Hi Erik,

Thx for picking up my questions…

We’re using OCP v3.1 and the openshift-sdn.

Both IP and DNS name of containers are used in the tests.

If it can help, I can include more detailed test results in various scenarios.

Do you think a newer version of ocp will improve on this ? thx !

Kind regards,
Erik

From: Erik Jacobs [mailto:[email protected]]
Sent: maandag 10 april 2017 22:45
To: Roosemeyers Erik <[email protected]>
Cc: [email protected]
Subject: Re: high tcp retransmissions between pods on same openshift node

Hi Erik,

Are you using openshift-sdn or multitenant-sdn or something else? Are you 
running OpenShift Container Platform 3.1?

Are you just communicating with the pod IP directly?

---

ERIK JACOBS

PRINCIPAL TECHNICAL MARKETING MANAGER, OPENSHIFT

Red Hat Inc<https://www.redhat.com/>

[email protected]<mailto:[email protected]>    M: 
646.462.3745<tel:646.462.3745>     @: erikonopen
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On Tue, Mar 28, 2017 at 4:27 AM, Roosemeyers Erik 
<[email protected]<mailto:[email protected]>> wrote:
Hi all,

I'm testing network connectivity (speed and reliability) on a OpenShift cluster 
3.1.

I do this with 2 pods, each based on iperf3 Docker image.

First pod starts iperf3 as server, other one as iperf3 client with: iperf3 -c 
iperf3 -t 120 (iperf3 name of server pod).

What I notice is high throughput but also big retransmission rates:
eg.
duration              Transfer              Bandwidth         Retransmissions 
(TCP)
0.00-120.00 sec 214 GBytes         15.3 Gbits/sec   170478

If the pods are on 2 different nodes, the retransmission rate is smaller (as is 
throughput):

duration              Transfer              Bandwidth         Retransmissions 
(TCP)
0.00-120.00 sec 22.6 GBytes       1.62 Gbits/sec   3627

What I was wondering - what causes this higher retransmission rates ? (Mostly, 
it's a sign the are network problems but is it ?)

(I did some other tests, like deploying the containers via the Docker daemon 
onto 1 server. And even on a local laptop with only Docker daemon installed - 
and I always saw these tcp retransmission rates...)


Thanks in advance !

kind regards,
Erik

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