How to get RTT with sFlow?

[Sara Escribano]

Hi, I'm new using sFlow and I'm having several problems to get some parameters of my flow.

First of all, I defined my flow like this:

curl-H "Content-Type:application/json" -X PUT --data "{keys:'ipsource,ipdestination,tcpsourceport,tcpdestinationport,tcpwindow', value:'bytes', log:true}" http://127.0.0.1:8008/flow/tcpbueno/json

And then I tried to GET the information using:

curl http://127.0.0.1:8008/flow/tcpbueno/json

Everything is okay and I get on sFlow the information I need, but when I try to get the parameter "tcprtt" which is included in TCP Info (https://sflow-rt.com/define_flow.php), it's impossible and there are no changes in the real time analysis. (I'm analysing the traffic between two namespaces, sending TCP packets between them).

So I want to know how to write correctly the commands in order to get the parameter tcprtt.

Thanks in advance.

[Peter Phaal]

The extended_tcp_info can only be filled in at the end point of a TCP connection (i.e. by host). The Host sFlow (sflow.net) agent on Linux can be configured to populate this structure:

https://blog.sflow.com/2016/10/network-performance-monitoring.html

I see you also posted this question to the sFlow-RT mailing list (https://sflow-rt.com/community.php). I'll provide additional information on configuring sFlow-RT to report on tcprtt there.

[Sara Escribano]

Hi again!

But I'm not using Javascript, I'm doing everything by shell and I'm having several troubles transcripting setFlow functions to shell (because I have no idea), but above all things, how do I have to introduce that tcp_rtt_country, because I tried:

curl -H "Content-Type:application/json" -X PUT --data "{keys:'country:[if:tcpdirection:sent:ipdestinacion:ipsource]', value:'tcprtt', t:20}" http://127.0.0.1:8008/flow/tcp_rtt_country/json  

and GET it with

curl http://127.0.0.1:8008/flow/tcp_rtt_country/json 

And I obtained this:

Of course, it has to be wrong because I want the tcprtt value, not a string saying "tcprtt" or something like that. I want to remark I have no idea about this and I only want to get latency, jitter and wrong packets from a flow

Do you know where did I make the mistake?

Thanks in advance :)

[Peter Phaal]

Please see reply on the sFlow-RT mailing list (https://sflow-rt.com/community.php)