參考attach過程中PGW和PCRF之間的IP-CAN的建立部分說明：
The IMSI, APN, UE IP address, User Location Information (ECGI), UE Time Zone, Serving Network, RAT type, APN-AMBR, Default EPS Bearer QoS are provided to the PCRF by the PDN GW if received by the previous message. The User Location Information and UE Time Zone are used for location based charging. For emergency attached UEs which are unauthenticated the PDN GW provides the IMEI as the UE Identity instead of IMSI, to the PCRF.
The PCRF may modify the APN-AMBR and the QoS parameters (QCI and ARP) associated with the default bearer in the response to the PDN GW