iperfテスト帯域幅の問題--上下行帯域幅の差が大きい

今日、マシンルームの2台のサーバ間のネットワーク帯域幅をテストし、奇妙な現象を発見しました.
同時に、上下帯域幅をテストします.

[root@ptl3m log]# iperf -c 172.28.2.21 -t 60 -i 10  -d -L 8083
------------------------------------------------------------
Server listening on TCP port 8083
TCP window size: 4.00 KByte (default)
------------------------------------------------------------
------------------------------------------------------------
Client connecting to 172.28.2.21, TCP port 5001
TCP window size:  400 KByte (default)
------------------------------------------------------------
[  3] local 172.28.2.23 port 46174 connected with 172.28.2.21 port 5001
[  5] local 172.28.2.23 port 8083 connected with 172.28.2.21 port 39939
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0-10.0 sec  4.37 GBytes  3.75 Gbits/sec
[  5]  0.0-10.0 sec   552 MBytes   463 Mbits/sec
[  3] 10.0-20.0 sec  4.84 GBytes  4.16 Gbits/sec
[  5] 10.0-20.0 sec   221 MBytes   185 Mbits/sec
[  3] 20.0-30.0 sec  4.87 GBytes  4.19 Gbits/sec
[  5] 20.0-30.0 sec   303 MBytes   254 Mbits/sec
[  3] 30.0-40.0 sec  4.01 GBytes  3.45 Gbits/sec
[  5] 30.0-40.0 sec  1.04 GBytes   891 Mbits/sec
[  3] 40.0-50.0 sec  4.81 GBytes  4.14 Gbits/sec
[  5] 40.0-50.0 sec   223 MBytes   187 Mbits/sec
[  3] 50.0-60.0 sec  4.75 GBytes  4.08 Gbits/sec
[  3]  0.0-60.0 sec  27.7 GBytes  3.96 Gbits/sec
[  5] 50.0-60.0 sec   347 MBytes   291 Mbits/sec
[  5]  0.0-60.0 sec  2.65 GBytes   379 Mbits/sec

以上から,この試験方法は上下帯域幅の差が大きいことが分かった.しかし、次のコマンドテストを使用すると、帯域幅の差はそれほど大きくありません.

[root@ptl3m log]# iperf -c 172.28.2.21 -t 60 -i 10  -r -L 8083
------------------------------------------------------------
Server listening on TCP port 8083
TCP window size: 4.00 KByte (default)
------------------------------------------------------------
------------------------------------------------------------
Client connecting to 172.28.2.21, TCP port 5001
TCP window size:  400 KByte (default)
------------------------------------------------------------
[  3] local 172.28.2.23 port 46130 connected with 172.28.2.21 port 5001
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0-10.0 sec  4.67 GBytes  4.01 Gbits/sec
[  3] 10.0-20.0 sec  4.17 GBytes  3.58 Gbits/sec
[  3] 20.0-30.0 sec  4.70 GBytes  4.04 Gbits/sec
[  3] 30.0-40.0 sec  4.92 GBytes  4.23 Gbits/sec
[  3] 40.0-50.0 sec  4.86 GBytes  4.18 Gbits/sec
[  3] 50.0-60.0 sec  4.28 GBytes  3.68 Gbits/sec
[  3]  0.0-60.0 sec  27.6 GBytes  3.95 Gbits/sec
[  5] local 172.28.2.23 port 8083 connected with 172.28.2.21 port 38653
[  5]  0.0-10.0 sec  3.91 GBytes  3.36 Gbits/sec
[  5] 10.0-20.0 sec  4.02 GBytes  3.45 Gbits/sec
[  5] 20.0-30.0 sec  3.92 GBytes  3.37 Gbits/sec
[  5] 30.0-40.0 sec  4.02 GBytes  3.45 Gbits/sec
[  5] 40.0-50.0 sec  4.06 GBytes  3.49 Gbits/sec
[  5]  0.0-60.0 sec  24.1 GBytes  3.44 Gbits/sec

この−dおよび−rパラメータは結果に影響を及ぼしたのか,それともNICのフルデュプレクスに問題があったのか,それとも他の構成に問題があったのか.ご指導をお願いします.ありがとう