# US 11,121,911 B2 · System and method to facilitate network element failure detection and session restoration in a network environment > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,121,911 B2 - Document ID: US11121911B2 - Status: Granted - Kind: B2 - Application number: 16/359,847 - Filed: 2019-03-20 - Published: 2019-07-18 - Granted: 2021-09-14 - Earliest claimed: 2017-02-19 - Assignees: Cisco Technology, Inc. - Applicants: Cisco Technology, Inc. - Inventors: Konstantin Livanos; Ian McDowell Campbell; Charles C. Wolfinger - Web page: https://patentgrep.com/patent/US11121911B2 ## CPC - H04L 41/0668: by dynamic selection of recovery network elements, e.g. replacement by the most appropriate element after failure - H04L 12/1407: {Policy-and-charging control [PCC] architecture} - H04L 43/0805: by checking availability - H04L 43/0817: by checking functioning - H04M 15/00: Arrangements for metering, time-control or time indication {; Metering, charging or billing arrangements for voice wireline or wireless communications, e.g. VoIP} - H04M 15/57: {for integrated multimedia messaging subsystem [IMS]} - H04M 15/66: {Policy and charging system} - H04M 15/8228: {Session based} - H04W 4/24: Accounting or billing - H04W 24/04: Arrangements for maintaining operational condition - H04L 41/046: comprising network management agents or mobile agents therefor - H04L 61/503: using an authentication, authorisation and accounting [AAA] protocol, e.g. remote authentication dial-in user service [RADIUS] or Diameter - H04W 88/16: Gateway arrangements - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - H04M: TELEPHONIC COMMUNICATION (circuits for controlling other apparatus via a telephone cable and not involving telephone switching apparatus G08) - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) ## Abstract A method is provided in one example embodiment and may include maintaining, by a Diameter Routing Agent (DRA), an availability status for a plurality of network elements; receiving a request associated with a user equipment (UE) session, wherein a first network element of the plurality of network elements is serving the UE session; determining that the first network element serving the UE session is unavailable; and re-establishing the UE session at a second network element of the plurality of network elements that is available, wherein the re-establishing is performed without terminating the UE session. ## Claims ### Claim 1 A method comprising: maintaining, by a Diameter Routing Agent (DRA), an availability status for a plurality of Policy and Charging Rules Functions (PCRFs); receiving a request associated with a user equipment (UE) session, wherein a first PCRF of the plurality of PCRFs is serving the UE session; determining that the first PCRF serving the UE session is unavailable; and re-establishing the UE session at a second PCRF of the plurality of PCRFs that is available, wherein the re-establishing is performed without terminating the UE session, comprising: transmitting from the DRA to a Packet Data Network (PDN) Gateway (PGW) a request comprising a first session identifier identifying a first session between the UE and the first PCRF; receiving at the DRA a response from the PGW comprising a second session identifier identifying a second session between the UE and the second PCRF, wherein the first session identifier is different than the second session identifier; and transmitting to the second PCRF a message comprising the second session identifier. ### Claim 2 (depends on 1) The method of claim 1, wherein the request is at least one of: an initial Credit-Control-Request (CCR-I) message received by the DRA via a Gx interface; an update Credit-Control-Request (CCR-U) message received by the DRA via a Gx interface; an initial Credit-Control-Request (CCR-I) message received by the DRA via an Sd interface; an Authorization-and-Authentication-Request (AAR) message received by the DRA via an Rx interface; and a TDF-Session-Request (TSR) message received by the DRA via an Sd interface. ### Claim 3 (depends on 1) The method of claim 1, wherein the determining further comprises: determining a respective availability status for each respective PCRF of the plurality of PCRFs based on a determination that the first PCRF serving the UE session is unavailable; and selecting the second PCRF to serve the UE session based, at least in part, on the respective availability status of the second PCRF indicating that it is available. ### Claim 4 (depends on 1) The method of claim 1, wherein the request comprises a Gx Re-Authorization-Request (RAR) message and the PGW serves the UE session. ### Claim 5 (depends on 1) The method of claim 1, wherein the request is a TDF-Session-Request (TSR) message received by the DRA from PCRF. ### Claim 6 (depends on 1) The method of claim 1, wherein the PGW is configured to generate the second session identifier in response to receiving the request from the DRA. ### Claim 7 (depends on 4) The method of claim 4, wherein the message comprising the second session identifier comprises an initial Credit-Control-Request (CCR-I) message. ### Claim 8 (depends on 5) The method of claim 5, further comprising: causing packets for the UE session to be buffered at the PGW until an indication is received at the PGW indicating that the PGW is to forward the packets to the second PCRF. ### Claim 9 One or more non-transitory tangible media encoding logic that includes instructions for execution by a processor, wherein the execution causes the processor to perform operations comprising: