7.9 Information elements

09.603GPPGeneral Packet Radio Service (GPRS)GPRS Tunnelling Protocol GPT) across the Gn and Gp InterfaceRelease 1998TS

A signalling message may contain several information elements. The TLV (Type, Length, Value) or TV (Type, Value) encoding format shall be used for the GTP information elements. The information elements shall be sorted, with the Type fields in ascending order, in the signalling messages. The Length field contains the length of the information element excluding the Type and Length field.

For all the length fields, bit 8 of the lowest numbered octet is the most significant bit and bit 1 of the highest numbered octet is the least significant bit.

Within information elements, certain fields may be described as spare. These bits shall be transmitted with the value defined for them. To allow for future features, the receiver shall not evaluate these bits.

The most significant bit in the Type field is set to 0 when the TV format is used and set to 1 for the TLV format.

Figure 7: Type field for TV and TLV format

NOTE: Type value 7 (Decimal) is currently not used.

The following TLV Information Element type number ranges are reserved for GPRS charging protocol use (see GTP’ in GSM 12.15): 239-250; 252-254.

The following TV Information Element type number range is reserved for GPRS charging protocol use (see GTP’ in GSM 12.15): 117-127.

7.9.1 Cause

In a request, the Cause Value indicates the reason for the request. The Cause shall be included in the request message.

In a response, the Cause Value indicates the acceptance or the rejection of the corresponding request. In addition, the Cause Value may indicate what was the reason for the corresponding request. The Cause value shall be included in the response message.

‘Request accepted’ is returned when a GSN has accepted a signalling request.

‘Non-existent’ indicates a non-existent or an inactive PDP context.

‘IMSI not known’ indicates a non-existent MM context.

‘MS is GPRS Detached’ indicates an idle MM context.

‘MS is not GPRS Responding’ and ‘MS Refuses’ may be used by SGSN to reject a Network-Requested PDP Context Activation.

‘Version not supported’ is returned when the recipient does not recognise the version number in the request message.

‘Request IMSI’, ‘Request IMEI’, ‘Request IMSI and IMEI’ and ‘No identity needed’ are used by GGSN to notify SGSN what to do.

‘No resources available’ is a generic temporary error condition e.g. all dynamic PDP addresses are occupied or no memory is available.

‘Service not supported’ is a generic error indicated that the GSN do not support the requested service.

‘User authentication failed’ indicates that the external packet network has rejected the user’s service request.

‘System failure’ is a generic permanent error condition.

‘Roaming restriction’ indicates that the SGSN cannot activate the requested PDP context because of the roaming restrictions.

‘P-TMSI Signature mismatch’ is returned either if the P-TMSI Signature stored in the old SGSN does not match the value sent by the MS via the new SGSN or if the MS does not provide the P-TMSI Signature to the new SGSN while the old SGSN has stored the P-TMSI Signature for that MS.

‘Invalid message format’, ‘Mandatory IE incorrect’, ‘Mandatory IE missing’ and ‘Optional IE incorrect’ are indications of protocol errors described in the section Error handling.

‘GPRS connection suspended’ indicates that the GPRS activities of the mobile station are suspended.

‘Authentication failure’ indicates that the user authentication failed in the new SGSN.

Figure 8: Cause information element

Table 30: Cause values

Cause

Value (Decimal)

Request IMSI

0

Request IMEI

1

request

Request IMSI and IMEI

2

No identity needed

3

MS Refuses

4

MS is not GPRS Responding

5

For future use

6-48

Cause values reserved for GPRS charging protocol use

(see GTP’ in GSM 12.15)

49-63

For future use

64-127

acc

Request accepted

128

For future use

129-176

Cause values reserved for GPRS charging protocol use

(see GTP’ in GSM 12.15)

177-191

Non-existent

192

Invalid message format

193

response

rej

IMSI not known

194

MS is GPRS Detached

195

MS is not GPRS Responding

196

MS Refuses

197

Version not supported

198

No resources available

199

Service not supported

200

Mandatory IE incorrect

201

Mandatory IE missing

202

Optional IE incorrect

203

System failure

204

Roaming restriction

205

P-TMSI Signature mismatch

206

GPRS connection suspended

207

Authentication failure

208

User authentication failed

209

For future use

210-240

Cause values reserved for GPRS charging protocol use

(see GTP’ in GSM 12.15)

241-255

NOTE: With this coding, bits 8 and 7 of the Cause Value respectively indicate whether the message was a request or a response, and whether the request was accepted or rejected.

