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On-Demand, Non-GBR, QCI=8. Used for XCAP traffic, browsing, e-mail clients, MMS, etc.

On AT&T LTE RAN, the device shall support at least 5 simultaneous bearers

AT&T’s LTE Phase 3 deployment is focused on LTE VoIP build on IMS 3GPP Release 9. IMS VOIP over Wi-Fi is currently out of scope, but is something AT&T will consider at a future date.

The UE shall support implicit registration of at least 6 public IDs using the P-Associated-URI header per the procedures in 3GPP TS 24.229 section 5.1.1.2.1.

The UE must include an IMEI URN in the “+sip.instance”header field parameter (Instance ID) of the Contact address. Per spec:GSMA IR.92, Section 2.2.1; 3GPP 23.003, Section 13.8.

When performing IMS registration, VoLTE-capable UEs must include the IMS Communication Service Identifier (ICSI) value for IMS Multimedia Telephony Service- urn:urn-7:3gppservice.ims.icsi.mmtel. Per specs: GSMA IR.92; 3GPP TS 24.173; 3GPP TS 24.229, Section 5.1.1.2.1.

If the UE has attempted to register to every known P-CSCF and received temporary errors, or received a temporary error when attempting to establish a connection to the IMS APN, it shall calculate a wait time before attempting further IMS registrations. The timer value shall be determined using the procedures in RFC 5626 section 4.5. In this implementation, base-time shall be set to 120 seconds and max-time shall be 7200 seconds. When this timer expires, the UE shall attempt an IMS registration using the first P-CSCF from the list of discovered proxies.

On receiving a 305 response to a registration request, the UE shall follow the procedures defined in 3GPP TS 24.229 starting from the top of the existing P-CSCF list for the next initial registration attempt.

If the UE fails to register to a P-CSCF due to the expiration of Timer F or by receiving a SIP error code of 408, 500, 503, or 504, it shall attempt an initial IMS registration on the next P-CSCF in the discovered list. The UE shall honor any Retry-After header received, and use the associated value as the wait time before the next registration attempt. The UE shall proceed through the P-CSCF list in a circular manner until every known address has been tried for this registration attempt.