you can tell me more about where you found that name and/or what exactly you're trying to accomplish, maybe I can figure out where to look for the specifications.

Best regards,
Tom Jebo
Microsoft Open Specifications Support
John A 0 Reputation points

2025-04-29T10:25:43.3166667+00:00

Hi Tom. Thanks for the above links.

We have an on-premise SharePoint/OOS server that is used by local clients for real-time collaboration (e.g., co-editing a Word document), and we'd like to allow remote users to do the same. From a security perspective, we must tunnel the remote user traffic through a Cross Domain Solution (CDS). Part of the job of the CDS is to validate the traffic flowing through it. We therefore need to gain a deep understanding of the protocols/data formats in play, to be able to describe this traffic (ultimately using an XML schema). We believe the MS-FSSHTTP protocol is being used to transport FSDiffStream payloads. Here's part of an co-edit session:

"RevisionList": [ { "BaseId": "00000000-0000-0000-0000-000000000000|0", "ObjectGroups": [ { "Id": "1262889f-4973-42c6-a8b3-b2da01dc0306|1", "Objects": [ { "ClassId": 393220, "ObjectId": "6ddad14f-1b38-457a-9b58-0f0f4ea94224|4", "Properties": [ 603986976, "{6ddad14f-1b38-457a-9b58-0f0f4ea94224}{3}" ] }, { "ClassId": 393221, "ObjectId": "6ddad14f-1b38-457a-9b58-0f0f4ea94224|3", "Properties": [ 469770255, "WOPIsrc=http%3A%2F%2Fec2amaz%2Dqgp8849%2Fsites%2Ftest1%2F%5Fvti%5Fbin%2Fwopi%2Eashx%2Ffiles%2Ffd3a4ea9d16d4bdebc33d164fbc93f93&access_token=eyJ0eXAiOiJKV1QiLCJhbGciOiJSUzI1NiIsIng1dCI6IkpRdTIzRFhNcy1VN3Y4Ym1tUHoxNGFzZFZnbyJ9%2EeyJuYW1laWQiOiIwIy53fHNoYXJlcG9pbnQtdGVzdFxcc3BvcmcydXNlcjEiLCJuaWkiOiJtaWNyb3NvZnQuc2hhcmVwb2ludCIsImlzdXNlciI6InRydWUiLCJjYWNoZWtleSI6IjApLnd8cy0xLTUtMjEtMjEyMzU2MjMyNC0xNjgxNjQxODIyLTMyMTQ2MjQ5NjYtMTEyNSIsImlzcyI6IjAwMDAwMDAzLTAwMDAtMGZmMS1jZTAwLTAwMDAwMDAwMDAwMEA2ZjBiY2RmMS1mNDFlLTRiNDEtODU4Ni1jNjAyZjk2NmM4ZTAiLCJhdWQiOiJ3b3BpL2VjMmFtYXotcWdwODg0OUA2ZjBiY2RmMS1mNDFlLTRiNDEtODU4Ni1jNjAyZjk2NmM4ZTAiLCJleHAiOjE3NDU0MTE1MzYsIm5iZiI6MTc0NTM3NTUzNiwiaXNsb29wYmFjayI6IlRydWUiLCJhcHBjdHgiOiJmZDNhNGVhOWQxNmQ0YmRlYmMzM2QxNjRmYmM5M2Y5MzsvOTJFTGhQZFAzRDRscG1mak8vK29CeXdoYzQ9O0RlZmF1bHQ7OzdGRkZGRkZGRkZGRkZGRkY7VHJ1ZTsifQ%2EZqBXfLabUt6JcdX%5F99NlfTRkGRBuetYq0PL1gFJjhGVO3xlFmgLVE1u1z3TA2GEu1CbIG7edX4jHRE6omoN5nCitWkuUxsve8Z5wU6s4CErg1wMX67azX91xrxka%2DJSuWzLcY8BjH8HeI5Gb96M7g17YK6%5F7yoPbVYG%2DsFDqnW%2Dy2JwqYM81DVElwxn40bt9ebrH%5FYOqNMO33rWhUAuKnu4zIeearQgjhg5dmnXCmWo1v2NLqZ3jmAiKSmLWAaxBW3LW1vP371XAMnggAdXuyS1uWefk6xSp3awbtoGWJDG32bPvqyV%5FVc%2DupRkvk%2DDjwSnbqX91dViy8FZYpPiMkg&access_token_ttl=1745411536947", 469770293, "http%3A%2F%2Fec2amaz%2Dqgp8849%2Fsites%2Ftest1%2F%5Fvti%5Fbin%2Fwopi%2Eashx%2Ffiles%2Ffd3a4ea9d16d4bdebc33d164fbc93f93" ] } ] } ]

