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Publication Date: 2014-Jul-23
Document File: 7 page(s) / 591K

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DRAs (Diameter Routing Agents) are required to ensure that Gx and Rx data for a subscriber session is handled by the same PCRF site when multiple geo-redundant sites are available. The present disclosure describes methods and systems to eliminate DRAs while continuing to correctly route Gx and Rx data. The PCRF sites are configured to update each other as to which sessions they are currently handling. When a PCRF site receives a request for a session that it is not handling, the site either returns an error message (for an RX request) forcing the subscriber to reconnect to the correct PCRF site; or the site handles the request (for a Gx request) and informs the original PCRF site that the session is being transferred.

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Support for geo-redundant Policy and Charging Rules Function (PCRF) without Diameter Routing Agent (DRA)

4 Mar 2014

INVENTORS Ashid Mohammed

Shilpa Jadav

1. Field of technology and background of the invention

This invention is based on PCRF node in LTE architecture. The invention highlights the concerns of using a PCRF in geo-redundant sites that mandates introduction of a network element DRA; and proposes a proprietary non-standard method to eliminate the dependency. The PCRF related specifications (23.203, 29.212. 29.213, 29.214) could be used as reference.

Figure 1

The architecture diagram above shows only the relevant network elements from 3GPP network for this invention.

PGEF or P-GW or GSSN: It provides connectivity from the UE to external packet data networks by being the point of exit and entry of traffic for the UE. A UE may have simultaneous connectivity with more than one PGW for accessing multiple PDNs. It is connected to the PCRF or the DRA (if it exists) by Gx interface.

P-CSCF or AF: Proxy Call Session Control Function is a SIP proxy that is the first point of contact for the IMS terminal. The UE attaches to the P-CSCF prior to performing IMS registrations and initiating SIP sessions. It sits on the path of all signalling, and can inspect every signal, provides subscriber authentication and ensures that the IMS terminals do not misbehave. It is connected to PCRF or DRA (if it exists) by Rx interface.

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DRA: Diameter Routing Agent ensures that all Diameter sessions established over the Gx, Gxx, Rx and for unsolicited application reporting, reach the same PCRF when multiple and separately addressable PCRFs have been deployed in a Diameter realm. DRA is not required in a network that deploys a single PCRF per Diameter realm.

PCRF: Policy and Charging Rule Function is the software node designated in real-time to determine policy rules in a multimedia network. It operates at the network core and accesses subscriber database and other specialized functions, such as a charging system, in a centralized manner. If a VoLTE user needs better quality of service then it is the responsibility of PCRF to initiate

2. Problem

Assume geo-redundant PCRF farms - referred to below as Policy Control Server (PCS) Farms A and
B. For simplicity, assume only 1 P-GW/GGSN (say GGSN-A) and 1 AF (Application Function, e.g. P- CSCF) connected to the Farm A and B. The GGSN has a primary Gx connection with farm A and Secondary (backup) Gx connection with farm B. The AF, similarly has a primary Rx connection with farm A and Secondary (backup) Rx connection with farm B. Only in event of an issue with the Gx or Rx primary link, the secondary connection is used.

Figure 1

Assume a scenario, where the primary Rx link is down (can happen due to issues to PCRF dispatcher, load balancer (LB) issues, network issues, etc). In this case the AF would route all Rx messages to the secondary configured geo-redundant farm...