FORM 2
THE PATENTS ACT, 1970 (39 OF 1970) & THE PATENT RULES, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
“METHOD AND SYSTEM FOR TRAFFIC MIGRATION FROM DR SITE TO PR SITE IN S-CSCF”
We, Jio Platforms Limited, an Indian National, of Office - 101, Saffron, Nr. Centre Point, Panchwati 5 Rasta, Ambawadi, Ahmedabad - 380006, Gujarat, India.
The following specification particularly describes the invention and the manner in which it is to be performed.

METHOD AND SYSTEM FOR TRAFFIC MIGRATION FROM DR SITE
TO PR SITE IN S-CSCF
FIELD OF DISCLOSURE
[0001] Embodiments of the present disclosure generally relate to network performance management systems. More particularly, embodiments of the present disclosure relate to system and method for traffic migration from a disaster recovery (DR) site to a primary recovery (PR) site in a Serving Call Session Control Function (S-CSCF).
BACKGROUND
[0002] Wireless communication technology has rapidly evolved over the past few decades, with each generation bringing significant improvements and advancements. The first generation of wireless communication technology was based on analog technology and offered only voice services. However, with the advent of the second-generation (2G) technology, digital communication and data services became possible, and text messaging was introduced. The third-generation (3G) technology marked the introduction of high-speed internet access, mobile video calling, and location-based services. The fourth-generation (4G) technology revolutionized wireless communication with faster data speeds, better network coverage, and improved security. Currently, the fifth-generation (5G) technology is being deployed, promising even faster data speeds, low latency, and the ability to connect multiple devices simultaneously. With each generation, wireless communication technology has become more advanced, sophisticated, and capable of delivering more services to its users.
[0003] The migration from Disaster Recovery (DR) site to Primary Recovery (PR) site in the Serving Call/Session Control Function (S-CSCF) in a 4G/5G network have certain drawbacks in the existing solutions.

[0004] In the current existing solutions, the migration process from DR to PR can be complex and time-consuming. It requires careful planning, coordination, and testing to ensure a smooth transition. The configuration changes, protocol adaptations, and interoperability testing involved can increase the complexity of the migration. Further, the migration process requires network resources as devices will be forcefully de-registered. This can result in increased resource utilization. Also, during the migration process, there is a possibility of service disruptions or downtime. It is crucial to carefully plan and execute the migration to minimize any negative impact on ongoing services and end-user experience. While migrating from DR to PR in the S-CSCF can offer benefits like improved scalability, simplified network architecture, and reduced signaling load, it is crucial to carefully assess and mitigate the potential disadvantages to ensure a successful migration. Further, over the period of time various solutions have been developed to improve the performance of communication devices and for seamless traffic migration from DR to PR in SIB node. However, there are certain challenges with existing solutions.
[0005] Thus, there exists an imperative need in the art to provide system and method for seamless traffic migration from a disaster recovery (DR) site to a primary recovery (PR) site in a Serving Call Session Control Function (S-CSCF).
SUMMARY
[0006] This section is provided to introduce certain aspects of the present disclosure in a simplified form that are further described below in the detailed description. This summary is not intended to identify the key features or the scope of the claimed subject matter.
[0007] An aspect of the present disclosure may relate to a method for traffic migration from a disaster recovery (DR) site to a primary recovery (PR) site in a

Serving Call Session Control Function (S-CSCF) in a 4G/5G network, the method comprising receiving, by a transceiver unit, at an interrogating call session control function (I-CSCF) unit, a signal to initiate migration. The method further comprises sending, by the transceiver unit, from the I-CSCF unit, a user authentication request (UAR) to a home subscriber server (HSS) to obtain a server name. The method further comprises obtaining, by a fetching unit, at the I-CSCF unit, the server name from the HSS through a User Authorization Answer (UAA). The method further comprises verifying, by a verification unit, at the I-CSCF unit, whether a forceful selection mode is ON, and if the obtained server name corresponds to a DR site. The method further comprises initiating, by an initial unit, from the I-CSCF unit, a protocol for traffic migration to the PR site based on determining that the obtained server name is of the DR site and forceful selection is in an ON state. Thereafter, the method further comprises sending, by the transceiver unit, at the I-CSCF unit, the UAR with capabilities option to the HSS to facilitate selection of the PR site S-CSCF.
[0008] In an exemplary aspect of the present disclosure, the traffic migration is supported by a System Integration Bus (SIB) node.
[0009] In an exemplary aspect of the present disclosure, the server name is Disaster Recovery Serving Call Session Control Function (DR S-CSCF) unit.
[0010] In an exemplary aspect of the present disclosure, the UAR with capabilities option is sent to the HSS to facilitate high priority-based selection of the PR site S-CSCF.
[0011] In an exemplary aspect of the present disclosure, the method further comprises receiving, via the transceiver unit, by the DR S-CSCF unit, a REGISTER request from the I-CSCF unit. The method further comprises clearing, via a clarification unit, by the DR S-CSCF unit, a subscriber data in response to the

REGISTER request. The method further comprises responding, via the transceiver unit, by the DR S-CSCF unit, with a 480 signal to the I-CSCF unit.
[0012] In an exemplary aspect of the present disclosure, the I-CSCF unit, upon receiving the 480 signal, triggers an S-CSCF restoration.
[0013] In an exemplary aspect of the present disclosure, the ALWAYS option, the I-CSCF unit queries the HSS through the UAR and receive UAA to obtain the server name corresponding to the DR S-CSCF unit, and in response to the forceful selection being ON and the server name being from the DR site, sends the UAR with the capabilities option.
[0014] In an exemplary aspect of the present disclosure, the capabilities option comprises at least one of a support for high-definition voice service, a video call functionality, and an enhanced data security feature for determining whether the S-CSCF supports at least one service from an emergency call, session timer, or a media type.
[0015] Another aspect of the present disclosure may relate to a system for traffic migration from a disaster recovery (DR) site to a primary recovery (PR) site in a Serving Call Session Control Function (S-CSCF) in a 4G/5G network, the system comprises a transceiver unit configured to receive, at an interrogating call session control function (I-CSCF) unit, a signal to initiate migration; and send from the I_CSCF unit, a user authentication request (UAR) to a home subscriber server (HSS) to obtain a server name. The system comprises a fetching unit connected to at least the transceiver unit, wherein the fetching unit is configured to obtain, at the I-CSCF unit, the server name from the HSS through a User Authorization Answer (UAA). The system further comprises a verification unit connected to at least the fetching unit, wherein the verification unit is configured to verify at the I-CSCF unit, whether a forceful selection mode is ON, and if the obtained server name corresponds to a DR site. The system comprises an initiating unit connected to at

