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In usual scenarios, CIoT-enabled UE send data packets infrequently. However, in unusual scenarios, UE can send data packets frequently during a short period resulting in network congestion and affecting services. APN Rate Control is one of the 3GPP standards-compliant mechanisms for rate limiting when UEs send data packets.

APN Rate Control allows Home Public Land Mobile Network (HPLMN) operators to control the amount of user data sent in Downlink (DL) and Uplink (UL). This is done with help of policing the user data on a maximum number of user data packets per time-unit, and/or maximum number of user data octets per time-unit, for both DL and UL.

APN Rate Control policing for DL is done in the P-GW or the SCEF, and the APN Rate Control policing for UL is done in the UE. The P-GW or SCEF can also do APN Rate Control UL policing. For more information on:

• APN Rate Control UL in the UE, see 3GPP TS 24.301.

• APN Rate Control in the SCEF, see 3GPP TS 29.128.

Note	The existing AMBR mechanisms are not suitable for APN Rate Control for CIoT Devices considering radio efficiency and UE battery-life. For example, an AMBR greater than 100 Kbps translates to a potentially large daily data volume.

The P-GW or Service Capability Exposure Function (SCEF) sends an APN Uplink Rate Control command to the UE using the PCO information element (IE). The APN Uplink Rate Control applies to data PDUs sent on that APN by either Data Radio Bearers (S1-U) or Signaling Radio Bearers (NAS Data PDUs). The UE complies with this uplink rate control instruction. The UE considers the rate control instruction as valid until it receives a new one from either P-GW or from SCEF. The P-GW or SCEF enforces the Uplink Rate Control by discarding or delaying packets that exceed the rate as indicated to the UE.

APN Rate Control Indications

APN Rate Control Indication Status is sent as part of Protocol Configuration Options (PCO)/Extended Protocol Configuration Options (ePCO). If P-GW/MME supports the ePCO as part of its capability exchange, the P-GW/S-GW sends the APN Rate Control parameters as part of ePCO. If ePCO is not supported by these entities, the P-GW/S-GW sends the APN Rate Control parameters as part of PCO.

As part of PCO/ePCO, the APN Rate Control parameters are sent as “additional parameters list”. A specific “container identifier” identifies the type of the parameter that is carried in a container. The “container identifier” related to the APN Rate Control are:

• Mobile Station (MS) to network direction:

  • 0016H (APN rate control support indicator)

  • 0019H (Additional APN rate control for exception data support indicator)

• Network to MS direction:

  • 0016H (APN rate control parameters)

  • 0019H (Additional APN rate control for exception data parameters)

When the “container identifier” indicates APN Rate Control support indicator, the “container identifier contents” field is empty and the “length of container identifier contents” indicates a length equal to zero. If the “container identifier contents” field is not empty, it is ignored. This information indicates that the MS supports APN Rate Control functionality.

When the “container identifier” indicates APN Rate Control parameters, the “container identifier contents” field contains parameters for APN Rate Control functionality.

When the “container identifier” indicates Additional APN Rate Control for exception data support indicator, the “container identifier contents” field is empty and the “length of container identifier contents” indicates a length equal to zero. If the “container identifier contents” field is not empty, it is ignored. This information indicates that the MS supports additional APN Rate Control for exception data functionality.

When the “container identifier” indicates Additional APN Rate Control for exception data parameters, the “container identifier contents” field contains parameters for additional APN Rate Control for exception data functionality.

APN Rate Control Status

APN Rate Control Status is the new IE, added as part of Create Session Request (CSReq), Delete Bearer Request (DBReq), and Delete Session Response (DSRes), which holds information of APN Rate Control Value. This IE is encoded as part of CSReq on the UR reattach to denote the P-GW about the remaining limits available for the subscriber on the current timeout period.

P-GW includes this IE when the DBReq is sent only for the default bearer, so that it can be used when the UE is attaching again. In addition, the P-GW includes this IE when the DSRes is sent to MME through S-GW.

Octets 17 to 24 are coded as time in seconds relative to 00:00:00 on 1 January 1900 (calculated as continuous time without leap seconds and traceable to a common time reference) where the binary encoding of the integer part is in the 32 most significant bits, and binary encoding of the fraction part in the 32 least significant bits. The fraction part is expressed with a granularity of 1/2**32 second.

The APN Rate Control Status information is sent by P-GW to MME through S-GW to store the APN Rate control parameters in Mobility Management (MM) context. This helps in restoring the rate control for the same subscriber when it is reestablished again after some time. The parameters are treated as the remaining messages on the remaining time period of the time-unit.

On reestablishment of the same subscriber (on first PDN for the same APN), the MME provides the information back to P-GW in PCO/ePCO. While processing, P-GW considers the values received from MME instead of its local configuration until the first timeout is complete.

Use the following configurations to enable the feature.

configure 
   context context_name 
      apn apn_name 
         iot-rate-control time-unit { unrestricted | mins | hours | days | week } downlink packet-count dl_packet_count uplink packet-count ul_packet_count aer aer_value 
         end 

NOTES:

• time-unit { unrestricted | mins | hours | days | week } : Specifies the mode of time-unit.

• downlink : Applies the APN Rate Control in the downlink direction.

• packet-count dl_packet_count : Specifies the allowed number of downlink packets. The dl_packet_count must be an integer ranging from 0 through 16777215. Integer 0 disables rate control on the downlink direction.

• uplink : Applies the APN Rate Control in the uplink direction.

• packet-count ul_packet_count : Specifies the allowed number of uplink packets. The ul_packet_count must be an integer ranging from 0 through 16777215. Integer 0 disables rate control on the uplink direction.

• aer aer_value : Specifies the number of Additional Exception Reports (AER) in the uplink direction. The aer_value must be an integer ranging from 1 through 65535.

• If previously configured, use the no iot-rate-control CLI command to disable the feature.

This section describes the CLI commands available to monitor and/or troubleshoot the feature.

The following table provides details of the GTPP dictionary available in support of the APN Rate Control for CIoT Devices feature.

The following CDR fields are introduced in the P-GW custom24 GTPP dictionary:

1. Field name: datapacketsFBCDownlink

   • Description: Downlink Packets count

   • Format: Integer

   • CLI command to configure the field: gtpp fbc-downlink-pkt-cnt

   • Default value for field: 0

2. Field name: datapacketsFBCUplink

   • Description: Uplink Packets count

   • Format: Integer

   • CLI command to configure the field: gtpp fbc-uplink-pkt-cnt

   • Default value for field: 0