1 | initial version |

Hi, refer to this quite detailed article

So assuming you have Windows OS it chooses Scale factor based on 2 factors: interface speed and selected Received Window autotuning level:

"...So, as summary, the different states for AutoTuningLevel are as follows:

Normal (Default): 0x8 (Scale Factor of 8)

Restricted: 0x4 (Scale Factor of 4)

Highly Restricted: 0x2 (Scale Factor of 2)

Disable: No scale factor available

Experimental: 0xE (Scale Factor of 14)..."

Later, after connection is established, Windows OS uses current receive rate to update RWIN size accourdingly (unlike Scaling factor which is set in SYN packets, we can change RWIN size all the time connection is active).

2 | No.2 Revision |

Hi, refer to this quite detailed article

So assuming you have Windows OS it chooses Scale factor based on 2 factors: interface speed and selected Received Window autotuning level:

"...So, as summary, the different states for AutoTuningLevel are as follows:

Normal (Default): 0x8 (Scale Factor of 8)

Restricted: 0x4 (Scale Factor of 4)

Highly Restricted: 0x2 (Scale Factor of 2)

Disable: No scale factor available

Experimental: 0xE (Scale Factor of 14)..."

Later, after connection is established, Windows OS uses current receive rate to update RWIN size accourdingly (unlike Scaling factor which is set in SYN packets, we can change RWIN size all the time connection is active).

I've just checked my Win 10 with 'Normal' autotuning level and indeed it shooses Scalinf Factor of 8 in every TCP connection.

3 | No.3 Revision |

Hi, refer to this quite detailed article

So assuming you have Windows OS it chooses Scale ~~factor ~~Factor based on 2 factors: interface speed and selected Received Window autotuning level:

"...So, as summary, the different states for AutoTuningLevel are as follows:

Normal (Default): 0x8 (Scale Factor of 8)

Restricted: 0x4 (Scale Factor of 4)

Highly Restricted: 0x2 (Scale Factor of 2)

Disable: No scale factor available

Experimental: 0xE (Scale Factor of 14)..."

Later, after connection is established, Windows OS uses current receive rate to update RWIN size accourdingly (unlike Scaling factor which is set in SYN packets, we can change RWIN size all the time connection is active).

I've just checked my Win 10 with 'Normal' autotuning level and indeed it shooses ~~Scalinf ~~Scale Factor of 8 in every TCP connection.

4 | No.4 Revision |

Hi, refer to this quite detailed article

So assuming you have Windows OS it ~~chooses Scale Factor ~~control RWIN size based on 2 factors: interface speed and selected Received Window autotuning level:

"...So, as summary, the different states for AutoTuningLevel are as follows:

Normal (Default): 0x8 (Scale Factor of 8)

Restricted: 0x4 (Scale Factor of 4)

Highly Restricted: 0x2 (Scale Factor of 2)

Disable: No scale factor available

Experimental: 0xE (Scale Factor of 14)..."

I've just checked my Win 10 with 'Normal' autotuning level and indeed it shooses Scale Factor of 8 in every TCP connection.

5 | No.5 Revision |

Hi, refer to this quite detailed article

So assuming you have Windows OS it ~~control ~~controls RWIN size based on 2 factors: interface speed and selected Received Window autotuning level:

"...So, as summary, the different states for AutoTuningLevel are as follows:

Normal (Default): 0x8 (Scale Factor of 8)

Restricted: 0x4 (Scale Factor of 4)

Highly Restricted: 0x2 (Scale Factor of 2)

Disable: No scale factor available

Experimental: 0xE (Scale Factor of 14)..."

I've just checked my Win 10 with 'Normal' autotuning level and indeed it shooses Scale Factor of 8 in every TCP connection.

6 | No.6 Revision |

Hi, refer to this quite detailed article

So assuming you have Windows OS it controls RWIN size based on 2 factors: interface speed and selected ~~Received ~~Receiving Window autotuning level:

"...So, as summary, the different states for AutoTuningLevel are as follows:

Normal (Default): 0x8 (Scale Factor of 8)

Restricted: 0x4 (Scale Factor of 4)

Highly Restricted: 0x2 (Scale Factor of 2)

Disable: No scale factor available

Experimental: 0xE (Scale Factor of 14)..."

I've just checked my Win 10 with 'Normal' autotuning level and indeed it shooses Scale Factor of 8 in every TCP connection.

7 | No.7 Revision |

Hi, refer to this quite detailed article

So assuming you have Windows OS it controls RWIN size based on 2 factors: interface speed and selected ~~Receiving ~~Receive Window autotuning level:

"...So, as summary, the different states for AutoTuningLevel are as follows:

Normal (Default): 0x8 (Scale Factor of 8)

Restricted: 0x4 (Scale Factor of 4)

Highly Restricted: 0x2 (Scale Factor of 2)

Disable: No scale factor available

Experimental: 0xE (Scale Factor of 14)..."

8 | No.8 Revision |

Hi, refer to this quite detailed article

So assuming you have Windows OS it controls RWIN size based on 2 factors: interface speed and selected Receive Window autotuning level:

"...So, as summary, the different states for AutoTuningLevel are as follows:

Normal (Default): 0x8 (Scale Factor of 8)

Restricted: 0x4 (Scale Factor of 4)

Highly Restricted: 0x2 (Scale Factor of 2)

Disable: No scale factor available

Experimental: 0xE (Scale Factor of 14)..."

Also as Jim said before it'd be nice to see PCAP and check if it is exactly the reason of low throughput.

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