least the verification unit, wherein the initiating unit is configured to initiate, from the I-CSCF unit, a protocol for traffic migration the transceiver unit is connected to at least the initial unit, wherein the transceiver unit is configured to send, at the I-CSCF, the UAR with capabilities option to the HSS to facilitate selection of the PR site S-CSCF.
[0016] Yet another aspect of the present disclosure may relate to a non-transitory computer readable storage medium storing instructions for traffic migration from a disaster recovery (DR) site to a primary recovery (PR) site in a Serving Call Session Control Function (S-CSCF) in a 4G/5G network the instructions include executable code which, when executed by a one or more units of a system, causes: a transceiver unit of the system to receive, at an interrogating call session control function (I-CSCF) unit, a signal to initiate migration; send from the I_CSCF unit, a user authentication request (UAR) to a home subscriber server (HSS) to obtain a server name; a fetching unit of the system to obtain, at the I-CSCF unit, the server name from the HSS through a User Authorization Answer (UAA); a verification unit of the system to verify at the I-CSCF unit, whether a forceful selection mode is ON, and if the obtained server name corresponds to a DR site; based on determining that the obtained server name is of the DR site and forceful selection is in an ON state, an initial unit of the system to initiating, from the I-CSCF unit, a protocol for traffic migration the transceiver unit of the system to send, at the I-CSCF, the UAR with capabilities option to the HSS to facilitate selection of the PR site S-CSCF.
OBJECTS OF THE DISCLOSURE
[0017] Some of the objects of the present disclosure, which at least one embodiment disclosed herein satisfies are listed herein below.
[0018] Some of the objects of the present disclosure, which at least one embodiment disclosed herein satisfies are listed herein below.

[0019] It is an object of the present disclosure to provide a system and a method enable seamless traffic migration from DR to PR.
[0020] It is another object of the present disclosure to provide a solution that the enhances user experience even in unforeseen circumstances.
[0021] It is yet another object of the present disclosure to provide a solution to ensure efficient use of network resources.
DESCRIPTION OF THE DRAWINGS
[0022] The accompanying drawings, which are incorporated herein, and
constitute a part of this disclosure, illustrate exemplary embodiments of the disclosed methods and systems in which like reference numerals refer to the same parts throughout the different drawings. Components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Also, the embodiments shown in the figures are not to be construed as limiting the disclosure, but the possible variants of the method and system according to the disclosure are illustrated herein to highlight the advantages of the disclosure. It will be appreciated by those skilled in the art that disclosure of such drawings includes disclosure of electrical components or circuitry commonly used to implement such components.
[0023] FIG. 1 illustrates an exemplary block diagram representation of 5th generation core (5GC) network architecture;
[0024] FIG. 2 illustrates an exemplary block diagram of a computing device upon which the features of the present disclosure may be implemented in accordance with exemplary implementation of the present disclosure;

[0025] FIG. 3 illustrates an exemplary block diagram of a system for traffic migration from a disaster recovery (DR) site to a primary recovery (PR) site in a Serving Call Session Control Function (S-CSCF) in a 4G/5G network, in accordance with exemplary implementations of the present disclosure;
[0026] FIG. 4 illustrates an exemplary block diagram of a method flow diagram for traffic migration from a disaster recovery (DR) site to a primary recovery (PR) site in a Serving Call Session Control Function (S-CSCF) in a 4G/5G network, in accordance with exemplary implementations of the present disclosure;
[0027] FIG. 5A illustrates an exemplary sequence diagram indicating SCSCF Re-Selection-Always Option for traffic migration from a disaster recovery (DR) site to a primary recovery (PR) site in a Serving Call Session Control Function (S-CSCF) in a 4G/5G network, in accordance with exemplary implementations of the present disclosure.; and
[0028] FIG. 5B illustrates an exemplary sequence diagram indicating SCSCF Re-Selection-SCSCF-INITIATED Option for traffic migration from a disaster recovery (DR) site to a primary recovery (PR) site in a Serving Call Session Control Function (S-CSCF) in a 4G/5G network, in accordance with exemplary implementations of the present disclosure.
[0029] The foregoing shall be more apparent from the following more detailed description of the disclosure.
DETAILED DESCRIPTION
[0030] In the following description, for the purposes of explanation, various specific details are set forth in order to provide a thorough understanding of embodiments of the present disclosure. It will be apparent, however, that embodiments of the present disclosure may be practiced without these specific

details. Several features described hereafter may each be used independently of one another or with any combination of other features. An individual feature may not address any of the problems discussed above or might address only some of the problems discussed above. 5
[0031] The ensuing description provides exemplary embodiments only, and is not
intended to limit the scope, applicability, or configuration of the disclosure. Rather,
the ensuing description of the exemplary embodiments will provide those skilled in
the art with an enabling description for implementing an exemplary embodiment.
10 It should be understood that various changes may be made in the function and
arrangement of elements without departing from the spirit and scope of the disclosure as set forth.
[0032] Specific details are given in the following description to provide a thorough
15 understanding of the embodiments. However, it will be understood by one of
ordinary skill in the art that the embodiments may be practiced without these specific details. For example, circuits, systems, processes, and other components may be shown as components in block diagram form in order not to obscure the embodiments in unnecessary detail. 20
[0033] Also, it is noted that individual embodiments may be described as a process
which is depicted as a flowchart, a flow diagram, a data flow diagram, a structure
diagram, or a block diagram. Although a flowchart may describe the operations as
a sequential process, many of the operations may be performed in parallel or
25 concurrently. In addition, the order of the operations may be re-arranged. A process
is terminated when its operations are completed but could have additional steps not included in a figure.
[0034] The word “exemplary” and/or “demonstrative” is used herein to mean
30 serving as an example, instance, or illustration. For the avoidance of doubt, the
subject matter disclosed herein is not limited by such examples. In addition, any
9

aspect or design described herein as “exemplary” and/or “demonstrative” is not
necessarily to be construed as preferred or advantageous over other aspects or
designs, nor is it meant to preclude equivalent exemplary structures and techniques
known to those of ordinary skill in the art. Furthermore, to the extent that the terms
5 “includes,” “has,” “contains,” and other similar words are used in either the detailed
description or the claims, such terms are intended to be inclusive—in a manner similar to the term “comprising” as an open transition word—without precluding any additional or other elements.
10 [0035] As used herein, a “processing unit” or “processor” or “operating processor”
includes one or more processors, wherein processor refers to any logic circuitry for processing instructions. A processor may be a general-purpose processor, a special purpose processor, a conventional processor, a digital signal processor, a plurality of microprocessors, one or more microprocessors in association with a (Digital
15 Signal Processing) DSP core, a controller, a microcontroller, Application Specific
Integrated Circuits, Field Programmable Gate Array circuits, any other type of integrated circuits, etc. The processor may perform signal coding data processing, input/output processing, and/or any other functionality that enables the working of the system according to the present disclosure. More specifically, the processor or
20 processing unit is a hardware processor.
[0036] As used herein, “a user equipment”, “a user device”, “a smart-user-device”, “a smart-device”, “an electronic device”, “a mobile device”, “a handheld device”, “a wireless communication device”, “a mobile communication device”, “a
25 communication device” may be any electrical, electronic and/or computing device
or equipment, capable of implementing the features of the present disclosure. The user equipment/device may include, but is not limited to, a mobile phone, smart phone, laptop, a general-purpose computer, desktop, personal digital assistant, tablet computer, wearable device or any other computing device which is capable
30 of implementing the features of the present disclosure. Also, the user device may
contain at least one input means configured to receive an input from at least one of
10