Table 31: Use of the Cause values

Cause

8

Value bits

7

Result

0

0

Request

0

1

For future use (Note)

1

0

Acceptance

1

1

Rejection

NOTE: The value ‘01’ is for future use and shall not be sent. If received in a response, it shall be treated as a rejection.

7.9.2 International Mobile Subscriber Identity (IMSI)

The IMSI shall be the subscriber identity of the MS. The IMSI is defined in GSM 03.03.

Figure 9: IMSI information element

The IMSI is TBCD-coded with a fixed length of 8 octets. Bits 8765 of octet n+1 encodes digit 2n, bits 4321 of octet n+1 encodes digit 2n-. Unused half octets shall be coded as binary ‘1 1 1 1’. Digits are packed contiguously with no internal padding.

7.9.3 Routeing Area Identity (RAI)

The RAI information element is given by:

Figure 10: RAI information element

If an administration decides to include only two digits in the MNC, then bits 5 to 8 of octet 3 are coded as "1111".

7.9.4 Temporary Logical Link Identity (TLLI)

The information element of the TLLI associated with a given MS and routeing area is given by:

Figure 11: TLLI information element

7.9.5 Packet TMSI (P-TMSI)

The Packet TMSI, unambiguously associated with a given MS and routeing area, is given by:

Figure 12: The Packet TMSI information element

7.9.6 Quality of Service (QoS) Profile

The Quality of Service (QoS) Profile shall include the values of the defined QoS parameters. The content and the coding of the QoS Profile is defined in GSM 04.08.

Figure 13: Quality of Service (QoS) Profile information element

7.9.7 Reordering Required

The Reordering Required information element states whether reordering by GTP is required or not.

Bits

Octets

8

7

6

5

4

3

2

1

1

Type=8 (Decimal)

2

1

1

1

1
Spare

1

1

1

Reord
Req

Figure 14: Reordering Required information element

Table 32: Reordering Required values

Reordering required

Value (Decimal)

No

0

Yes

1

7.9.8 Authentication Triplet

An Authentication triplet consists of a random string (RAND), a signed response (SRES) and a ciphering key (Kc) (see GSM 03.20).

Figure 15: Authentication Triplet information element

7.9.9 MAP Cause

The MAP Cause is a value that the GTP-MAP protocol-converting GSN relays transparently from HLR to the GGSN. The possible MAP Cause values for the appropriate messages are described in GSM 09.02.

Figure 16: MAP Cause information element

7.9.10 P-TMSI Signature

The P-TMSI Signature information element is provided by the MS in the Routing Area Update Request and Attach Request messages to the SGSN for identification checking purposes. The content and the coding of the P-TMSI Signature information element is defined in GSM 04.08.

Figure 17: P-TMSI Signature information element

7.9.11 MS Validated

The MS Validated information element indicates whether the new SGSN has successfully authenticated the MS.

Figure 18: MS Validated information element

Table 33: MS Validated values

MS Validated

Value

No

0

Yes

1

7.9.12 Recovery

The Recovery information element indicates if the peer GSN has restarted. The Restart Counter shall be the value described in the section Restoration and Recovery.

Figure 19: Restart counter information element

7.9.13 Selection mode

The Selection mode information element indicates the origin of the APN in the message.

Figure 20: Selection mode information element

Table 34: Selection mode values

Selection mode value

Value (Decimal)

MS or network provided APN, subscribed verified

0

MS provided APN, subscription not verified

1

Network provided APN, subscription not verified

2

For future use. Shall not be sent. If received, shall be interpreted as the value ‘2’.

3

7.9.14 Flow Label Data I

The Flow Label Data I information element contains the Flow label for data transmission requested by the receiver of the flow.

Figure 21: Flow Label Data information element

7.9.15 Flow Label Signalling

The Flow Label Signalling information element contains the Flow label for signalling requested by the receiver of the flow.

