Manual

Cisco Packet Data Serving Node (PDSN) Release 2.0
Resource Management
18
12.3(11)T
After the PDSN receives the Access-Accept message from AAA, it parses the RADIUS packet and
retrieves the attributes inside it. The PDSN stores the information present in the packet regarding the
quota allocated for the flow and the threshold corresponding to the allocated flow. It also stores the
Quota-ID allocated in the user flow present in the message. Once the flow for the user comes up (IP
address assigned for Simple IP, or MIP RRP received from the HA and sent to the MS), the PDSN starts
metering the user’s traffic over the flow against the allocated quota.
Step 3 User data (IP datagrams) that flow 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 Volume Threshold value reaches 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
HAAA authenticates the RADIUS packet and if authentication 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 the user utilizes. 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 HAAA sends the information received from the Billing Server into a RADIUS Access-Accept
message to be sent to PDSN. The attributes that are encapsulated into a PPAQ VSA include:
– Quota ID
– Allocated quota into VolumeQuota parameter
– Threshold corresponding to the assigned quota into VolumeThreshold parameter.
After the PDSN receives the Access-Accept message from AAA, it parses the RADIUS packet and
retrieves the attributes inside it. The PDSN stores the information present in the packet and updates the
quota allocated for the flow and the current threshold value corresponding to the allocated flow. It also
stores the new Quota-ID allocated for the current quota.
Step 6 User data (IP datagrams) continues to flow through the Prepaid flow, and is accounted in both upstream
and downstream directions. The bytes consumed are checked against the quota allocated for the flow.
Step 7 The PDSN decides to close the prepaid flow based on following criteria:
• Access-Request message was sent to renew the quota and corresponding Access-Accept message
was not received from AAA after a configurable time value. This time is same as the RADIUS
message timeout configured on PDSN.
• An Access-Accept was sent to retrieve quota and before Access-Accept can be received, the
remaining VolumeQuota is consumed. This is when the VolumeQuota value and the
VolumeThreshold values become same.
In this case, PDSN sends an Access-Request message containing the PPAQ VSA that includes:
– Update-Reason Sub-Type to indicate 'Quota reached' (= 4)
– Amount of quota used by the user in VolumeQuota attribute.
At this time, the PDSN marks the prepaid flow as being marked for deleted, such that it does not switch
any packets through it for the prepaid flow. It does not delete the prepaid flow immediately and waits for
the response of the Access-Request or timeout of the Access-Request message.