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what determines the final windows scaling factor?

what determines the final windows scaling factor? example FTP client initiates a TCP connection and has a 1GIG interface. Window scaling is enabled.

RTT is 76ms

in the original SYN packet it had: MSS is 1460. window size value: 65535,

window scale: 7 (multiply by 128).

SYN-ACK from opposite side: MSS is 1260, window size value: 8192,

window scale: 14 (multiply by 16384).

in final ACK it came to: Window size value: 32768, window size scaling factor: 128, calculated window size: 4194304.

(for the rest of FTP transfer it stayed on this value: 4194304)

so 2 questions regarding initiating side (FTP client): 1)How at the end the window size reduced to 32768 on the initiating side? 2) Why if the interface is set to GIG - it did not use the 14 as window scale ? but used 7?what could have determined that - is it a hard setting on server or did the TCP connection catch some buffer on the network? thanks for any help Nik

what determines the final windows scaling factor?

what determines the final windows scaling factor? example FTP client initiates a TCP connection and has a 1GIG interface. Window scaling is enabled.

RTT is 76ms

in the original SYN packet it had: MSS is 1460. window size value: 65535,

window scale: 7 (multiply by 128).

SYN-ACK from opposite side: MSS is 1260, window size value: 8192,

window scale: 14 (multiply by 16384).

in final ACK it came to: Window size value: 32768, window size scaling factor: 128, calculated window size: 4194304.

(for the rest of FTP transfer it stayed on this value: 4194304)

trace:

https://www.dropbox.com/s/kx6dyt9bf3p4jtv/SLC%20on%201G%2011-9-2017%201024_anon.pcapng?dl=0

so 2 questions regarding initiating side (FTP client): 1)How at the end the window size reduced to 32768 on the initiating side? 2) Why if the interface is set to GIG - it did not use the 14 as window scale ? but used 7?what could have determined that - is it a hard setting on server or did the TCP connection catch some buffer on the network? thanks for any help Nik

what determines the final windows scaling factor?

what determines the final windows scaling factor? example FTP client initiates a TCP connection and has a 1GIG interface. Window scaling is enabled.

enabled. RTT is 76ms

in the original SYN packet it had:

MSS is 1460. 
window size value: 65535,  

window scale: 7 (multiply by 128).

128).

SYN-ACK from opposite side:

MSS is 1260, 
window size value: 8192,  

window scale: 14 (multiply by 16384).

16384).

in final ACK it came to:

Window size value: 32768,
 window size scaling factor: 128,
 calculated window size: 4194304.

4194304.

(for the rest of FTP transfer it stayed on this value: 4194304)

trace:

trace: https://www.dropbox.com/s/kx6dyt9bf3p4jtv/SLC%20on%201G%2011-9-2017%201024_anon.pcapng?dl=0

so 2 questions regarding initiating side (FTP client): 1)How client):

  1. How at the end the window size reduced to 32768 on the initiating side? 2)
  2. Why if the interface is set to GIG - it did not use the 14 as window scale ? but used 7?what could have determined that - is it a hard setting on server or did the TCP connection catch some buffer on the network? network?

thanks for any help Nik