iPerf3测试2.5G链路时正向与反向速率不一致问题求助

各位好，最近我给主力Windows 10台式机和Ubuntu 20.04 NAS服务器都换上了2.5GB网卡，但测试时遇到了一个奇怪的问题，想请大家帮忙分析下：

当我从Windows端发起iPerf3测试（数据从Windows传到Ubuntu），速率只能跑到1GB左右；但使用--reverse参数让数据从Ubuntu传到Windows时，就能跑到接近2.5GB的正常速率。

更奇怪的是，不管iPerf3的服务端（用-s参数启动）是在Ubuntu还是Windows机器上，这个现象都一致。我还特意换了两根不同的网线测试，结果还是一样。

下面是具体的测试数据：

服务器在Ubuntu，数据从Windows传到Ubuntu的测试结果 #

H:\Downloads\iperf-3.1.3-win64

λ iperf3 -c 10.0.51.3

Connecting to host 10.0.51.3, port 5201

[  4] local 10.0.51.2 port 1111 connected to 10.0.51.3 port 5201

[ ID] Interval           Transfer     Bandwidth

[  4]   0.00-1.00   sec   120 MBytes  1.01 Gbits/sec

[  4]   1.00-2.00   sec   120 MBytes  1.01 Gbits/sec

[  4]   2.00-3.00   sec   120 MBytes  1.00 Gbits/sec

[  4]   3.00-4.00   sec   118 MBytes   994 Mbits/sec

[  4]   4.00-5.00   sec   119 MBytes   994 Mbits/sec

[  4]   5.00-6.00   sec   120 MBytes  1.00 Gbits/sec

[  4]   6.00-7.00   sec   118 MBytes   992 Mbits/sec

[  4]   7.00-8.00   sec   117 MBytes   984 Mbits/sec

[  4]   8.00-9.00   sec   119 MBytes   999 Mbits/sec

[  4]   9.00-10.00  sec   117 MBytes   984 Mbits/sec

- - - - - - - - - - - - - - - - - - - - - - - - -

[ ID] Interval           Transfer     Bandwidth

[  4]   0.00-10.00  sec  1.16 GBytes   997 Mbits/sec                  sender

[  4]   0.00-10.00  sec  1.16 GBytes   997 Mbits/sec                  receiver

iperf Done.

反向测试：数据从Ubuntu传到Windows的结果 #

H:\Downloads\iperf-3.1.3-win64

λ iperf3 -c 10.0.51.3 --reverse

Connecting to host 10.0.51.3, port 5201

Reverse mode, remote host 10.0.51.3 is sending

[  4] local 10.0.51.2 port 1122 connected to 10.0.51.3 port 5201

[ ID] Interval           Transfer     Bandwidth

[  4]   0.00-1.00   sec   273 MBytes  2.29 Gbits/sec

[  4]   1.00-2.00   sec   272 MBytes  2.28 Gbits/sec

[  4]   2.00-3.00   sec   276 MBytes  2.31 Gbits/sec

[  4]   3.00-4.00   sec   273 MBytes  2.29 Gbits/sec

[  4]   4.00-5.00   sec   274 MBytes  2.30 Gbits/sec

[  4]   5.00-6.00   sec   272 MBytes  2.29 Gbits/sec

[  4]   6.00-7.00   sec   275 MBytes  2.30 Gbits/sec

[  4]   7.00-8.00   sec   274 MBytes  2.30 Gbits/sec

[  4]   8.00-9.00   sec   276 MBytes  2.32 Gbits/sec

[  4]   9.00-10.00  sec   275 MBytes  2.30 Gbits/sec

- - - - - - - - - - - - - - - - - - - - - - - - -

[ ID] Interval           Transfer     Bandwidth       Retr

[  4]   0.00-10.00  sec  2.68 GBytes  2.30 Gbits/sec    0             sender

[  4]   0.00-10.00  sec  2.68 GBytes  2.30 Gbits/sec                  receiver

iperf Done.

备注：内容来源于stack exchange，提问作者EngageBasic