Figure 22: Flow Label Signalling information element

7.9.16 Flow Label Data II

The Flow Label Data II information element contains the Flow label for data transmission between old and new SGSN for a particular PDP context and is requested by the new SGSN.

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

Figure 23: Flow Label Data II information element

7.9.16A MS Not Reachable Reason

The MS Not Reachable Reason indicates the reason for the setting of the MNRG flag.

Bits

Octets

8

7

6

5

4

3

2

1

1

Type = 19 (Decimal)

2

Reason for Absence

Reason for Absence is defined in GSM 03.40

Figure 23A: MS Not Reachable Reason Information Element

7.9.17 Charging ID

The Charging ID is a unique four octet value generated by the GGSN when a PDP context is activated. A Charging ID is generated for each activated context. The Charging ID value 0 is reserved and shall not be assigned by the GGSN.

Figure 24: Charging ID information element

7.9.18 End User Address

The purpose of the End User Address information element shall be to supply protocol specific information of the external packet data network accessed by the GPRS subscriber.

The Length field value shall be 2 in an End User Address information element with an empty PDP Address.

The PDP Type defines the end user protocol to be used between the external packet data network and the MS and is divided into an Organization field and a Number field.

The PDP Type Organization is the organization that is responsible for the PDP Type Number field and the PDP Address format.

For X.25 the PDP Type Organization is ETSI and the PDP Type Number is 0 . The PDP Address shall be in the X.121 format for X.25. For PPP the PDP Type Organization is ETSI and the PDP Type Number is 1 and there shall be no address in the End User Address IE. In this case the address is negotiated later as part of the PPP protocol. If the PDP Type Organization is IETF, the PDP Type Number is a compressed number (i.e. the most significant HEX(00) is skipped) in the "Assigned PPP DLL Protocol Numbers" list in the most recent "Assigned Numbers" RFC (RFC 1700 or later). The most recent "Assigned PPP DLL Protocol Numbers" can also be found using the URL = ftp://ftp.isi.edu/in-notes/iana/assignments/ppp-numbers.

The PDP Address shall be the address that this PDP context of the MS is identified with from the external packet data network.

Figure 25: End User Address information element

Table 35: PDP Type Organization values

PDP Type Organization

Value (Decimal)

ETSI

0

IETF

1

All other values are reserved

Table 36: ETSI defined PDP Type values

PDP Type Number

Value (Decimal)

X.25

0

PPP

1

All other values are reserved

Figure 26: End User Address information element for IPv4

Figure 27: End User Address information element for IPv6

Figure 28: End User Address information element for X.25

NOTE: Digit 1 contains the first BCD coded digit of the X.121 address. If the X.121 address has an odd number of digits, the last BCD digit shall be padded with HEX(F).

Figure 29: End User Address information element for PPP

7.9.19 MM Context

The MM Context information element contains the Mobility Management, MS and security parameters that are necessary to transfer between SGSNs at the Inter SGSN Routeing Update procedure.

The Ciphering Key Sequence Number (CKSN) is described in GSM 04.08. Possible values are integers in the range [0; 6]. The value 7 is reserved.

The Used Cipher indicates the ciphering algorithm that is in use.

Kc is the ciphering key currently used by the old SGSN.

The Triplet array contains triplets encoded as the value in the Authentication Triplet information element.

The DRX parameter indicates whether the MS uses DRX mode or not.

MS Network Capability provides the network with information concerning aspects of the MS related to GPRS.

The DRX parameter includes only the value part of the DRX parameter IE defined in GSM 04.08 and the MS Network Capability includes the length and the value part of the MS network capability IE defined in GSM 04.08. The two octet Container Length holds the length of the Container, excluding the Container Length octets.

The Container contains one or several optional information elements as described in the sub-clause ‘Overview’, from the clause ‘General message format and information elements coding’ in GSM 04.08.

NOTE: k is the value of the MS Network Capability length indicator (GSM 04.08)

Table 37: Used Cipher values

Cipher Algorithm

Value (Decimal)

No ciphering

0

GEA/1

1

7.9.20 PDP Context

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 which is associated with the NSAPI.