a transceiver unit, a processing unit, a storage unit, a detection unit and any other such unit(s) which are required to implement the features of the present disclosure.
[0037] As used herein, “storage unit” or “memory unit” refers to a machine or
5 computer-readable medium including any mechanism for storing information in a
form readable by a computer or similar machine. For example, a computer-readable
medium includes read-only memory (“ROM”), random access memory (“RAM”),
magnetic disk storage media, optical storage media, flash memory devices or other
types of machine-accessible storage media. The storage unit stores at least the data
10 that may be required by one or more units of the system to perform their respective
functions.
[0038] As used herein “interface” or “user interface refers to a shared boundary
across which two or more separate components of a system exchange information
15 or data. The interface may also be referred to a set of rules or protocols that define
communication or interaction of one or more modules or one or more units with each other, which also includes the methods, functions, or procedures that may be called.
20 [0039] The Serving Call Session Control Function (S-CSCF) is a component within
the IP Multimedia Subsystem (IMS) architecture. It's responsible for managing session control functions within the network, including call routing, session establishment, and service invocation. The Interrogating Call Session Control Function (I-CSCF) serves as the entry point for signalling messages entering the
25 IMS network. It interrogates these messages and routes them to the appropriate S-
CSCF based on predefined rules and policies.
[0040] User Authentication Request (UAR) is a message sent from the network to
the Home Subscriber Server (HSS) to verify the identity of a user attempting to
30 access services. The HSS, a database within the telecommunications network,
stores subscriber information, including authentication and authorization data.
11

Upon receiving the UAR, the HSS processes the request and generates a User Authorization Answer (UAA), containing authorization information for the requested service.
5 [0041] Disaster or service disruption at the primary site, the system may need to
migrate traffic to a backup location known as the Disaster Recovery (DR) site. This process requires seamless transition mechanisms to ensure continuity of service.
[0042] Forceful selection refers to a mode or setting within the system that
10 mandates the selection of a specific option or action, often necessary during
scenarios like disaster recovery. The forceful selection mode being ON is a
predetermined configuration within the system that compels the I-CSCF unit to
prioritize the selection of the PR site S-CSCF. . This mode is particularly significant
during disaster recovery operations, ensuring that call sessions and subscriber data
15 are redirected to the primary recovery site irrespective of the standard selection
criteria.
[0043] The 480 signal is a response code indicating that the callee's end system is temporarily unavailable. It serves as a means to inform the caller that the requested
20 action cannot be completed at the moment, typically triggering subsequent actions
or protocols to manage the situation, such as S-CSCF restoration processes. The "480 signal" refers to the SIP (Session Initiation Protocol) response code "480 Temporarily Unavailable." In the context of the described method, it signifies that the DR (Disaster Recovery) S-CSCF (Serving Call Session Control Function) is
25 temporarily unavailable to handle the request.
[0044] All modules, units, components used herein, unless explicitly excluded
herein, may be software modules or hardware processors, the processors being a
general-purpose processor, a special purpose processor, a conventional processor,
30 a digital signal processor (DSP), a plurality of microprocessors, one or more
microprocessors in association with a DSP core, a controller, a microcontroller,
12

Application Specific Integrated Circuits (ASIC), Field Programmable Gate Array circuits (FPGA), any other type of integrated circuits, etc.
[0045] As used herein the transceiver unit include at least one receiver and at least
5 one transmitter configured respectively for receiving and transmitting data, signals,
information or a combination thereof between units/components within the system and/or connected with the system.
[0046] As discussed in the background section, for existing solutions, the migration
10 process from DR to PR can be complex and time-consuming. It requires careful
planning, coordination, and testing to ensure a smooth transition. The configuration changes, protocol adaptations, and interoperability testing involved can increase the complexity of the migration. Further, the migration process requires network resources as devices will be forcefully de-registered. This can result in increased
15 resource utilization. Also, during the migration process, there is a possibility of
service disruptions or downtime. It is crucial to carefully plan and execute the migration to minimize any negative impact on ongoing services and end-user experience. While migrating from DR to PR in the S-CSCF can offer benefits like improved scalability, simplified network architecture, and reduced signaling load,
20 it is crucial to carefully assess and mitigate the potential disadvantages to ensure a
successful migration. Further, over the period of time various solutions have been developed to improve the performance of communication devices and for seamless traffic migration from DR to PR in SIB node. However, there are certain challenges with existing solutions.
25
[0047] To overcome these and other inherent problems in the art, the present disclosure proposes a solution of seamless traffic migration from a disaster recovery (DR) site to a primary recovery (PR) site, which significantly streamlines the transition process without the need for graceful deregistration of users. This
30 approach reduces network usage and avoids the complexities associated with the
traditional migration process. By employing an Interrogating Call Session Control
13

Function (I-CSCF) that can forcefully select a PR site Serving Call Session Control
Function (S-CSCF) regardless of the current server status, the invention ensures a
continuous and seamless service experience for users. Furthermore, the method
involves a special protocol where the I-CSCF sends a REGISTER request with a
5 unique identifier (magic cookie) to the DR S-CSCF, prompting it to clear its
bindings with subscribers immediately, which mitigates the risk of data conflicts or duplication during the migration process. The introduction of a System Integration Bus (SIB) node supports two distinct options for S-CSCF re-selection, 'ALWAYS' and 'S-CSCF-INITIATED', which provide flexibility in handling different
10 migration scenarios and ensuring higher availability and reliability of the network.
The 'ALWAYS' option allows the I-CSCF to proactively query the Home Subscriber Server (HSS) and make a forceful selection of the PR S-CSCF, which is prioritized over the DR S-CSCF even if the latter is still operational. This proactive capability ensures that the network can quickly adapt to changes and recover from
15 any disaster scenarios with minimal disruption to the user.
[0048] It would be appreciated by the person skilled in the art that the present
disclosure effectively addresses the challenges of increased network load, complex
migration protocols, and potential service disruptions that are prevalent in the prior
20 art by introducing a more efficient, flexible, and user-transparent method of S-
CSCF migration in telecommunications networks.
[0049] Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the accompanying drawings.
25
[0050] FIG. 1 illustrates an exemplary block diagram representation of 5th generation core (5GC) network architecture, in accordance with exemplary implementation of the present disclosure. As shown in FIG. 1, the 5GC network architecture [100] includes a user equipment (UE) [102], a radio access network
30 (RAN) [104], an access and mobility management function (AMF) [106], a Session
Management Function (SMF) [108], a Service Communication Proxy (SCP) [110],
14

