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tcp window and SMB v3 multi session

Dear all,

I am troubleshooting SMB v3 throughput performance issue. Currently, I saw the TCP window scaling flag is -1, I understand that's because Wireshark did not see TCP handshake to know the scaling status, but I turn on Wireshark before setup \x.x.x.x file server link to SMB server but still did not get this flag status.

I would like to know does anyone have suggestions for the following questions: (The server uses NAS and do not have access right to check the server status)

  1. how to calculate the TCP window size in client and server-side under the flag is -1 situation?
  2. Have a command to check current TCP windows in windows 10 directly? I do not have access right in the server-side.
  3. I found SMB supports multi-stream (not multi-channel for dual interface), but it seems sometimes the client can't run multi-stream always. Does anyone have a similar experience to this? The client ConnectionCountPerRssNetworkInterface is 4. I read the Micorosft document that mentioned multi-session can only work under a virtual interface. is it true?
  4. Any ideas to improve SMB v3 file transfer throughput on Windows 10 side?

Thank you very much! codec