08.163GPPBase Station System (BSS) - Serving GPRS Support Node (SGSN) interfaceGeneral Packet Radio Service (GPRS)Network serviceRelease 1999TS

This clause is not applicable to the Sub-Network Service protocol.

9.1 General structure of a PDU

This subclause defines the general structure of the PDUs on the Gb interface.

The general PDU structure is composed of:

a) a PDU type information element; and

b) other information elements, as required.

The PDU type IE occupies the first octet position in the PDU.

This general structure and the numbering convention used on the Gb interface are illustrated in figure 6/3GPP TS 08.16. The bits are grouped into octets. The bits of an octet are shown horizontally and are numbered from 1 to 8. Multiple octets are shown vertically and are numbered from 1 to n.

The octets shall be transmitted by increasing order of octet number. Within each octet, the bits shall be transmitted by increasing order of bit number i.e. bit 1 of octet 1 shall be transmitted first, bit 8 of octet n shall be transmitted last.

Figure 7/3GPP TS 08.16: General PDU structure and numbering convention

Each PDU definition includes a table listing the information elements (IEs) known in the PDU and the order of their appearance in the PDU. Unless specified otherwise in the PDU descriptions, a particular information element shall not be present more than once in a given PDU. All information elements that may be repeated are explicitly indicated.

For each information element the table indicates:

a) The name of the information element (which may give an idea of the semantics of the element).

b) Possibly a reference to another GSM Technical Specification where the information element is described.

c) The presence requirement indication (M, C, or O) for the IE as defined in clause "General protocol error handling".

d) The format (T, L, V) of the information element. See further description of the type (T), length (L) and V (value) fields in subclause "General structure of the information elements".

e) The length of the information element (or permissible range of lengths), in octets, in the PDU, where "?" means that the maximum length of the IE is only constrained by the lower layer protocol. This indication is non-normative. The indicated length includes all the T, L, V fields present in the IE.

f) Subclauses specifying, where appropriate, conditions for IEs with presence requirement C or O in the relevant PDU which together with other conditions specified in 3GPP TS 08.16 define when the information elements shall be included or not, what non-presence of such IEs means, and – for IEs with presence requirement C – the static conditions for presence and/or non-presence of the IEs, see clause "General protocol error handling".

9.2 Network Service Control PDUs

The Network Service Control PDUs are also referred to as NS PDUs in the rest of this Technical Specification.

9.2.1 NS-ALIVE

This PDU is used to test an NS-VC.

PDU type: NS-ALIVE

Direction: BSS to SGSN, SGSN to BSS

Table 2/3GPP TS 08.16: NS-ALIVE PDU contents

9.2.2 NS-ALIVE-ACK

This PDU acknowledges a received NS-ALIVE PDU and is sent on the NS-VC where the NS-ALIVE PDU was received.

PDU type: NS-ALIVE-ACK

Direction: SGSN to BSS, BSS to SGSN

Table 3/3GPP TS 08.16: NS-ALIVE-ACK PDU contents

9.2.3 NS-BLOCK

This PDU indicates that an NS-VC shall be blocked at the recipient entity.

PDU type: NS-BLOCK

Direction: BSS to SGSN, SGSN to BSS

Table 4/3GPP TS 08.16: NS-BLOCK PDU contents

9.2.4 NS-BLOCK-ACK

This PDU acknowledges that an NS-VC has been blocked for use.

PDU type: NS-BLOCK-ACK

Direction: SGSN to BSS, BSS to SGSN

Table 5/3GPP TS 08.16: NS-BLOCK-ACK PDU contents

9.2.5 NS-RESET

This PDU indicates that the NS peer entity is trying to reset one NS-VCs.

PDU type: NS-RESET

Direction: BSS to SGSN, SGSN to BSS

Table 6/3GPP TS 08.16: NS-RESET PDU contents

Typical cause values are: O&M intervention, Equipment failure.

9.2.6 NS-RESET-ACK

This PDU acknowledges the reset of the indicated NS-VCs.

PDU type: NS-RESET-ACK

Direction: BSS to SGSN, SGSN to BSS

Table 7/3GPP TS 08.16: NS-RESET-ACK PDU contents

9.2.7 NS-STATUS

This PDU is used to report error conditions.

PDU type: NS-STATUS

Direction: SGSN to BSS, BSS to SGSN

Table 8/3GPP TS 08.16: NS-STATUS PDU contents

9.2.7.1 Static conditions for NS-VCI

The "NS-VCI" IE shall be included when the "Cause" IE is set to one of the following values:

a) "NS-VC blocked",

b) "NS-VC unknown",

and shall not be included otherwise.

9.2.7.2 Static conditions for NS PDU

The "NS PDU" IE shall be included if the NS-STATUS message is sent in response to a received NS PDU within which an error was detected i.e. when the "Cause" IE is set to one of the following values:

a) "Semantically incorrect PDU",

b) "PDU not compatible with the protocol state",

c) "Protocol error – unspecified",

d) "Invalid essential IE",

e) "Missing essential IE",

and shall not be included otherwise.

This is the whole PDU received with error. This PDU may be truncated if it exceeds the information carrying capacity of the NS.

9.2.7.3 Static conditions for BVCI

The "BVCI" IE shall be included when the "Cause" IE is set to one of the following values:

a) "BVCI unknown on that NSE",

and shall not be included otherwise.

9.2.8 NS-UNBLOCK

This PDU indicates that an NS-VC shall be unblocked at the recipient entity.

PDU type: NS-UNBLOCK

Direction: BSS to SGSN, SGSN to BSS

Table 9/3GPP TS 08.16: NS-UNBLOCK PDU contents

9.2.9 NS-UNBLOCK-ACK

This PDU acknowledges that an NS-VC has been unblocked.

PDU type: NS-UNBLOCK-ACK

Direction: SGSN to BSS, BSS to SGSN

Table 10/3GPP TS 08.16: NS-UNBLOCK-ACK PDU contents

9.2.10 NS-UNITDATA

This PDU transfers one NS SDU between the BSS and SGSN.

PDU type: NS-UNITDATA

Direction: BSS to SGSN, SGSN to BSS

Table 11/3GPP TS 08.16: NS-UNITDATA PDU contents

The length of the "NS SDU" information element shall be derived by the Network Service Control entity from the length of the complete NS-UNITDATA PDU provided by the Sub-Network Service entity to the Network Service Control entity.