Binding Migration

A binding migration period is required in order to successfully create new bindings without interfering with existing bindings.

Handling of Binding-capable Session Initiation Requests

This section describes the Policy DRA handling of binding capable session initiation requests during the binding migration period.

For bindings created after PCRF Pooling is enabled, Policy DRA enforces the requirements for handling missing and unconfigured APN values in binding capable session initiation requests.

Policy DRA allows binding-capable session initiation requests for an IMSI that have no APN, or have an unconfigured APN to be routed according to existing bindings for that same IMSI created before PCRF Pooling was enabled.

Note: The software attempts to find a binding created prior to enabling PCRF Pooling. If such a binding is found, it can be used for routing the new request. If no such binding exists, the binding capable session initiation request is rejected.

Upon receipt of a binding-capable session initiation request for an IMSI that has an existing Final binding, the Policy DRA application attempts to route the request to the PCRF from the selected binding. This process is described below.

When checking for an existing binding, the Policy DRA application searches in the following order, using the first binding that matches:

A binding for the IMSI created prior to enabling PCRF Pooling (from the ImsiAnchorKey table)
A binding for the IMSI and APN (from the ImsiApnAnchorKey table)
A binding for the IMSI and suggested PCRF Pool or Sub-Pool (from the ImsiApnAnchorKey table)

Upon receipt of a binding capable session initiation request at a site that has no PCRFs configured, the following requirements apply:

If a binding capable session initiation request is received that would result in a new binding and no PCRFs are configured at the site, Policy DRA shall generate an error response with the 3002 Diameter Response-Code and Error-Message AVP including the string "No PCRFs configured at this site."
Note: This requirement does not apply if a binding already exists for the IMSI and APN, or IMSI and PCRF Pool.
If a binding-capable session initiation request is received and no PCRFs are configured at the site, Policy DRA generates timed alarm 22730, which indicating that no PCRFs are configured.
Note: The alarm is only generated if the binding-capable session initiation request results in a new binding being created.

When routing a binding-capable session initiation request, Policy DRA behaves according to the following requirements:

Upon receipt of a binding-capable session initiation request for an IMSI for which no existing binding is found, a new binding is created using the IMSI, APN, and suggested PCRF Pool or Sub-Pool.
If, when creating the new binding, the record for the IMSI already contains 10 session references, the Policy DRA application generates a Diameter error response using the response code configured for the Policy SBR Error condition.
Note: The Error-Message AVP contains the reason for the failure.
After a binding is successfully created, the Policy DRA application attempts to route the request using the suggested PCRF Pool or Sub-Pool.
When a binding-capable session initiation request results in a new binding, the binding-capable session initiation request is routed to via the Peer Routing Table mapped to the PCRF Pool or Sub-Pool at the site where the request was received.
If the PCRF Pool or Sub-Pool is not mapped to a Peer Routing Table (for example, is mapped to the "-Select-" entry) at the site processing the request, the request is routed according to the routing layer PRT precedence.

Note: When the P-DRA application does not specify a PRT table to use, DRL looks for a PRT in the ingress Peer Node configuration, then, if still not specified, in the Diameter Application-Id configuration. This behavior is necessary for backwards compatibility for cases in which the pre-PCRF Pooling release had the Site Options PRT table for new bindings set to "-Not Selected-".

Binding-capable session initiation requests containing no IMSI are handled accordingly:

If a binding-capable session initiation request is received and the request contains no IMSI, but does contain a configured APN, Policy DRA executes the PCRF Pool selection logic and routes the request using the selected PCRF Pool or Sub-Pool.
Note: A malformed Subscription-Id is treated as if it did not exist. No binding database lookup is attempted here because IMSI is required to do a binding lookup.
If a binding-capable session initiation request is received and the request contains no IMSI, and does not contain an APN, the request is treated as described below:
- Upon receipt of a binding-capable session initiation request containing no Called-Station-Id AVP (for example, no APN), Policy DRA generates and sends a binding capable session initiation answer message using the Result Code configured for the Diameter interface for the "Missing Or Unconfigured APN" condition in the Error Codes GUI. The answer message shall include an Error-Message AVP with the 3-digit error code suffix of 500.
- Upon receipt of a binding-capable session initiation request containing no Called-Station-Id AVP (for example, no APN), Policy DRA asserts Alarm-ID 22730.