08.183GPPBase Station System (BSS) - Serving GPRS Support Node (SGSN)BSS GPRS ProtocolGeneral Packet Radio Service (GPRS)Release 1999TS
8a.1 Create BSS PFC procedure
If the BSS receives a request to transfer an uplink or downlink LLC PDU for which it currently does not have a BSS packet flow context and the PFI does not indicate best-effort or SMS or signalling then the BSS may send a DOWNLOAD-BSS-PFC PDU to the SGSN and start timer T6. In the uplink case the TLLI, optional Radio Priority, and optional Packet Flow ID are received from the MS as defined in 3GPP TS 04.60. Until the BSS receives the BSS PFC the BSS shall handle uplink and downlink transfers according to a best-effort default aggregate BSS QoS profile. For uplink transfers the best-effort default profile is specific to the radio priority level.
If the BSS does not receive a PFI from the MS, e.g. from a R97 or R98 MS, the BSS shall not send a DOWNLOAD-BSS-PFC PDU to the SGSN. In this case the QoS Profile IE is utilized instead.
Following a DOWNLOAD-BSS-PFC PDU, the SGSN shall send a CREATE-BSS-PFC PDU to the BSS with a requested Aggregate BSS QoS Profile and start timer T7. On receipt of CREATE-BSS-PFC PDU the BSS stops timer T6 and responds with a CREATE-BSS-PFC-ACK PDU containing the negotiated Aggregate BSS QoS Profile. The BSS may restrict the requested ABQP given its capabilities and the current load. The SGSN may include the Service UTRAN CCO (Cell Change Order) information element in the PDU (relevant if the network initiated cell change order to UTRAN procedure is used). If this information element is received in both the CREATE-BSS-PFC PDU and the DL-UNITDATA PDU, the information element received in the DL-UNITDATA PDU shall take precedence.
The SGSN may also initiate the Create BSS PFC procedure. It is not required that the SGSN receive a DOWNLOAD-BSS-PFC PDU before sending a CREATE-BSS-PFC request.
The BSS may return a CREATE-BSS-PFC-NACK with a cause if it is unable to create or modify the PFC. On receipt of the CREATE-BSS-PFC-ACK or CREATE-BSS-PFC-NACK PDU the SGSN shall stop timer T7.
The Packet Flow Timer (PFT) is provided to the BSS by the SGSN. It is defined as the maximum time the BSS may hold the PFC during periods of inactivity for a PFC. The timer is started upon the receipt of a CREATE-BSS-PFC PDU and restarted after the transmission of an uplink PDU for that PFC. The timer is also restarted upon the transfer of the corresponding PFC from an old to a new cell.
If a CREATE-BSS-PFC PDU is received for an MS which has a BSS PFC in the BSS, then this shall be interpreted by the BSS as a request to modify the existing PFC.
8a.1.1 Abnormal conditions
If the SGSN receives a DOWNLOAD-BSS-PFC PDU with an unknown PFI it shall not respond with a CREATE-BSS-PFC PDU.
If a CREATE-BSS-PFC PDU is not received for a DOWNLOAD-BSS-PFC PDU within T6 seconds, then the DOWNLOAD-BSS-PFC PDU shall be repeated a maximum of DOWNLOAD-BSS-PFC-RETRIES attempts. After DOWNLOAD-BSS-PFC-RETRIES + 1 attempts the procedure is stopped and the O&M system is informed. If a BSS PFC is not received then the BSS shall handle uplink and downlink transfers according to a best-effort default aggregate BSS QoS profile.
If a CREATE-BSS-PFC-ACK or CREATE-BSS-PFC-NACK PDU is not received in response to a CREATE-BSS-PFC PDU within T7 seconds, then the CREATE-BSS-PFC PDU shall be repeated a maximum of CREATE-BSS-PFC-RETRIES attempts. After CREATE-BSS-PFC-RETRIES+1 attempts the procedure is stopped and the O&M is informed.
If the BSS is unable to create the PFC then a CREATE-BSS-PFC-NACK PDU is returned with a cause value (e.g. Cause value: PFC create failure). The SGSN shall stop the Create BSS PFC procedure.
8a.2 Modify BSS PFC procedure
The BSS may request modification of the contents of an existing BSS PFC at any time via the MODIFY-BSS-PFC PDU, e.g. due to a change in resource availability at the BSS. The BSS sends the MODIFY-BSS-PFC PDU and start timer T8. The SGSN inserts the modified parameters in the MODIFY-BSS-PFC PDU into the relevant PDP contexts. The SGSN shall respond to a modify request with a MODIFY-BSS-PFC-ACK PDU. The Packet Flow Timer (PFT) may be provided to the BSS by the SGSN. This timer is (started or) restarted upon the receipt of the MODIFY-BSS-PFC-ACK PDU and restarted after the transmission of an uplink PDU for that PFC. On receipt of a response to the Modify procedure the BSS shall stop timer T8.
The SGSN can reject the profile proposed by the BSS by answering with a MODIFY-BSS-PFC-ACK PDU containing the previous ABQP.The SGSN may request the modification of the contents of a BSS PFC at any time via the CREATE-BSS-PFC PDU, e.g. due to the activation, modification, or deactivation of a PDP context. It shall not use the MODIFY-BSS-PFC PDU. If the BSS PFC already exists the BSS shall interpret the message as a modification request and the BSS shall reply with a CREATE-BSS-PFC-ACK. The BSS may restrict the requested ABQP given its capabilities and the current load.
8a.2.1 Abnormal conditions
If a MODIFY-BSS-PFC-ACK is not received in response to a MODIFY-BSS-PFC PDU within T8 seconds, then the MODIFY-BSS-PFC PDU shall be repeated a maximum of MODIFY-BSS-PFC-RETRIES attempts. After MODIFY‑BSS-PFC-RETRIES+1 attempts the procedure is stopped and the O&M is informed.
8a.3 Delete BSS PFC procedure
The SGSN may request the deletion of a BSS PFC at any time using the DELETE-BSS-PFC PDU. The BSS shall respond with a DELETE-BSS-PFC-ACK PDU. The BSS may at any time delete a BSS packet flow context without notifying the SGSN.