PCRF Sub-Pool Selection Rules

The PCRF Sub-Pool Selection table contains rules for selection of a PCRF Sub-Pool for a given PCRF Pool and Origin-Host value.

It is sometimes necessary to subdivide a PCRF Pool into sub-pools (such as a need to support controlled routing of traffic to a new PCRF). In such a case, you can configure PCRF Sub-Pool Selection Rules to a selected a sub-pool on the basis of the Origin-Host of the binding capable session initiation request.

A PCRF Sub-Pool Selection Rule has certain attributes:

• The Default PCRF Pool can have sub-pools.
• The PCRF Pool Name column contains hyperlinks to the PCRF Pools screen filtered by the PCRF Pool Name.
• Origin-Host is the only supported PCRF Sub-Pool Selection parameter.
• Supported Origin-Host operators are: Equals, Starts With, and Ends With.
• Priority values can range from 1 to 99, with 1 being the highest priority.

An APN-to-PCRF Pool mapping specifies that all binding-capable session initiation requests that result in creation of a new binding should be routed to a PCRF in PCRF Pool X.

A PCRF Sub-Pool Selection Rule can override the APN-to-PCRF Pool mapping by specifying binding-capable session initiation requests that result in new bindings that were destined for PCRF Pool X, but come from PCEF Y, should be routed to a PCRF in PCRF Sub-Pool Z.

A PCRF Sub-Pool Selection Rule will never be considered if no APN is mapped to its PCRF Pool. As a result, it is safe to add PCRF Sub-Pool Selection Rules prior to mapping APNs to the PCRF Pool that is being subdivided. It is also acceptable to add PCRF Sub-Pool Selection Rules for a PCRF Pool that is already mapped to an APN. However, if this is done, bindings that were created prior to the existence of the PCRF Sub-Pool Selection Rule take precedence over the PCRF Sub-Pool chosen for new binding-capable session initiation requests that arrive after the new rule is in place. This behavior is necessary to prevent split bindings.

PCRF Sub-Pool Selection Rules are configured using the NOAMP GUI as a network-wide managed object.

The creation of a new PCRF Sub-Pool Selection Rule does not affect P-DRA signaling in any way until a pair of conditions exist:

• An APN is mapped to the PCRF Pool using the Access Point Names screen.
• A binding-capable session initiation request arrives with an APN mapped to that PCRF Pool and an Origin-Host that matches the Condition specified in the PCRF Sub-Pool Selection Rule.

When a PCRF Sub-Pool Selection Rule entry is added, new bindings from that APN and Origin-Host will be routed to a PCRF in the specified PCRF Sub-Pool. When a PCRF Sub-Pool Selection Rule is mapped to a PCRF Sub-Pool, a check is performed to determine if the selected PCRF Sub-Pool is configured with a PRT mapping at each site. If at least one site does not have a mapping for the selected PCRF Sub-Pool, a confirmation dialog is displayed that including a warning:

• If a site does not have the PCRF Sub-Pool mapped to a PRT table, a confirmation dialog is displayed on the APN GUI warning that Site X does not have a mapping defined for this PCRF Sub-Pool. You can choose to continue, but with the knowledge that a call might fail at that site if a binding-capable session initiation request arrives with an APN and Origin-Host that is mapped to that PCRF Sub-Pool.
• If a site cannot be reached due to network errors, a confirmation dialog is displayed on to warn you that it cannot be determined whether Site X has a mapping defined for this PCRF Sub-Pool. You can choose to continue, but with the knowledge that a call might fail at that site if a binding-capable session initiation request arrives with an APN and Origin-Host that is mapped to that PCRF Pool.

The PCRF Sub-Pool Selection Rule GUI prevents creation of rules that are:

• Ambiguous
• Conflicting
• Duplicate

Two rules are considered as ambiguous if certain criteria are met:

• The rules have the same PCRF Pool values and
• The rules have the same Priority values and
• The rules have different PCRF Sub-Pool values and one of several conditions is true:
  • One rule has an Origin-Host with a Starts With operator and the other rule has an Origin-Host with an Ends With operator -- OR –
    • For example, starts With ab and Ends With xyz
    • Value length is not considered as a factor in the best match decision at this time.
  • Both rules have an Origin-Host with a Starts With operator and all of the value characters of the shorter value match the first characters of the longer value -- OR –
    • For example, starts With abc and Starts With ab
  • Both rules have an Origin-Host with a Ends With operator and all of the value characters of the shorter value match the last characters of the longer value.
    • For examples, ends With xyz and Ends With yz

Two rules are considered to be conflicting if all of the criteria are met:

• The rules have the same PCRF Pool values.
• The rules have the same Priority values.
• The rules have the same Origin-Host operators and values.
• The rules have different PCRF Sub-Pool values.

Two rules are considered to be duplicate if all of the criteria are met:

• The rules have the same PCRF Pool values.
• The rules have the same Origin-Host operators and values.
• The rules have the same PCRF Sub-Pool values.