an Authentication Server Function (AUSF) [112], a Network Slice Specific
Authentication and Authorization Function (NSSAAF) [114], a Network Slice
Selection Function (NSSF) [116], a Network Exposure Function (NEF) [118], a
Network Repository Function (NRF) [120], a Policy Control Function (PCF) [122],
5 a Unified Data Management (UDM) [124], an application function (AF) [126], a
User Plane Function (UPF) [128], a data network (DN) [130], wherein all the components are assumed to be connected to each other in a manner as obvious to the person skilled in the art for implementing features of the present disclosure.
10 [0051] Radio Access Network (RAN) [104] is the part of a mobile
telecommunications system that connects user equipment (UE) [102] to the core network (CN) and provides access to different types of networks (e.g., 5G network). It consists of radio base stations and the radio access technologies that enable wireless communication.
15
[0052] Access and Mobility Management Function (AMF) [106] is a 5G core network function responsible for managing access and mobility aspects, such as UE registration, connection, and reachability. It also handles mobility management procedures like handovers and paging.
20
[0053] Session Management Function (SMF) [108] is a 5G core network function responsible for managing session-related aspects, such as establishing, modifying, and releasing sessions. It coordinates with the User Plane Function (UPF) for data forwarding and handles IP address allocation and QoS enforcement.
25
[0054] Service Communication Proxy (SCP) [110] is a network function in the 5G core network that facilitates communication between other network functions by providing a secure and efficient messaging service. It acts as a mediator for service-based interfaces.
30
15

[0055] Authentication Server Function (AUSF) [112] is a network function in the 5G core responsible for authenticating UEs during registration and providing security services. It generates and verifies authentication vectors and tokens.
5 [0056] Network Slice Specific Authentication and Authorization Function
(NSSAAF) [114] is a network function that provides authentication and authorization services specific to network slices. It ensures that UEs can access only the slices for which they are authorized.
10 [0057] Network Slice Selection Function (NSSF) [116] is a network function
responsible for selecting the appropriate network slice for a UE based on factors such as subscription, requested services, and network policies.
[0058] Network Exposure Function (NEF) [118] is a network function that exposes
15 capabilities and services of the 5G network to external applications, enabling
integration with third-party services and applications.
[0059] Network Repository Function (NRF) [120] is a network function that acts
as a central repository for information about available network functions and
20 services. It facilitates the discovery and dynamic registration of network functions.
[0060] Policy Control Function (PCF) [122] is a network function responsible for policy control decisions, such as QoS, charging, and access control, based on subscriber information and network policies. 25
[0061] Unified Data Management (UDM) [124] is a network function that centralizes the management of subscriber data, including authentication, authorization, and subscription information.
16

[0062] Application Function (AF) [126] is a network function that represents external applications interfacing with the 5G core network to access network capabilities and services.
5 [0063] User Plane Function (UPF) [128] is a network function responsible for
handling user data traffic, including packet routing, forwarding, and QoS enforcement.
[0064] Data Network (DN) [130] refers to a network that provides data services to
10 user equipment (UE) in a telecommunications system. The data services may
include but are not limited to Internet services, private data network related services.
[0065] FIG. 2 illustrates an exemplary block diagram of a computing device [200] upon which an embodiment of the present disclosure may be implemented. In an
15 implementation, the computing device implements the method for traffic migration
from a disaster recovery (DR) site to a primary recovery (PR) site in a Serving Call Session Control Function (S-CSCF) in a 4G/5G network using the system. In another implementation, the computing device itself implements the method for traffic migration from a disaster recovery (DR) site to a primary recovery (PR) site
20 in a Serving Call Session Control Function (S-CSCF) in a 4G/5G network by using
one or more units configured within the computing device, wherein said one or more units are capable of implementing the features as disclosed in the present disclosure.
25 [0066] The computing device [200] may include a bus [202] or other
communication mechanism for communicating information, and a hardware processor [204] coupled with bus [202] for processing information. The hardware processor [204] may be, for example, a general purpose microprocessor. The computing device [200] may also include a main memory [206], such as a random
30 access memory (RAM), or other dynamic storage device, coupled to the bus [202]
for storing information and instructions to be executed by the processor [204]. The
17

main memory [206] also may be used for storing temporary variables or other
intermediate information during execution of the instructions to be executed by the
processor [204]. Such instructions, when stored in non-transitory storage media
accessible to the processor [204], render the computing device [200] into a special-
5 purpose machine that is customized to perform the operations specified in the
instructions. The computing device [200] further includes a read only memory
(ROM) [208] or other static storage device coupled to the bus [202] for storing static
information and instructions for the processor [204].
10 [0067] A storage device [210], such as a magnetic disk, optical disk, or solid-state
drive is provided and coupled to the bus [202] for storing information and instructions. The computing device [200] may be coupled via the bus [202] to a display [212], such as a cathode ray tube (CRT), Liquid crystal Display (LCD), Light Emitting Diode (LED) display, Organic LED (OLED) display, etc. for
15 displaying information to a computer user. An input device [214], including
alphanumeric and other keys, touch screen input means, etc. may be coupled to the bus [202] for communicating information and command selections to the processor [204]. Another type of user input device may be a cursor controller [216], such as a mouse, a trackball, or cursor direction keys, for communicating direction
20 information and command selections to the processor [204], and for controlling
cursor movement on the display [212]. This input device typically has two degrees of freedom in two axes, a first axis (e.g., x) and a second axis (e.g., y), that allow the device to specify positions in a plane.
25 [0068] The computing device [200] may implement the techniques described
herein using customized hard-wired logic, one or more ASICs or FPGAs, firmware and/or program logic which in combination with the computing device [200] causes or programs the computing device [200] to be a special-purpose machine. According to one implementation, the techniques herein are performed by the
30 computing device [200] in response to the processor [204] executing one or more
sequences of one or more instructions contained in the main memory [206]. Such
18

instructions may be read into the main memory [206] from another storage medium,
such as the storage device [210]. Execution of the sequences of instructions
contained in the main memory [206] causes the processor [204] to perform the
process steps described herein. In alternative implementations of the present
5 disclosure, hard-wired circuitry may be used in place of or in combination with
software instructions.
[0069] The computing device [200] also may include a communication interface
[218] coupled to the bus [202]. The communication interface [218] provides a two-
10 way data communication coupling to a network link [220] that is connected to a
local network [222]. For example, the communication interface [218] may be an
integrated services digital network (ISDN) card, cable modem, satellite modem, or
a modem to provide a data communication connection to a corresponding type of
telephone line. As another example, the communication interface [218] may be a
15 local area network (LAN) card to provide a data communication connection to a
compatible LAN. Wireless links may also be implemented. In any such
implementation, the communication interface [218] sends and receives electrical,
electromagnetic or optical signals that carry digital data streams representing
various types of information.
20
[0070] The computing device [200] can send messages and receive data, including
program code, through the network(s), the network link [220] and the
communication interface [218]. In the Internet example, a server [230] might
transmit a requested code for an application program through the Internet [228], the
25 ISP [226], the host [224], the local network [222] and the communication interface
[218]. The received code may be executed by the processor [204] as it is received, and/or stored in the storage device [210], or other non-volatile storage for later execution.
30 [0071] Referring to FIG. 3, an exemplary block diagram of a system [300] for
traffic migration from a disaster recovery (DR) site to a primary recovery (PR) site
19

