AH_App protocol interpretation

AH_App protocol interpretation

I have installed netflow to trace the reason for my line congestion.  What I can find from the results is that AH_App is utilizing more than 60% of my bandwidth, the source being the serial interface of the router and destination the serial interface of the remote router.  I cannot understand what traffic is this.  I have IPSec site to site VPN configured between both routers.  Can you help please...Its urgent network is congested and I cant understand the protocol in question.

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