9 General PDU definitions and contents
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.
|
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
|
|
octet 1 |
PDU type |
|||||||
|
octets 2, 3, …n |
other information elements |
|||||||
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
|
Information element |
Reference |
Presence |
Format |
Length |
|
PDU type |
M |
V |
1 |
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
|
Information element |
Reference |
Presence |
Format |
Length |
|
PDU type |
M |
V |
1 |
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
|
Information element |
Reference |
Presence |
Format |
Length |
|
PDU type |
M |
V |
1 |
|
|
Cause |
M |
TLV |
3 |
|
|
NS-VCI |
M |
TLV |
4 |
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
|
Information element |
Reference |
Presence |
Format |
Length |
|
PDU type |
M |
V |
1 |
|
|
NS-VCI |
M |
TLV |
4 |
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
|
Information element |
Reference |
Presence |
Format |
Length |
|
PDU type |
M |
V |
1 |
|
|
Cause |
M |
TLV |
3 |
|
|
NS-VCI |
M |
TLV |
4 |
|
|
NSEI |
M |
TLV |
4 |
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
|
Information element |
Reference |
Presence |
Format |
Length |
|
PDU type |
M |
V |
1 |
|
|
NS-VCI |
M |
TLV |
4 |
|
|
NSEI |
M |
TLV |
4 |
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
|
Information element |
Reference |
Presence |
Format |
Length |
|
PDU type |
M |
V |
1 |
|
|
Cause |
M |
TLV |
3 |
|
|
NS-VCI |
C |
TLV |
4 |
|
|
NS PDU |
C |
TLV |
3-? |
|
|
BVCI |
C |
TLV |
4 |
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
|
Information element |
Reference |
Presence |
Format |
Length |
|
PDU type |
M |
V |
1 |
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
|
Information element |
Reference |
Presence |
Format |
Length |
|
PDU type |
M |
V |
1 |
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
|
Information element |
Reference |
Presence |
Format |
Length |
|
PDU type |
M |
V |
1 |
|
|
spare octet |
M |
V |
1 |
|
|
BVCI |
M |
V |
2 |
|
|
NS SDU |
M |
V |
1-? |
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.