Section: 4.7.7.3 APN Rate Control
Content: The APN Rate Control is configured in the PDN GW or in the SCEF. The PDN GW or SCEF can send an APN Uplink Rate Control command to the UE using the PCO information element. The APN Uplink Rate Control applies to data PDUs sent on that APN by either Data Radio Bearers (S1-U) or Signalling Radio Bearers (NAS Data PDUs). The rate control information is separate for uplink and downlink and in the form of: - a positive integer 'number of packets per time unit', and - an indication as to whether or not exception reports can still be sent if this rate control limit has been met, and - if the UE indicated support for it, an integer 'number of additional allowed exception report packets per time unit' once the rate control limit has been reached. UEs supporting APN Rate Control shall support the 'number of additional allowed exception report packets per time unit' and shall provide an indication to the CN at PDN connection establishment. NOTE 1: Pre-Rel-14 UEs do not support the 'number of additional allowed exception report packets per time unit' and do not send an indication to the CN at PDN connection establishment. The UE shall comply with this uplink rate control instruction. If the UE exceeds the uplink 'number of packets per time unit', the UE may still send uplink exception reports if allowed and the 'number of additional allowed exception reports per time unit' has not been exceeded. The UE shall consider this rate control instruction as valid until it receives a new one from either PDN GW or from SCEF. When the last PDN connection using a given APN is released, the APN Rate Control Status (including the number of packets still allowed in the given time unit, the number of additional exception reports still allowed in the given time unit and the termination time of the current APN Rate Control validity period) may be stored in the MME so that it can be retrieved for a subsequent re-establishment of a new first PDN connection for that given APN. At subsequent establishment of a new first PDN connection for that given APN, the PDN GW/SCEF may receive the previously stored APN Rate Control Status and, if the first APN Rate Control validity period has not expired, it applies the received APN Rate Control Status and provides the related parameters to the UE in the PCO (instead of the configured APN Rate Control parameters). If the initially applied parameters differ from the configured APN Rate Control parameters, the PDN GW/SCEF uses the configured APN Rate Control parameters once the first APN Rate Control validity period expires, and sends an update to the UE with the configured APN Rate Control parameters. NOTE 2: The storage of the APN Rate Control Status information for very long time intervals can be implementation specific. The PDN GW or SCEF realises the APN rate control based on a 'maximum allowed rate' per direction. If PDN GW or SCEF provided the 'number of additional allowed exception report packets per time unit' to the UE, then the 'maximum allowed rate' is equal to the 'number of packets per time unit' plus the 'number of additional allowed exception report packets per time unit'. Otherwise, the 'maximum allowed rate' is equal to the 'number of packets per time unit'. NOTE 3: Pre-Rel-14 UEs understand only the 'number of packets per time unit', and, if an indication that exception reports are allowed has been sent to such UEs, there is a risk that exception report packets are discarded by the PDN GW or SCEF. To overcome this problem, the PDN GW or SCEF can still apply a configured 'number of additional allowed exception report packets per time unit' even though not sent to pre-Rel-14 UEs. The PDN GW or SCEF may enforce the uplink rate by discarding or delaying packets that exceed the 'maximum allowed rate'. The PDN GW or SCEF shall enforce the downlink rate by discarding or delaying packets that exceed the downlink part of the 'maximum allowed rate'. NOTE 4: It is assumed that the Serving PLMN Rate is sufficiently high to not interfere with the APN Rate Control as the APN Rate Control, if used, is assumed to allow fewer messages. NAS PDUs related to exception reports are not subject to the Serving PLMN Rate Control.