maintaining, by a Diameter Routing Agent (DRA), an availability status for a plurality of Policy and Charging Rules Functions (PCRFs); receiving a request associated with a user equipment (UE) session, wherein a first PCRF of the plurality of PCRFs is serving the UE session; determining that the first PCRF serving the UE session is unavailable; and re-establishing the UE session at a second PCRF of the plurality of PCRFs that is available, wherein the re-establishing is performed without terminating the UE session, comprising: transmitting from the DRA to a Packet Data Network (PDN) Gateway (PGW) a request comprising a first session identifier identifying a first session between the UE and the first PCRF; receiving at the DRA a response from the PGW comprising a second session identifier identifying a second session between the UE and the second PCRF, wherein the first session identifier is different than the second session identifier; and transmitting to the second PCRF a message comprising the second session identifier. ### Claim 10 (depends on 9) The media of claim 9, wherein the request is at least one of: an initial Credit-Control-Request (CCR-I) message received by the DRA via a Gx interface; an update Credit-Control-Request (CCR-U) message received by the DRA via a Gx interface; an initial Credit-Control-Request (CCR-I) message received by the DRA via an Sd interface; an Authorization-and-Authentication-Request (AAR) message received by the DRA via an Rx interface; and a TDF-Session-Request (TSR) message received by the DRA via an Sd interface. ### Claim 11 (depends on 9) The media of claim 9, wherein the determining further comprise: determining a respective availability status for each respective PCRF of the plurality of PCRFs based on a determination that the first PCRF serving the UE session is unavailable; and selecting the second PCRF to serve the UE session based, at least in part, on the respective availability status of the second PCRF indicating that it is available. ### Claim 12 (depends on 9) The media of claim 9, wherein the request comprises a Gx Re-Authorization-Request (RAR) message, the PGW serves the UE session, and the message comprising the second session identifier comprises an initial Credit-Control-Request (CCR-I) message. ### Claim 13 (depends on 9) The media of claim 9, wherein the request is a TDF-Session-Request (TSR) message received by the DRA from a PCRF. ### Claim 14 (depends on 9) The media of claim 9, wherein the PGW is configured to generate the second session identifier in response to receiving the request from the DRA. ### Claim 15 (depends on 13) The media of claim 13, wherein the execution causes the processor to perform further operations comprising: causing packets for the UE session to be buffered at the PGW until an indication is received at the PGW indicating that the PGW is to forward the packets to the second PCRF. ### Claim 16 A Diameter Routing Agent comprising: at least one memory element for storing data; and at least one processor to execute instructions associated with the data, wherein executing the instructions causes the Diameter Routing Agent (DRA) to perform operations comprising: maintaining, by the DRA, an availability status for a plurality of Policy and Charging Rules Functions (PCRFs); receiving a request associated with a user equipment (UE) session, wherein a first PCRF of the plurality of PCRFs is serving the UE session; determining that the first PCRF serving the UE session is unavailable; and re-establishing the UE session at a second PCRF of the plurality of PCRFs that is available, wherein the re-establishing is performed without terminating the UE session, comprising: transmitting from the DRA to a Packet Data Network (PDN) Gateway (PGW) a request comprising a first session identifier identifying a first session between the UE and the first PCRF; receiving at the DRA a response from the PGW comprising a second session identifier identifying a second session between the UE and the second PCRF, wherein the first session identifier is different than the second session identifier; and transmitting to the second PCRF a message comprising the second session identifier. ### Claim 17 (depends on 16) The Diameter Routing Agent of claim 16, wherein the request is at least one of: an initial Credit-Control-Request (CCR-I) message received by the DRA via a Gx interface; an update Credit-Control-Request (CCR-U) message received by the DRA via a Gx interface; an initial Credit-Control-Request (CCR-I) message received by the DRA via an Sd interface; an Authorization-and-Authentication-Request (AAR) message received by the DRA via an Rx interface; and a TDF-Session-Request (TSR) message received by the DRA via an Sd interface. ### Claim 18 (depends on 16) The Diameter Routing Agent of claim 16, wherein the determining further comprises: determining a respective availability status for each respective PCRF of the plurality of PCRFs based on a determination that the first PCRF serving the UE session is unavailable; and selecting the second PCRF to serve the UE session based, at least in part, on the respective availability status of the second PCRF indicating that it is available. ### Claim 19 (depends on 16) The Diameter Routing Agent of claim 16, wherein the request comprises a Gx Re-Authorization-Request (RAR) message and the PGW serves the UE session. ### Claim 20 (depends on 16) The Diameter Routing Agent of claim 16, wherein the PGW is configured to generate the second session identifier in response to receiving the request from the DRA.