7.7.29 PDP Context

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

The PDP Context information element contains the Session Management parameters, defined for an external packet data network address, that are necessary to transfer between SGSNs at the Inter SGSN Routeing Area Update procedure.

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

The NSAPI points out the affected PDP context.

The SAPI indicates the LLC SAPI that is associated with the NSAPI.

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 PDP 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 PDP 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.

Reordering Required (Order) indicates whether the SGSN shall reorder T-PDUs before delivering the T-PDUs to the MS. When the Quality of Service Negotiated (QoS Neg) is Release 99, the Reordering Required (Order) shall be ignored by receiving entity.

The VPLMN Address Allowed (VAA) indicates whether the MS is allowed to use the APN in the domain of the HPLMN only or additionally the APN in the domain of the VPLMN.

The Activity Status Indicator (ASI) indicates whether there is an active RAB/PFC associated with the PDP Context. This indicator is of interest when the PDP Context IE is included in a FORWARD RELOCATION REQUEST message or an inter SGSN RAU (SGSN Context Response) triggered by a Directed Signalling Connection Re-establishment.

NOTE: If the ASI indicates that there is no active RAB/PFC associated with the concerned PDP Context at the source side, no RAB/PFC needs to be set up on the target side.

The Extended End User Address (EA) indicates, when set to 1, that the MS uses Dual Stack IPv4v6 address and that octets "p+3" to "r" shall be included and contain the second part of the IPv4v6 Address, i.e. PDP Type Number at the Octet "3q+25" shall be set to HEX(21) indicating IPv4 and PDP Type Number at the Octet "p+3" shall be set to HEX(57) indicating IPv6, or vice versa.

NOTE: 3GPP TS 23.060 [4] assumes that if used, the IPv4v6 type should be supported by all SGSNs in a PLMN.

The QoS Sub Length, QoS Req Length and QoS Neg Length represent respectively the lengths of the QoS Sub, QoS Req and QoS Neg fields, excluding the QoS Length octet.

The Quality of Service Subscribed (QoS Sub), Quality of Service Requested (QoS Req) and Quality of Service Negotiated (QoS Neg) are encoded as described in clause "Quality of Service (QoS) Profile". Their minimum length is 4 octets; their maximum length may be 255 octets.

The Sequence Number Down is the number of the next T-PDU that shall be sent from the new SGSN to the MS. The number is associated to the Sequence Number from the GTP Header of an encapsulated T-PDU. The new SGSN shall ignore Sequence Number Down when the PDP context QoS profile does not require transmission order to be preserved. In this case the new SGSN shall not include Sequence number field in the G-PDUs of the PDP context.

The Sequence Number Up is the number that new SGSN shall use as the Sequence Number in the GTP Header for the next encapsulated T-PDU from the MS to the GGSN. The new SGSN shall ignore Sequence Number Up when the PDP context QoS profile does not require transmission order to be preserved. In this case, the new SGSN shall not include Sequence number field in the G-PDUs of the PDP context.

The Send N-PDU Number is used only when acknowledged peer-to-peer LLC operation is used for the PDP context. Send N-PDU Number is the N-PDU number to be assigned by SNDCP to the next down link N-PDU received from the GGSN. It shall be set to 255 if unacknowledged peer-to-peer LLC operation is used for the PDP context.

The Receive N-PDU Number is used only when acknowledged peer-to-peer LLC operation is used for the PDP context. The Receive N-PDU Number is the N-PDU number expected by SNDCP from the next up link N-PDU to be received from the MS. It shall be set to 255 if unacknowledged peer-to-peer LLC operation is used for the PDP 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 PDP Context Request message.

The GGSN Address for User Traffic and the Uplink Tunnel Endpoint Identifier Data I are the GGSN address and the Tunnel Endpoint Identifier used between the old SGSN and the GGSN in uplink direction for user plane traffic on a PDP context. They shall be used by the new SGSN to send uplink user plane PDU to the GGSN until new GGSN address for User Traffic is possibly received from GGSN (in Update PDP Context Response).

The GGSN Address for control plane and the GGSN Address for User Traffic may be IP addresses of the same type or different types (e.g. IPv4 control plane address and IPv6 user traffic address).

The PDP Context Identifier is used to identify a PDP context for the subscriber.

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 if the PDP Type is IPv4 or IPv6.

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

When forwarding the GGSN addresses to another SGSN (in PDP Context IE in Forward Relocation Request or SGSN Context Response message), the IPv4/IPv6 capable SGSN shall include GGSN addresses 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 PDP context 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 use of Ipv6 addressing in pre-Release 5 nodes can cause interoperability problems and as such the use of IPv6 GSN addressing is not recommended in pre-Release 5.

The APN is the Access Point Name in use in the old SGSN. This APN field shall be composed of the APN Network Identifier part and the APN Operator Identifier part.

The spare bits x indicate unused bits that shall be set to 0 by the sending side and which shall not be evaluated by the receiving side.

Bits
Octets	8	7	6	5	4	3	2	1
1	Type = 130 (Decimal)
2-3	Length
4	EA	VAA	ASI	Order	NSAPI
5	X	X	X	X	SAPI
6	QoS Sub Length
7 – (q+6)	QoS Sub [4..255]
q+7	QoS Req Length
(q+8)-(2q+7)	QoS Req [4..255]
2q+8	QoS Neg. Length
(2q+9)-(3q+8)	QoS Neg [4..255]
(3q+9)-(3q+10)	Sequence Number Down (SND) (NOTE)
(3q+11)-(3q+12)	Sequence Number Up (SNU) (NOTE)
3q+13	Send N-PDU Number (NOTE)
3q+14	Receive N-PDU Number (NOTE)
(3q+15)-(3q+18)	Uplink Tunnel Endpoint Identifier Control Plane
(3q+19)-(3q+22)	UplinkTunnel Endpoint Identifier Data I
3q+23	PDP Context Identifier
3q+24	Spare 1 1 1 1				PDP Type Organisation
3q+25	PDP Type Number
3q+26	PDP Address Length
(3q+27)-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	GGSN Address for User Traffic Length
(n+2)-o	GGSN Address for User Traffic [4..16]
o+1	APN length
(o+2)-p	APN
p+1	Spare (sent as 0 0 0 0)				Transaction Identifier
p+2	Transaction Identifier
p+3	PDP Type Number
p+4	PDP Address Length
(p+5)-r	PDP Address [0..63]
NOTE: This field shall not be evaluated when the PDP context is received during UMTS intra system handover/relocation.

Figure 43: PDP Context Information Element

Table 48: Reordering Required Values

Reordering Required	Value (Decimal)
No	0
Yes	1

Table 49: VPLMN Address Allowed Values

VPLMN Address Allowed	Value (Decimal)
No	0
Yes	1

Table 49A: Activity Status Indicator Values

Active RAB/PFC exists	Value (Decimal)
Yes	0
No	1