Is there an OC3 interface available for the 3945 ISR2 for a full OC3/155Mb IP WAN port? I am familiar with the PA-POS-1OC3 Packet/SONET Module that I have used on 7000 series but this appears incompatible with the 3900's. The only 3900 OC3 module I see is the NM-1A-OC3-POM which states it is an ATM Module. My WAN interface will be IP only, no ATM. Is there another option?