We're trying to model the above as a schema, which we can do by capturing the above and working through each field, but we were hoping the payloads might be described (reference the field names in their JSON format) in an open spec somewhere? Would a call be possible - in a short call I can probably explain this more efficiently.

John
Tom Jebo 2,161 Reputation points Microsoft Employee Moderator

2025-04-30T18:07:26.41+00:00

Hey John A,

Thanks for the explanation. I am getting an idea of what you're doing but perhaps we can call as you suggested. Can you email me at dochelp@microsoft.com so that I can arrange to meet with you? Please include the URL for this forum thread in your email.

Tom
John A 0 Reputation points

2025-05-01T09:48:41.66+00:00

Thanks Tom. Email sent.

Your answer

Sreekanth Nadendla 491 Reputation points Microsoft Employee Moderator

2025-04-26T16:15:34.6733333+00:00

Hello John, can you provide some details about what FSDiffStream is about? Is it for accessing distributed file system? Perhaps what you are looking for is titled under a different name, so it would be helpful to know some context here.

Regards,

Sreekanth Nadendla

Windows Open Specifications
John A 0 Reputation points

2025-04-28T16:40:40.56+00:00

Hi Sreekanth. We believe it is the data format used by MS-FSSHTTP to support collaborative editing of a Word document. Once a document is selected by two users in SharePoint, the collaborative edit session is handed-off to the Office Online Server (OOS). FSDiffStream is used in the payloads of messages between the OOS and the webclients. It records the micro-changes to the Word document as the two users collaboratively change the document. This is all self-managed on-premise. It's the equivalent of the Fluid Framework, which we believe is used for the 365 SaaS offering.
Tom Jebo 2,161 Reputation points Microsoft Employee Moderator

2025-04-28T23:52:46.9066667+00:00

Hey John A,

I'll look into this for you. I'm not familiar with FSDiffStream. Are you attempting to use ExecuteCellStorageRequest in WOPI traffic? All of the data formatting, chunking and graphing type operations used by FSSHTTP protocol should be described in the existing MS-FSSHTTP, MS-FSSHTTPB and MS-FSSHTTPD documents.

Specifically the B document contains the binary structures and graph organization for the incremental updating of documents across the wire.

And the D document contains information about what Sharepoint uses when dealing with zip files, binary and any other file formats to chunk the documents into partitions and cells based on the "change profile" (i.e. which parts of a file format are likely to change). MS-FSSHTTPD 1.3.1 has a brief description this "schema" and perhaps maps to what you're referring?

If you can tell me more about where you found that name and/or what exactly you're trying to accomplish, maybe I can figure out where to look for the specifications.

Best regards,
Tom Jebo
Microsoft Open Specifications Support
Tom Jebo 2,161 Reputation points Microsoft Employee Moderator

2025-04-30T18:07:26.41+00:00

Hey John A,

Thanks for the explanation. I am getting an idea of what you're doing but perhaps we can call as you suggested. Can you email me at dochelp@microsoft.com so that I can arrange to meet with you? Please include the URL for this forum thread in your email.

Tom
John A 0 Reputation points

2025-05-01T09:48:41.66+00:00

Thanks Tom. Email sent.

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Is it possible to get a copy of the FSDiffStream protocol specification?

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