Transaction Identifier is the 4 bit Transaction Identifier used in the GSM 04.08 Session Management messages which control this PDP Context. The latest Transaction Identifier sent from SGSN to MS is stored in the PDP context IE.

Reordering Required (Order) indicates whether the SGSN shall reorder T-PDUs before delivering the T-PDUs to the MS.

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.

Quality of Service Subscribed (QoS Sub), Quality of Service Requested (QoS Req) and Quality of Service Negotiated (QoS Neg) are encoded as described in section ‘Quality of Service (QoS) Profile’.

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 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 Send N-PDU Number is used only when acknowledged peer-to-peer LLC operation is used for the PDP context. The Send N-PDU Number is the N-PDU number to be assigned by SNDCP to the next downlink 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 uplink 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 Flow Label Signalling is the Flow Label used between the old SGSN and the GGSN in uplink direction for signalling purpose. It shall be used by the new SGSN within the GTP header of the Update PDP Context Request message.

The PDP Type Organization 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, IPv6 or X.25.

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

The old SGSN includes the GGSN Address for signalling that it has received from GGSN at PDP context activation or update.

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 which shall be set to 0 by the sending side and which shall not be evaluated by the receiving side.

1

Type = 130 (Decimal)

2-3

Length

4

Res-erved

VAA

Res-erved

Order

NSAPI

5

X

X

X

X

SAPI

6-8

QoS Sub

9-11

QoS Req

12-14

QoS Neg

15-16

Sequence Number Down (SND)

17-18

Sequence Number Up (SNU)

19

Send N-PDU Number

20

Receive N-PDU Number

21-22

Uplink Flow Label Signalling

23

Spare 1 1 1 1

PDP Type Organization

24

PDP Type Number

25

PDP Address Length

26-m

PDP Address [0..63]

m+1

GGSN Address for signalling Length

(m+2)-n

GGSN Address for signalling [4..16]

n+1

APN length

(n+2)-o

APN

o+1

Spare (sent as 0 0 0 0)

Transaction Identifier

Figure 32: PDP Context information element

Table 38: Reordering Required values

Reordering Required

Value (Decimal)

No

0

Yes

1

Table 39: VPLMN Address Allowed values

VPLMN Address Allowed

Value (Decimal)

No

0

Yes

1

7.9.21 Access Point Name

The Access Point Name is information from the MS or SGSN , that may be used by the GGSN to differentiate between accesses to different external packet data networks using the same PDP Type.

The Access Point Name contains a logical name which is the APN Network Identifier (see GSM 03.60). It is coded as in the value part defined in GSM 04.08 (i.e. the GSM 04.08 IEI and GSM 04.08 octet length indicator are not included).

Figure 33: Access Point Name information element

7.9.22 Protocol Configuration Options

The Protocol Configuration Options contains external network protocol options that may be necessary to transfer between the GGSN and the MS. The content and the coding of the Protocol Configuration is defined in octet 3-z of the Protocol Configuration Options in GSM 04.08.

Figure 34: Protocol Configuration Options information element

7.9.23 GSN Address

The GSN Address information element contains the address of a GSN as defined in GSM 03.03. The Address Type and Address Length fields from 03.03 are not included in the GSN Address field.

Figure 35: GSN Address information element

7.9.24 MS International PSTN/ISDN Number (MSISDN)

The MS international ISDN numbers are allocated from the CCITT Recommendation E.164 numbering plan, see GSM 03.03. The MSISDN is coded according to the contents of ISDN-AddressString data type defined in GSM 09.02. The MSISDN shall be in international format and the “nature of address indicator” shall indicate “international number”.

Figure 36: MSISDN information element

7.9.25 Charging Gateway Address

The Charging Gateway Address information element contains an IP address of a Charging Gateway.

Figure 37: Charging Gateway Address information element

7.9.26 Private Extension

The Private Extension information element contains vendor specific information. The Extension Identifier is a value defined in the Private Enterprise number list in the most recent "Assigned Numbers" RFC (RFC 1700 or later).

This is an optional information element that may be included in any signalling message. A signalling message may include more than one information element of the Private Extension type.

Figure 38: Private Extension information element