# US 11,910,474 B1 · IMS selection for multi-HSS route advance

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- Number: US 11,910,474 B1
- Document ID: US11910474B1
- Status: Granted
- Kind: B1
- Application number: 17/189,880
- Filed: 2021-03-02
- Granted: 2024-02-20
- Earliest claimed: 2021-03-02
- Assignees: T-Mobile USA, Inc.
- Applicants: T-Mobile USA, Inc.
- Inventors: Saqib Badar; Shujaur Mufti
- Web page: https://patentgrep.com/patent/US11910474B1

## CPC

- H04W 8/04: Registration at HLR or HSS [Home Subscriber Server]
- H04L 61/4511: using domain name system [DNS]
- H04L 61/4588: containing mobile subscriber information, e.g. home subscriber server [HSS]
- H04L 65/1016: IP multimedia subsystem [IMS]
- H04L 65/1045: Proxies, e.g. for session initiation protocol [SIP]
- H04L 65/1073: Registration or de-registration
- H04L 65/1104: Session initiation protocol [SIP]
- H04W 8/24: Transfer of terminal data
- H04W 60/005: {Multiple registrations, e.g. multihoming}
- H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72)
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## Abstract

In a multi-HSS domain, in which some HSSs support a custom route advance (RA) logic and others do not, a P-CSCF may receive a request for service from a UE associated with one of the HSSs, and send the request to an assigned S-CSCF (S-CSCF1) associated with the UE. Upon failing to receive a response from the S-CSCF1 within a preset time period, the P-CSCF may send the request to the I-CSCF. Based on information included in the request, the I-CSCF may discover an address of a second S-CSCF (S-CSCF2) from the associated HSS and sending the request to the S-CSCF2 based on the discovered address of the S-CSCF2, or send a message indicative of the requested service being unavailable to the P-CSCF.

## Claims

### Claim 1

A method comprising:
receiving, by a proxy call session control function (P-CSCF), a request for service from a user equipment (UE) associated with a home subscriber server (HSS) of a plurality of HSSs;
sending, by the P-CSCF, the request to an assigned serving CSCF (S-CSCF1) associated with the UE;
upon failing to receive, by the P-CSCF, a response from the S-CSCF1 within a preset time period, sending the request to an interrogating CSCF (I-CSCF); and
based on information included in the request, performing, by the I-CSCF, one of:
discovering an address of a second S-CSCF (S-CSCF2) from the associated HSS and sending the request to the S-CSCF2 based on the discovered address of the S-CSCF2, or
sending, to the P-CSCF, a message indicative of the requested service being unavailable,
wherein the information indicates whether the HSS associated with the UE supports custom route advance (RA) logic, and the I-CSCF performs the discovering when the HSS supports the custom RA logic and performs the sending when the HSS does not support the custom RA logic.

### Claim 2 (depends on 1)

The method of claim 1, wherein discovering, by the I-CSCF, the address of the S-CSCF2 from the associated HSS comprises:
determining that the information included in the request comprises a RA flag;
determining that a feature tag associated with the request is consistent with the custom RA logic, the custom RA logic being associated with the RA flag; and
initiating a location-info-request (LIR) and a location-info-answer (LIA) messages between the I-CSCF and the associated HSS based on the custom RA logic associated with the RA flag.

### Claim 3 (depends on 2)

The method of claim 2, wherein:
the LIA message includes a request for registration and capabilities and a reassignment pending flag, and
the LIR message includes mandatory capabilities associated with the UE.

### Claim 4 (depends on 3)

The method of claim 3, wherein discovering the address of the S-CSCF2 from the associated HSS comprises:
providing, by the associated HSS, address information of the S-CSCF2 as the mandatory capabilities.

### Claim 5 (depends on 4)

The method of claim 4, wherein the address of the S-CSCF2 comprises a full qualified domain name (FQDN) associated with the S-CSCF2.

### Claim 6 (depends on 5)

The method of claim 5, wherein discovering the address of the S-CSCF2 comprises:
performing, by the I-CSCF, an FQDN resolution based on the mandatory capabilities to determine the S-CSCF2.

### Claim 7 (depends on 2)

The method of claim 2, wherein the feature tag indicates the custom RA logic per one of:
SIP method,
access type,
service type, or
Cx realm.

### Claim 8 (depends on 1)

The method of claim 1, wherein the information included in the request, based on which the I-CSCF sends to the P-CSCF the message indicative of the requested service being unavailable, includes at least one of:
the information lacking a RA flag, or
a feature tag associated with the request.

### Claim 9 (depends on 1)

The method of claim 1, wherein the HSS associated with the UE not supporting the custom RA logic is based on:
initiating, by the I-CSCF, a location-info-request (LIR) and a location-info-answer (LIA) messages between the I-CSCF and the associated HSS; and
receiving, by the I-CSCF from the associated HSS, address information of the S-CSCF1 as the assigned S-SCSF.