in a Serving Call Session Control Function (S-CSCF) in a 4G/5G network, is
shown, in accordance with the exemplary implementations of the present
disclosure. The system [300] comprises at least one transceiver unit [302], at least
one fetching unit [304], at least one verification unit [306], at least one initiating
5 unit [308], at least one clarification unit [310], at least one an interrogating call
session control function (I-CSCF) unit [312], at least one Disaster Recovery Serving Call Session Control Function (DR S-CSCF) unit [314], user authentication request (UAR) [316], user authorization answer (UAA) [318], system integration bus (SIB) node [320], and home subscriber server (HSS) [324]. Also, all of the
10 components/ units of the system [300] are assumed to be connected to each other
unless otherwise indicated below. As shown in the figures all units shown within the system should also be assumed to be connected to each other. Also, in FIG. 3 only a few units are shown, however, the system [300] may comprise multiple such units or the system [300] may comprise any such numbers of said units, as required
15 to implement the features of the present disclosure. Further, in an implementation,
the system [300] may be present in a user device to implement the features of the present disclosure. In another implementation, the system [300] may reside in a server or a network entity. In yet another implementation, the system [300] may reside partly in the server/ network entity and partly in the user device.
20
[0072] The system [300] is configured for traffic migration from a disaster recovery (DR) site to a primary recovery (PR) site in a Serving Call Session Control Function (S-CSCF) in a 4G/5G network with the help of the interconnection between the components/units of the system [300].
25
[0073] The system for traffic migration from a disaster recovery (DR) site to a primary recovery (PR) site in a Serving Call Session Control Function (S-CSCF) in a 4G/5G network, the system comprising a transceiver unit [302] configured to receive, at an interrogating call session control function (I-CSCF) unit [312], a
30 signal to initiate migration. When the system detects a need to migrate traffic, it
sends a signal to the Interrogating Call Session Control Function (I-CSCF) unit.
20

The I-CSCF unit is responsible for handling initial signalling messages within the
network. Upon receiving the migration signal, it initiates the process by triggering
the necessary actions within the system to facilitate transfer of traffic from the DR
site to the PR site. The signal acts as the trigger for the entire migration protocol,
5 indicating that conditions at the DR site necessitate a switch to the PR site to
maintain service continuity and network performance.
[0074] The transceiver unit [302] is further configured to send from the I_CSCF unit [312], a user authentication request (UAR) to a home subscriber server (HSS)
10 [324] to obtain a server name, wherein the server name is Disaster Recovery
Serving Call Session Control Function (DR S-CSCF) UNIT [314].The present disclosure encompasses the Interrogating Call Session Control Function (I-CSCF) unit [312] sending a User Authentication Request (UAR) to the Home Subscriber Server (HSS) [324]. The purpose of this request is to authenticate the user and
15 obtain a server name. The system verifies the identity of the user and retrieves
necessary information from the HSS [324], such as the server’s name wherein the server name is Disaster Recovery Serving Call Session Control Function (DR S-CSCF) UNIT [314]. The UAR [316] is an signaling message used within the IMS architecture that requests information about the current location and service settings
20 of a subscriber. By sending the UAR [316], the I-CSCF unit [312] seeks to retrieve
the server name of the Serving Call Session Control Function (S-CSCF) that is currently managing the user's session.
[0075] The system [300] may further include a fetching unit [304] connected to at
25 least the transceiver unit [302], wherein the fetching unit [304] is configured to
obtain, at the I-CSCF unit [312], the server name from the HSS [324] through a
User Authorization Answer (UAA) [318]. After the transceiver unit [302] sends the
User Authentication Request (UAR) [316] to the Home Subscriber Server (HSS)
[324] and receives a response, the fetching unit [304] retrieves essential details
30 contained in the UAA [318]. The UAA [318], which is a response from the HSS
[324], provides the server name of the Serving Call Session Control Function (S-
21

CSCF) that currently handles the user's session. This information is vital for the I-
CSCF to correctly route calls and sessions, particularly during scenarios requiring
the migration of services from a disaster recovery (DR) site to a primary recovery
(PR) site. By ensuring that the fetching unit can accurately and efficiently extract
5 this information, the network can maintain seamless service continuity and
effectively manage user sessions across its infrastructure.
[0076] The system [300] may further include a verification unit [306] connected to at least the fetching unit [304], wherein the verification unit [306] is configured to
10 verify at the I-CSCF unit [312], whether a forceful selection mode is ON, and if the
obtained server name corresponds to a DR site. Once the fetching unit [304] retrieves the server name from the Home Subscriber Server (HSS) [324] through the User Authorization Answer (UAA) [318], the verification unit [306] assesses whether the current network conditions or policies require a forceful migration from
15 the DR site to the PR site. This is determined by checking if the forceful selection
mode is activated, which is a setting that could be triggered by various conditions such as server overload, maintenance requirements, or disaster recovery protocols. Additionally, the verification unit [306] checks if the retrieved server name is associated with a DR site, for initiating protocols designed to switch operations to
20 a PR site seamlessly.
[0077] The initiating unit [308] is communicatively coupled to the verification unit [306]. The initiating unit [308] is configured to initiate, from the I-CSCF unit [312], a protocol for traffic migration based on determining that the obtained server name
25 is of the DR site and forceful selection is in an ON state. Upon confirmation, the
initiating unit [308] utilizes a protocol for traffic migration from the DR site to the PR site is executed without disruption to ongoing services. The protocol, thus, facilitates in maintaining service continuity and quality, particularly in scenarios that demand high availability and resilience, such as in disaster recovery situations.
30 Through these actions, the initiating unit [308] ensures that network operations can
22

be smoothly transitioned to the PR site, thus safeguarding user experience and network performance.
[0078] The transceiver unit [302] is further configured to send, at the I-CSCF, the
5 UAR with capabilities option to the HSS [324] to facilitate selection of the PR site
S-CSCF. The transceiver unit [302] thus facilitates in streamlining the transition process from a disaster recovery (DR) site to a primary recovery (PR) site. The capabilities option within the UAR facilitates in notifying the HSS [324] of the functional and service requirements necessary for the PR site S-CSCF, such as
10 support for high-definition voice, video calling capabilities, or enhanced security
features. Including these specifications enables the HSS [324] to select an S-CSCF at the PR site that best matches the outlined requirements, ensuring that the network can maintain optimal service levels during and after the transition. The traffic migration is supported by a System Integration Bus (SIB) node [320]. The SIB node
15 [320] supports two options for S-CSCF re-selection, comprising ALWAYS option
and S-CSCF-INITIATED option. In the ALWAYS option, the I-CSCF unit [312] queries the HSS [324 through the UAR [316] and receive UAA [318] to obtain the server name corresponding to the DR S-CSCF unit [314], and in response to the forceful selection being ON and the server name being from the DR site, sends the
20 UAR [316] with the capabilities option. The capabilities option includes
specifications such as support for high-definition voice service, video call functionality, and enhanced data security features. The specifications are used to determine whether the Serving Call Session Control Function (S-CSCF) supports essential services such as emergency calls, session timers, or various media types.
25 The capabilities option ensures that the selected S-CSCF can handle specific user
needs and service requirements effectively, thereby enhancing the overall quality of service and security provided to users.
[0079] The DR S-CSCF unit [314] is configured to receive, via the transceiver unit
30 [302], a register request from the I-CSCF unit [312]. When the DR S-CSCF unit
receives a register request from the I-CSCF unit via the transceiver unit, it proceeds
23

