Finally it should be mentioned that according to the intrinsic differences in WLAN 802.11 and UTRAN technologies the condition of access that these two technologies provide for IMS services are not exactly the same. 3GPP has not considered resource reservation for WLAN accesses to IMS services. Therefore there is no equivalent interface for Go in WLAN case. As mentioned before, Go is an interface between PDF and GGSN in order to transfer the policy decisions for resource reservation. The differences between WLAN 802.11 and 3G technologies that should be taken into account for access to 3G services including IMS are listed in table 4