7.7.55 MBMS UE Context

29.0603GPPGeneral Packet Radio Service (GPRS)GPRS Tunnelling Protocol (GTP) across the Gn and Gp interfaceRelease 17TS

The MBMS UE Context information element contains UE-specific information related to a particular MBMS service that the UE has joined, that are necessary to transfer between SGSNs at the Inter SGSN Routeing Area Update procedure and Inter SGSN SRNS Relocation procedure.

Linked NSAPI is an integer value in the range [0, 15].

The Linked NSAPI identifies the PDP Context used by the UE to carry IGMP/MLD signalling.

Enhanced NSAPI is an integer value in the range [128; 255].

The Enhanced NSAPI points out the affected MBMS UE context.

The Uplink Tunnel Endpoint Identifier Control Plane is the Tunnel Endpoint Identifier used between the old SGSN and the GGSN in up link direction for control plane purpose. It shall be used by the new SGSN within the GTP header of the Update MBMS Context Request message.

The PDP Type Organisation and PDP Type Number are encoded as in the End User Address information element.

The PDP Address Length represents the length of the PDP Address field, excluding the PDP Address Length octet.

The PDP Address is an octet array with a format dependent on the PDP Type. The PDP Address is encoded as in the End User Address information element.

The GGSN Address Length represents the length of the GGSN Address field, excluding the GGSN Address Length octet.

When forwarding the GGSN address to another SGSN (in the MBMS UE Context IE in Forward Relocation Request or SGSN Context Response message), the IPv4/IPv6 capable SGSN shall include GGSN address according to the IP version capability of the receiving SGSN. Determining the Capability of the receiving SGSN is implementation dependent.

The old SGSN includes the GGSN Address for control plane that it has received from GGSN at MBMS service activation or update. If the new SGSN is IPv6 capable and the old SGSN has IPv6 control plane address of the GGSN available, the old IPv4/IPv6 capable SGSN includes the IPv6 GGSN control plane address in the field GGSN Address for control plane. If the new SGSN is IPv4 only capable or the old SGSN does not have any IPv6 GGSN address for control plane, the old SGSN includes the IPv4 GGSN Address in the field GGSN Address for control plane.

The APN is the Access Point Name in use in the old SGSN.

The Transaction Identifier is the 4 or 12 bit Transaction Identifier used in the 3GPP TS 24.008 [5] Session Management messages which control this MBMS UE Context. If the length of the Transaction Identifier is 4 bit, the second octet shall be set to all zeros. The encoding is defined in 3GPP TS 24.007 [3]. The latest Transaction Identifier sent from SGSN to MS is stored in the MBMS UE context IE.

NOTE: Bit 5-8 of the first octet in the encoding defined in 3GPP TS 24.007 [3] is mapped into bit 1-4 of the first octet in this field.

The spare bits shall be set as indicated in the table below by the sending side and shall not be evaluated by the receiving side.

Bits
Octets	8	7	6	5	4	3	2	1
1	Type = 156 (Decimal)
2-3	Length
4	Linked NSAPI				Spare (sent as 0 0 0 0)
5-8	Uplink Tunnel Endpoint Identifier Control Plane
9	Enhanced NSAPI
10	Spare (sent as 1 1 1 1)				PDP Type Organisation
11	PDP Type Number
12	PDP Address Length
13-ｍ	PDP Address [0..63]
ｍ+1	GGSN Address for control plane Length
(ｍ+2)-ｎ	GGSN Address for control plane [4..16]
n+1	APN length
(n+2)-o	APN
(o+1)	Spare (sent as 0 0 0 0)				Transaction Identifier
o+2	Transaction Identifier

Figure 7.7.55.1: MBMS UE Context Information Element