### Claim 10

A computing system comprising:
one or more processors; and
one or more non-transitory computer-readable media storing computer-executable instructions that, when executed by the one or more processors, cause the one or more processors to perform actions comprising:
receiving, by a proxy call session control function (P-CSCF), a request for service from a user equipment (UE) associated with a home subscriber server (HSS) of a plurality of HSSs;
sending, by the P-CSCF, the request to an assigned serving CSCF (S-CSCF1) associated with the UE;
upon failing to receive, by the P-CSCF, a response from the S-CSCF1 within a preset time period, sending the request to an interrogating CSCF (I-CSCF); and
based on information included in the request, performing, by the I-CSCF, one of:
discovering an address of a second S-CSCF (S-CSCF2) from the associated HSS and sending the request to the S-CSCF2 based on the discovered address of the S-CSCF2, or
sending, to the P-CSCF, a message indicative of the requested service being unavailable,
wherein the information indicates whether the HSS associated with the UE supports custom route advance (RA) logic, and the I-CSCF performs the discovering when the HSS supports the custom RA logic and performs the sending when the HSS does not support the custom RA logic.

### Claim 11 (depends on 10)

The computing system of claim 10, wherein discovering, by the I-CSCF, the address of the S-CSCF2 from the associated HSS comprises:
determining that the information included in the request comprises a RA route flag;
determining that a feature tag associated with the request is consistent with the custom RA logic associated with the RA flag; and
initiating a location-info-request (LIR) and a location-info-answer (LIA) messages between the I-CSCF and the associated HSS based on the custom RA logic, the custom RA logic being associated with the RA flag.

### Claim 12 (depends on 11)

The computing system of claim 11, wherein:
the LIA message includes a request for registration and capabilities and a reassignment pending flag, and
the LIR message includes mandatory capabilities associated with the UE.

### Claim 13 (depends on 12)

The computing system of claim 12, wherein discovering the address of the S-CSCF2 from the associated HSS comprises:
providing, by the associated HSS, address information of the S-CSCF2 as the mandatory capabilities.

### Claim 14 (depends on 13)

The computing system of claim 13, wherein:
the address of the S-CSCF2 comprises a full qualified domain name (FQDN) associated with the S-CSCF2, and
discovering the address of the S-CSCF2 comprises performing, by the I-CSCF, an FQDN resolution based on the mandatory capabilities to determine the S-CSCF2.

### Claim 15 (depends on 11)

The computing system of claim 11, wherein the feature tag indicates the custom RA logic per one of:
SIP method,
access type,
service type, or
Cx realm.

### Claim 16

One or more non-transitory computer-readable media storing computer-executable instructions that, when executed by one or more processors, cause the one or more processors to perform actions comprising:
receiving, by a proxy call session control function (P-CSCF), a request for service from a user equipment (UE) associated with a home subscriber server (HSS) of a plurality of HSSs;
sending, by the P-CSCF, the request to a first serving CSCF (S-CSCF1) associated with the UE;
upon failing to receive, by the P-CSCF, a response from the S-CSCF1 within a preset time period, sending the request to an interrogating CSCF (I-CSCF); and
based on information included in the request, performing, by the I-CSCF, one of:
discovering an address of a second S-CSCF (S-CSCF2) from the associated HSS and sending the request to the S-CSCF2 based on the discovered address of the S-CSCF2, or
sending, to the P-CSCF, a message indicative of the requested service being unavailable,
wherein the information indicates whether the HSS associated with the UE supports custom route advance (RA) logic, and the I-CSCF performs the discovering when the HSS supports the custom RA logic and performs the sending when the HSS does not support the custom RA logic.

### Claim 17 (depends on 16)

The one or more non-transitory computer-readable media of claim 16, wherein discovering, by the I-CSCF, the address of the S-CSCF2 from the associated HSS comprises:
determining that the information included in the request comprises a RA flag;
determining that a feature tag associated with the request is consistent with the custom RA logic, the custom RA logic being associated with the RA flag; and
initiating a location-info-request (LIR) and a location-info-answer (LIA) messages between the I-CSCF and the associated HSS based on the custom RA logic associated with the RA flag.

### Claim 18 (depends on 17)

The one or more non-transitory computer-readable media of claim 17, wherein:
the LIA message includes a request for registration and capabilities and a reassignment pending flag, and
the LIR message includes mandatory capabilities associated with the UE.

### Claim 19 (depends on 18)

The one or more non-transitory computer-readable media of claim 18, wherein:
the address of the S-CSCF2 comprises a full qualified domain name (FQDN) associated with the S-CSCF2, and
discovering the address of the S-CSCF2 comprises performing, by the I-CSCF, an FQDN resolution based on the mandatory capabilities to determine the S-CSCF2.

### Claim 20 (depends on 17)

The one or more non-transitory computer-readable media of claim 17, wherein the feature tag indicates the custom RA logic per one of:
SIP method,
access type,
service type, or
Cx realm.