The term DMZ comes from military origins, Demilitarized Zone, in netwoking terminology it essentially means an interface to the outside world which is free from all restrictions i.e all ports open, now torrents are community driven, so openess is very important. To enable DMZ on most modems follow the steps given below:
1. Go to network settigs-> local area connections and go to the properties of TCP/IP protocol and change your IP to any local address (192.168.1.XXX) and set your default gateway to your modems IP (in my case 192.168.1.1)
2. Go to your modem's configuration page (in my case http://192.168.1.1) you will be prompted for a username and password (usually "admin" "admin", if not contact service provider).
3. Here serarch for NAT settings, under which DMZ host will be there, set the DMZ host to your computers IP and reboot modem.
This method made my torrents continuos (reliable speeds) and increased speeds by about 40%.
Hope it works for you!!