to process the request. When the I-CSCF unit sends a REGISTER request to the DR
S-CSCF unit, it triggers the clearing of subscriber data by the DR S-CSCF. This
action is necessary to prevent data conflicts and ensure an accurate update of session
information. Furthermore, the DR S-CSCF's response with a 480 signal to the I-
5 CSCF initiates the S-CSCF restoration process, prompting the redirection of traffic
to the PR site. This involves clear, via a clarification unit [310], subscriber data in
response to the register request, which means removing or resetting any existing
subscriber-related information stored within the DR S-CSCF unit [314]. The DR S-
CSCF unit [314] facilitates in handling new registrations and requests without any
10 residual data from previous sessions. Once the subscriber data has been cleared, the
DR S-CSCF unit [314] responds, the transceiver unit [302], with a 480 signal to the I-CSCF unit [312] wherein the I-CSCF unit [312], upon receiving the 480 signal, triggers an S-CSCF restoration. The DR S-CSCF unit effectively handles register requests, clears any existing subscriber data, and communicates its availability
15 status to the I-CSCF unit within the network infrastructure.
[0080] Referring to FIG. 4, an exemplary method flow diagram [400] for traffic migration from a disaster recovery (DR) site to a primary recovery (PR) site in a Serving Call Session Control Function (S-CSCF) in a 4G/5G network, in
20 accordance with exemplary implementations of the present disclosure is shown. In
an implementation the method [400] is performed by the system [300]. Further, in an implementation, the system [300] may be present in a server device to implement the features of the present disclosure. Also, as shown in FIG. 4, the method [400] starts at step [402].
25
[0081] At step 404, the method comprises, receiving, by a transceiver unit [302], at an interrogating call session control function (I-CSCF) unit [312], a signal to initiate migration. When the system detects a need to migrate traffic, it sends a signal to the Interrogating Call Session Control Function (I-CSCF) unit. The I-CSCF unit is
30 responsible for handling initial signalling messages within the network. Upon
receiving the migration signal, it initiates the process by triggering the necessary
24

actions within the system to facilitate transfer of traffic from the DR site to the PR site. The signal acts as the trigger for the entire migration protocol, indicating that conditions at the DR site necessitate a switch to the PR site to maintain service continuity and network performance. 5
[0082] At step 406, the method comprises, sending, by the transceiver unit [302],
from the I-CSCF unit [312], a user authentication request (UAR) [316] to a home
subscriber server (HSS) [324] to obtain a server name wherein the server name is
Disaster Recovery Serving Call Session Control Function (DR S-CSCF) unit [314].
10 The present disclosure encompasses the Interrogating Call Session Control
Function (I-CSCF) unit [312] sending a User Authentication Request (UAR) to the
Home Subscriber Server (HSS) [324]. The purpose of this request is to authenticate
the user and obtain a server name. The system verifies the identity of the user and
retrieves necessary information from the HSS [324], such as the server’s name
15 wherein the server name is Disaster Recovery Serving Call Session Control
Function (DR S-CSCF) UNIT [314]. The UAR [316] is an signaling message used
within the IMS architecture that requests information about the current location and
service settings of a subscriber. By sending the UAR [316], the I-CSCF unit [312]
seeks to retrieve the server name of the Serving Call Session Control Function (S-
20 CSCF) that is currently managing the user's session.
[0083] At step 408, the method comprises, obtaining, by a fetching unit [304], at the I-CSCF unit [312], the server name from the HSS [324] through a User Authorization Answer (UAA) [318]. After the transceiver unit [302] sends the User
25 Authentication Request (UAR) [316] to the Home Subscriber Server (HSS) [324]
and receives a response, the fetching unit [304] retrieves essential details contained in the UAA [318]. The UAA [318], which is a response from the HSS [324], provides the server name of the Serving Call Session Control Function (S-CSCF) that currently handles the user's session. This information is vital for the I-CSCF to
30 correctly route calls and sessions, particularly during scenarios requiring the
migration of services from a disaster recovery (DR) site to a primary recovery (PR)
25

site. By ensuring that the fetching unit can accurately and efficiently extract this information, the network can maintain seamless service continuity and effectively manage user sessions across its infrastructure.
5 [0084] At step 410, the method comprises, verifying, by a verification unit [306],
at the I-CSCF unit [312], whether a forceful selection mode is ON, and if the obtained server name corresponds to a DR site. Once the fetching unit [304] retrieves the server name from the Home Subscriber Server (HSS) [324] through the User Authorization Answer (UAA) [318], the verification unit [306] assesses
10 whether the current network conditions or policies require a forceful migration from
the DR site to the PR site. This is determined by checking if the forceful selection mode is activated, which is a setting that could be triggered by various conditions such as server overload, maintenance requirements, or disaster recovery protocols. Additionally, the verification unit [306] checks if the retrieved server name is
15 associated with a DR site, for initiating protocols designed to switch operations to
a PR site seamlessly.
[0085] At step 412, the method comprises based on determining that the obtained server name is of the DR site and forceful selection is in an ON state, initiating, by
20 an initiating unit [308], from the I-CSCF unit [312], a protocol for traffic migration
to the PR site. Upon confirmation, the initiating unit [308] utilizes a protocol for traffic migration from the DR site to the PR site is executed without disruption to ongoing services. The protocol, thus, facilitates in maintaining service continuity and quality, particularly in scenarios that demand high availability and resilience,
25 such as in disaster recovery situations. Through these actions, the initiating unit
[308] ensures that network operations can be smoothly transitioned to the PR site, thus safeguarding user experience and network performance.
[0086] At step 414, the method comprises, sending, by the transceiver unit [302],
30 at the I-CSCF unit [312], the UAR with capabilities option to the HSS [324] to
facilitate selection of the PR site S-CSCF. The transceiver unit [302] thus facilitates
26

