Description of problem:
When data is downloaded from external source to the VM, throughput is extremely low  (~1-5Mbps) to a point where it leaves the user wondering if the environment is even functional. However, when the VM is sending the traffic, the throughput seems fine(~500Mbps). These results were obtained using the iperf tests, with egress throughput  being traffic sent from VM to external source and ingress being Vica-versa. The external source was setup to be within Red Hat and also a public iperf server was tried. In both cases, no differences in throughput were observed. The VM had a floating ip, and even without a floating ip we were seeing similar bad performance in N-S traffic download case.

Version-Release number of selected component (if applicable):


How reproducible:
100%

Steps to Reproduce:
1. Create network, subnet, router and VM
2. Attach router to external
3. Setup external iperf3 server and run iperf tests with the VM being the client

Actual results:
Throughput of iperf ingress case was around 5Mbps. Some cases it was less than 1 Mbps

Expected results:
Throughput similar to TCP Upload case ~500 Mbps


Additional info:
TCP Download results: http://8.43.86.1:8088/smalleni/sai-tcpoff.html#agent=shaker_tioepm_agent_0:concurrency=1:node=overcloud-novacompute-0.localdomain:scenario=OpenStack%20L3%20North-South%20performance%20to%20external%20target%20with%20floating%20IP:test=TCP%20ingress


TCp upload results: http://8.43.86.1:8088/smalleni/sai-tcpoff.html#agent=shaker_tioepm_agent_0:concurrency=1:node=overcloud-novacompute-0.localdomain:scenario=OpenStack%20L3%20North-South%20performance%20to%20external%20target%20with%20floating%20IP:test=TCP%20egress