[CentOS] Monitor speed between client and server, netperf?

Hi,

    Want to know what is the best tools to monitor network connection 
speed between client PC and my server. As I need to know if the network 
latency.
I know use zabbix to monitor CPU/member and others of server. However,
    1. For the connection speed monitor is there any tools can do this?
    2. I tried netperf, it's good.  I have to write a cron job in my 
client PC to report the speed? is this a correct way to do?
    3. If use netperf and cron job do connection speed test every 5 
mins, is that impact my server network throughput as I guess it is 
sending really data between server and client.
    Could you help to point me a right way to move on, thank you very much.

Best Regards,
Su Heng