Manual

Cisco Packet Data Serving Node (PDSN) Release 2.0
Resource Management
22
12.3(11)T
The HAAA encapsulates the prepaid information received for the user from Billing Server in a RADIUS
Access-Accept message and sends it to the PDSN. The RADIUS message includes:
• A PPAQ VSA that contains the following parameters:
– Initialized quota for the user flow specified in VolumeQuota parameter
– Quota ID for the quota allocated
– A threshold value for the quota allocated in VolumeThreshold parameter
• A PTS VSA that contains the following parameters:
– QuotaID as in PPAQ VSA attribute
– TariffSwitchInterval indicating the time in seconds remaining before which the tariff switch
condition will trigger
– TimeIntervalafterTariffSwitchUpdate indicating the duration after tariff switch point when
PDSN will send an on-line Access Request if threshold point is not reached.
• A PPAC VSA indicating prepaid service is based on Volume.
After the PDSN receives the Access-Accept message from AAA, it parses the RADIUS packet and
retrieves the attributes inside it. It stores the information present in the packet regarding the quota
allocated for the flow and threshold corresponding to the allocated flow. The PDSN also stores the
Quota-ID allocated in the user flow present in the message.
Once the flow for the user comes up (the IP address assigned for Simple IP, or MIP RRP received from
the HA and sent to the MS), the PDSN starts metering user's traffic over the flow against the allocated
quota. It also starts the timer corresponding to the value received in TariffSwitchInterval attribute so that
it is aware when the tariff switch condition is hit. The timer is started by the PDSN only if the timestamp
of the Access Request + Tariff Switch Interval is more than the timestamp of the Access Accept message.
QuotaId present in the PTS attribute should be equal to the QuotaId present inside PPAQ. If the 2 values
are unequal, the prepaid flow is closed by PDSN.
Step 3 User data (IP datagrams) that flows through each Prepaid flow is accounted in both upstream and
downstream directions. The bytes consumed are checked against the quota allocated for the flow by the
Billing Server.
Step 4 Once the VolumeThreshold value is reached for the allocated quota for the prepaid flow, the PDSN sends
an Access-Request Message to AAA to refresh quota for the user. This RADIUS packet contains a PPAQ
VSA, which includes following parameters:
• Update-Reason Sub-Type that is set to indicate 'Threshold reached' (= 3)
• Quota ID previously received
• Used volume in the VolumeQuota Sub-Type
The HAAA authorizes the RADIUS packet and if authorization is successful, forwards the
prepaid-related information present in the packet to the Billing Server.
Step 5 The Billing Server updates its database with the amount of quota used by the user. Since the user
indicates quota renewal, the Billing Server apportions a fraction of prepaid account balance of the user.
It also assigns a new Quota ID for the current allocated quota and a corresponding threshold value for
the assigned quota. This information is passed on to HAAA.
The Billing Server also indicates to the HAAA, the time remaining in seconds for the next Tariff Switch
trigger point.