Retried Packets when exceeding 700 Mbits

[mouthpiec]

Hi,
Currently I am testing throughput capabilities of the 6850 switches using iPerf.
The setup consists of the following:

iPerf Server1 --> 6850 L2 switch --> Cisco L2 switch --> iPerf Server2 (all interfaces are 1Gbps)

It was noted that when pushing traffic from Server2 to Server1 (Cisco--> 6850) there are Retried packets and throughput of 940Mbps is reached.
When pushing traffic the other way round, when exceeding 650Mbps there are packets Retries and this value increase when throughput is increased.

The servers were connected back to back and no loss was reported.

Are you aware of any throughput limitation on the Omniswitches?


Example of iPerf results below:

700Mbps test - 385 retried packets

Code: Select all

root@# iperf3 -c 80.254.87.2 -b 700M
Connecting to host 80.254.87.2, port 5201
[  4] local 217.22.189.203 port 50886 connected to 80.254.87.2 port 5201
[ ID] Interval           Transfer     Bandwidth       Retr  Cwnd
[  4]   0.00-1.00   sec  82.7 MBytes   693 Mbits/sec   56    329 KBytes       
[  4]   1.00-2.00   sec  76.0 MBytes   637 Mbits/sec   28    386 KBytes       
[  4]   2.00-3.00   sec  89.2 MBytes   749 Mbits/sec   27    382 KBytes       
[  4]   3.00-4.00   sec  85.4 MBytes   716 Mbits/sec   55    354 KBytes       
[  4]   4.00-5.00   sec  80.8 MBytes   677 Mbits/sec   28    358 KBytes       
[  4]   5.00-6.00   sec  78.4 MBytes   657 Mbits/sec    0    411 KBytes       
[  4]   6.00-7.00   sec  83.8 MBytes   703 Mbits/sec   55    277 KBytes       
[  4]   7.00-8.00   sec  89.9 MBytes   754 Mbits/sec   54    276 KBytes       
[  4]   8.00-9.00   sec  81.4 MBytes   683 Mbits/sec   54    255 KBytes       
[  4]   9.00-10.00  sec  86.2 MBytes   724 Mbits/sec   28    385 KBytes       
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bandwidth       Retr
[  4]   0.00-10.00  sec   834 MBytes   699 Mbits/sec  385             sender
[  4]   0.00-10.00  sec   832 MBytes   698 Mbits/sec                  receiver

650Mbps test - no retries

Code: Select all

root@# iperf3 -c 80.254.87.2 -b 650M
Connecting to host 80.254.87.2, port 5201
[  4] local 217.22.189.203 port 50890 connected to 80.254.87.2 port 5201
[ ID] Interval           Transfer     Bandwidth       Retr  Cwnd
[  4]   0.00-1.00   sec  74.9 MBytes   628 Mbits/sec    0    482 KBytes       
[  4]   1.00-2.00   sec  78.6 MBytes   660 Mbits/sec    0    482 KBytes       
[  4]   2.00-3.00   sec  71.2 MBytes   598 Mbits/sec    0    482 KBytes       
[  4]   3.00-4.00   sec  79.0 MBytes   663 Mbits/sec    0    505 KBytes       
[  4]   4.00-5.00   sec  80.8 MBytes   677 Mbits/sec    0    529 KBytes       
[  4]   5.00-6.00   sec  79.4 MBytes   666 Mbits/sec    0    529 KBytes       
[  4]   6.00-7.00   sec  73.9 MBytes   620 Mbits/sec    0    556 KBytes       
[  4]   7.00-8.00   sec  76.2 MBytes   640 Mbits/sec    0    585 KBytes       
[  4]   8.00-9.00   sec  79.9 MBytes   670 Mbits/sec    0    612 KBytes       
[  4]   9.00-10.00  sec  77.2 MBytes   648 Mbits/sec    0    642 KBytes       
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bandwidth       Retr
[  4]   0.00-10.00  sec   771 MBytes   647 Mbits/sec    0             sender
[  4]   0.00-10.00  sec   771 MBytes   647 Mbits/sec                  receiver

[devnull]

From my knowledge all (current) switches are wirespeed, so there should not be a issue.

Switching Servers (Server 2 to Cisco, Server 1 to 6850) moves the problem (so problem is always when sending from OS6850 connected device?)
If you can push from S1 (Cisco) to S2 (OS6850) with 940MBit, then there is no general forwarding issue, as here the OS6850 is involved as well..
i wonder why a switch should behave different regarding the direction

[mouthpiec]

From my knowledge all (current) switches are wirespeed, so there should not be a issue.

Switching Servers (Server 2 to Cisco, Server 1 to 6850) moves the problem (so problem is always when sending from OS6850 connected device?)
If you can push from S1 (Cisco) to S2 (OS6850) with 940MBit, then there is no general forwarding issue, as here the OS6850 is involved as well..
i wonder why a switch should behave different regarding the direction

Hi devnull ... thanks for your reply.
Today we tried further tests were we connected the iperf servers between two 6850 switches.
It was noted that issue occurs only when the vlan between the switches is 802.1q. When it is assigned as Access port, no issues are encountered

[devnull]

Open a ticket woth TAC-
I have no idea.