You will need to use a REST client and set it with the following parameters:
URL: http://<DA_HOST>:8581/rest/discoverydefaultconfig/{itemID}
Method: PUT
Body:
<DiscoveryDefaultConfig version="1.0.0">
<IcmpTimeout>3500</IcmpTimeout>
<IcmpTryCount>4</IcmpTryCount>
<IcmpPacketSize>32</IcmpPacketSize>
</DiscoveryDefaultConfig>
Then send this to the Data Aggregator (<DA_HOST>).
After performing this action with a REST interface the ICMP parameters will be changed