in streamlining the transition process from a disaster recovery (DR) site to a primary
recovery (PR) site. The capabilities option within the UAR facilitates in notifying
the HSS [324] of the functional and service requirements necessary for the PR site
S-CSCF, such as support for high-definition voice, video calling capabilities, or
5 enhanced security features. Including these specifications enables the HSS [324] to
select an S-CSCF at the PR site that best matches the outlined requirements, ensuring that the network can maintain optimal service levels during and after the transition. The traffic migration is supported by a System Integration Bus (SIB) node [320]. The SIB node [320] supports two options for S-CSCF re-selection,
10 comprising ALWAYS option and S-CSCF-INITIATED option. In the ALWAYS
option, the I-CSCF unit [312] queries the HSS [324 through the UAR [316] and receive UAA [318] to obtain the server name corresponding to the DR S-CSCF unit [314], and in response to the forceful selection being ON and the server name being from the DR site, sends the UAR [316] with the capabilities option. The capabilities
15 option includes specifications such as support for high-definition voice service,
video call functionality, and enhanced data security features. The specifications are used to determine whether the Serving Call Session Control Function (S-CSCF) supports essential services such as emergency calls, session timers, or various media types. The capabilities option ensures that the selected S-CSCF can handle
20 specific user needs and service requirements effectively, thereby enhancing the
overall quality of service and security provided to users.
[0087] Thereafter, the method terminates at step [416].
25 [0088] Further, the method comprises receiving, via the transceiver unit [302], by
the DR S-CSCF unit [314], a REGISTER request from the I-CSCF unit [312]. When the DR S-CSCF unit [314] receives a register request from the I-CSCF unit [312] via the transceiver unit, it proceeds to process the request. This involving clearing, via a clarification unit [310], by the DR S-CSCF unit [314], a subscriber
30 data in response to the REGISTER request which means removing or resetting any
existing subscriber-related information stored within the DR S-CSCF unit [314].
27

This step ensures that the DR S-CSCF unit [314] is ready to handle new
registrations and requests without any residual data from previous sessions. Once
the subscriber data has been cleared, the DR S-CSCF unit [314] responding, via the
transceiver unit [302], by the DR S-CSCF unit [314], with a 480 signal to the I-
5 CSCF unit [312] wherein the I-CSCF unit [312], upon receiving the 480 signal,
triggers an S-CSCF restoration. The DR S-CSCF unit [314] effectively handles
register requests, clears any existing subscriber data, and communicates its
availability status to the I-CSCF unit [312] within the network infrastructure.
10 [0089] FIG. 5A illustrates an exemplary sequence diagram [500] indicating SCSCF
Re-Selection-Always Option for traffic migration from a disaster recovery (DR) site to a primary recovery (PR) site in a Serving Call Session Control Function (S-CSCF) in a 4G/5G network, in accordance with exemplary implementations of the present disclosure.
15
[0090] The process starts with a user equipment (UE) [102] initiating a session in the network. This triggers the Proxy Call Session Control Function (P-CSCF) [502] to forward the request to the Interrogating Call Session Control Function (I-CSCF) [312]. The I-CSCF [312], upon receiving the request, checks if the forceful
20 selection mode is activated and the reselection method is set to 'Always'. With both
conditions met, the I-CSCF [312] proceeds to request the user's server name from the Home Subscriber Server (HSS) [324]. If the server name obtained corresponds to the Disaster Recovery (DR) S-CSCF [314], the I-CSCF [312] then sends a User Authentication Request (UAR) [316] with a capabilities option to the HSS [324].
25 The option is used to determine whether the Serving Call Session Control Function
(S-CSCF) can support specific services required by the user, such as high-definition voice or video call functionality. Based on the capabilities and priority level, the HSS [324] selects the Primary S-CSCF [504] to handle the session. The Primary S-CSCF [504] sends a 401 code. As would be understood, code ‘401’ may indicate
30 ‘UNAUTHORIZED’ status. Such unauthorized status and corresponding ‘401’
code occurs in the events of improper or invalied authentication credentials. In the
28

context of the present example, ‘401’ code may indicate an authentication challenge towards the UE [102]. This sequence ensures that traffic is seamlessly migrated to the primary site without unnecessary deregistration of users at the DR site, optimizing network usage and enhancing the user experience. 5
[0091] FIG. 5B illustrates an exemplary sequence diagram [500A] indicating
SCSCF Re-Selection-SCSCF-INITIATED Option for traffic migration from a
disaster recovery (DR) site to a primary recovery (PR) site in a Serving Call Session
Control Function (S-CSCF) in a 4G/5G network, in accordance with exemplary
10 implementations of the present disclosure.
[0092] The process starts with the I-CSCF [312] detecting that the forceful selection mode is ON, indicating a need for a potential re-selection of the Serving Call Session Control Function (S-CSCF) due to a fallback to the local super core.
15 Once the reselection method is confirmed as SCSCF-INITIATED, the I-CSCF
[312] initiates contact with the current DR S-CSCF [314] by sending a REGISTER request. Upon receiving this REGISTER request, the DR S-CSCF [314] proceeds to clear the subscriber's data, effectively deregistering the user from the DR site without requiring a graceful deregistration process. After successfully clearing the
20 data, the DR S-CSCF [314] sends a 480 response back to the I-CSCF [312]. This
480 signal indicates that the subscriber's information has been cleared, and the S-CSCF is ready for the next step. Subsequently, the I-CSCF [312], upon receiving the 480 signal, proceeds with the SCSCF restoration process. As part of this restoration, the I-CSCF [312] sends a query to the Home Subscriber Server (HSS)
25 [324], which now includes a request for capabilities, leveraging the UAR with the
capabilities option. The capabilities option aids the HSS [324] in selecting the appropriate Primary S-CSCF [504] based on the highest priority, ensuring that the services required by the user are supported by the newly selected S-CSCF. The Primary S-CSCF [504] sends a 401 code i.e. an authentication challenge towards
30 the UE [102]. This action concludes the SCSCF Re-Selection-SCSCF-INITIATED
Option, transitioning the user to the PR site in a way that is seamless and transparent
29

to the user, thereby maintaining the integrity of the user's experience and the efficiency of the network operation.
[0093] The present disclosure further discloses a non-transitory computer readable
5 storage medium storing instructions for traffic migration from a disaster recovery
(DR) site to a primary recovery (PR) site in a Serving Call Session Control Function (S-CSCF) in a 4G/5G network the instructions include executable code which, when executed by a one or more units of a system, causes: a transceiver unit of the system to receive, at an interrogating call session control function (I-CSCF) unit, a
10 signal to initiate migration; send from the I_CSCF unit, a user authentication
request (UAR) to a home subscriber server (HSS) to obtain a server name; a fetching unit of the system to obtain, at the I-CSCF unit, the server name from the HSS through a User Authorization Answer (UAA); a verification unit of the system to verify at the I-CSCF unit, whether a forceful selection mode is ON, and if the
15 obtained server name corresponds to a DR site; based on determining that the
obtained server name is of the DR site and forceful selection is in an ON state, an initial unit of the system to initiating, from the I-CSCF unit, a protocol for traffic migration the transceiver unit of the system to send, at the I-CSCF, the UAR with capabilities option to the HSS to facilitate selection of the PR site S-CSCF.
20
[0094] As is evident from the above, the present disclosure provides a
technically advanced solution for seamless traffic migration from DR to PR in SIB node. Further, the present solution enhances user experience even in unforeseen circumstances. Furthermore, provide a solution to ensure efficient use of network
25 resources.
[0095] While considerable emphasis has been placed herein on the
disclosed implementations, it will be appreciated that many implementations can
be made and that many changes can be made to the implementations without
30 departing from the principles of the present disclosure. These and other changes in
the implementations of the present disclosure will be apparent to those skilled in
30

