DDoS: How to find average connection count per IP in 5 minute window?

[zachsisinst]

Hi friends, I am trying to piece together some splunk searches across application logs to try and piece together what 'normal' traffic patterns look like, vs DDoS attacking IP addresses. The end goal is to answer the question: "For each IP that connects to our application, what is the average connection count within a 5m span, across a 2 hour period? What are the outlier ( greater than average) 5m span connection counts? 

I have the following timechart which has been useful, but I'm sure there is a better way to do this. 

index=myapplicationindex sourcetype=_json cluster=cluster23 | timechart span=5m count by x_forwarded_for where count > 75

[PickleRick]

Use streamstats with time_window=5m (there is however an upper limit on events within the window - by default it's 10000 - so if you accumulate more than this number, your search may fail or produce erroneous results).