Dtmf problem with duplicating digits

Calling from any type of phone anywhere, dtmf numbers get duplicated especially during peak internet hours. I believe this is occuring because part of the dtmf information is getting passed through a router between my network and my sip provider and then is getting delayed. Which my Asterisk server then reads as two seperate dtmf keypresses. Where can I edit the dtmf inter-digit delay? I would like to increase the default value for troubleshooting and/or a temporary fix.