the art, whereby it is to be understood that the foregoing descriptive matter to be implemented is illustrative and non-limiting.
[0096] Further, in accordance with the present disclosure, it is to be acknowledged
5 that the functionality described for the various the components/units can be
implemented interchangeably. While specific embodiments may disclose a
particular functionality of these units for clarity, it is recognized that various
configurations and combinations thereof are within the scope of the disclosure. The
functionality of specific units as disclosed in the disclosure should not be construed
10 as limiting the scope of the present disclosure. Consequently, alternative
arrangements and substitutions of units, provided they achieve the intended functionality described herein, are considered to be encompassed within the scope of the present disclosure.
31

We Claim:
1. A method [400] for traffic migration from a disaster recovery (DR) site to a
primary recovery (PR) site in a Serving Call Session Control Function (S-CSCF) in
a 4G/5G network, the method comprising:
receiving [404], by a transceiver unit [302], at an interrogating call session control function (I-CSCF) unit [312], a signal to initiate migration;
sending [406], by the transceiver unit [302], from the I-CSCF unit [312], a user authentication request (UAR) [316] to a home subscriber server (HSS) [324] to obtain a server name;
obtaining [408], by a fetching unit [304], at the I-CSCF unit [312], the server name from the HSS [324] through a User Authorization Answer (UAA) [318];
verifying [410], by a verification unit [306], at the I-CSCF unit [312], whether a forceful selection mode is ON, and if the obtained server name corresponds to a DR site;
based on determining that the obtained server name is of the DR site and forceful selection is in an ON state, initiating [412], by an initiating unit [308], from the I-CSCF unit [312], a protocol for traffic migration to the PR site; and
sending [414], by the transceiver unit [302], at the I-CSCF unit [312], the UAR [316] with capabilities option to the HSS [324] to facilitate selection of the PR site S-CSCF.
2. The method [400] as claimed in claim 1, wherein the traffic migration is supported by a System Integration Bus (SIB) node [320].
3. The method [400] as claimed in claim 1, wherein the server name is Disaster Recovery Serving Call Session Control Function (DR S-CSCF) unit [314].
4. The method [400] as claimed in claim 1, wherein the UAR [316] with capabilities option is sent to the HSS [324] to facilitate high priority-based selection of the PR site S-CSCF.

5. The method [400] as claimed in claim 3, further comprising:
receiving, via the transceiver unit [302], by the DR S-CSCF unit [314], a
REGISTER request from the I-CSCF unit [312];
clearing, via a clarification unit [310], by the DR S-CSCF unit [314], a subscriber data in response to the REGISTER request; and
responding, via the transceiver unit [302], by the DR S-CSCF unit [314], with a 480 signal to the I-CSCF unit [312].
6. The method [400] as claimed in claim 5, wherein the I-CSCF unit [312], upon receiving the 480 signal, triggers an S-CSCF restoration.
7. The method [400] as claimed in claim 2, wherein the SIB node [320] supports two options for S-CSCF re-selection, comprising ALWAYS option and S-CSCF-INITIATED option.
8. The method [400] as claimed in claim 7, wherein in the ALWAYS option, the I-CSCF unit [312] queries the HSS [324 through the UAR [316] and receive UAA [318] to obtain the server name corresponding to the DR S-CSCF unit [314], and in response to the forceful selection being ON and the server name being from the DR site, sends the UAR [316] with the capabilities option.
9. The method [400] as claimed in claim 1, wherein the capabilities option comprises at least one of a support for high-definition voice service, a video call functionality, and an enhanced data security feature for determining whether the S-CSCF supports at least one service from an emergency call, session timer, or a media type.
10. A system [300] for traffic migration from a disaster recovery (DR) site to a primary recovery (PR) site in a Serving Call Session Control Function (S-CSCF) in a 4G/5G network, the system comprising:

a transceiver unit [302] configured to:
receive, at an interrogating call session control function (I-CSCF)
unit [312], a signal to initiate migration; and
send from the I_CSCF unit [312], a user authentication request
(UAR) [316] to a home subscriber server (HSS) [324] to obtain a server
name;
a fetching unit [304] connected to at least the transceiver unit [302], wherein the fetching unit [304] is configured to obtain, at the I-CSCF unit [312],the server name from the HSS [324] through a User Authorization Answer (UAA) [318];
a verification unit [306] connected to at least the fetching unit [304], wherein the verification unit [306] is configured to verify at the I-CSCF unit [312], whether a forceful selection mode is ON, and if the obtained server name corresponds to a DR site;
based on determining that the obtained server name is of the DR site and forceful selection is in an ON state, an initiating unit [308] is connected to at least the verification unit [306], wherein the initiating unit [308] is configured to initiate, from the I-CSCF unit [312], a protocol for traffic migration; and
the transceiver unit [302] is configured to send, at the I-CSCF, the UAR [316] with capabilities option to the HSS [324] to facilitate selection of the PR site S-CSCF.
11. The system [300] as claimed in claim 10, wherein the traffic migration is supported by a System Integration Bus (SIB) node [320].
12. The system [300] as claimed in claim 10, wherein the server name is Disaster Recovery Serving Call Session Control Function (DR S-CSCF) unit [314].
13. The system [300] as claimed in claim 10, wherein the UAR [316] with capabilities option is sent to the HSS [324] to facilitate high priority-based selection of the PR site S-CSCF.

14. The system [300] as claimed in claim 12, wherein the DR S-CSCF unit [314]
is configured to:
receive, via the transceiver unit [302], a register request from the I-CSCF unit [312];
clear, via a clarification unit [310], a subscriber data in response to the register request; and
respond, the transceiver unit [302], with a 480 signal to the I-CSCF unit [312].
15. The system [300] as claimed in claim 14, wherein the I-CSCF unit [312], upon receiving the 480 signal, triggers an S-CSCF restoration.
16. The system [300] as claimed in claim 11, wherein the SIB node [320] supports two options for S-CSCF re-selection, comprising ALWAYS option and S-CSCF-INITIATED option.
17. The system [300] as claimed in claim 16, wherein in the ALWAYS option, the I-CSCF unit [312] queries the HSS [324] through the UAR [316] and receive UAA [318] to obtain the server name corresponding to the DR S-CSCF [314], and in response to the forceful selection being ON and the server name being from the DR site, sends the UAR [316] with the capabilities option.
18. The system [300] as claimed in claim 10, wherein the capabilities option comprises at least one of a support for high-definition voice service, a video call functionality, and an enhanced data security feature for determining whether the S-CSCF supports at least one service from an emergency call, session timer, or a media type.