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BDP and TCP window size: Why file copy between sql server is slow (5MByte/sec)

 I have 700GB sql server database dump file need to be copied from prod server to test, the copy speed is only 5MByte/s,  I asked network admin, here is his response:

"

Based on a queue depth of approximately 20% of our 1Gbps WAN link and a latency of 12ms between Data Centers the speed you're receiving is in alignment with a standard TCP Window of 64KB.

 BDP (200 Mbit/sec, 12.0 ms) = 0.30 MByte

required tcp buffer to reach 200 Mbps with RTT of 12.0 ms >= 293.0 KByte
maximum throughput with a TCP window of 64 KByte and RTT of 12.0 ms <= 43.69 Mbit/sec.

 == 5.46125 MB/s

"

To understand it better, this link explain what BDP is:

https://youtu.be/vPCKWhXSAEo

This link below explain how BDP and tcp receiver buffer works:

http://ce.sc.edu/cyberinfra/workshops/Material/perfSONAR/Lab%206.pdf

Then lead to the solution how to change it, described here: 

https://learn.microsoft.com/en-us/troubleshoot/windows-server/networking/description-tcp-features


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