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Questions and Answers
What is the primary function of an S-CSCF in IMS?
What is the primary function of an S-CSCF in IMS?
- To act as a mobile's first contact point inside a local IMS
- To generate Call Detail Records (CDRs) only
- To provide session control services for a user (correct)
- To act as a Policy Control Function (PCF)
What is one of the main tasks of an S-CSCF during registration?
What is one of the main tasks of an S-CSCF during registration?
- To generate Call Detail Records (CDRs) for accounting and billing
- To act as a SIP Proxy Server
- To make users' registration and location information available to location servers (correct)
- To control policy regarding how bearers in the packet-switched network should be used
What is the function of a P-CSCF in IMS?
What is the function of a P-CSCF in IMS?
- To act as a SIP Proxy Server (correct)
- To act as a Policy Control Function (PCF) only
- To provide session control services for a user
- To act as a Serving Call State Control Function
What is an S-CSCF responsible for during session control?
What is an S-CSCF responsible for during session control?
What is an additional function of an S-CSCF?
What is an additional function of an S-CSCF?
What does a P-CSCF include?
What does a P-CSCF include?
What does an S-CSCF act as during interactions with application servers?
What does an S-CSCF act as during interactions with application servers?
What is generated by an S-CSCF for accounting and billing?
What is generated by an S-CSCF for accounting and billing?
What is the main goal of IMS in the telecommunications industry?
What is the main goal of IMS in the telecommunications industry?
What kind of services can IMS provide?
What kind of services can IMS provide?
What is the main issue faced by fixed and mobile operators?
What is the main issue faced by fixed and mobile operators?
What is the focus of IMS architecture?
What is the focus of IMS architecture?
What is the advantage of IMS over proprietary solutions?
What is the advantage of IMS over proprietary solutions?
What is the goal of IMS in terms of service convergence?
What is the goal of IMS in terms of service convergence?
What kind of network does IMS support?
What kind of network does IMS support?
What is the benefit of IMS for subscribers?
What is the benefit of IMS for subscribers?
What is the primary focus of IMS standardization in 3GPP Release 5?
What is the primary focus of IMS standardization in 3GPP Release 5?
What is the main benefit of IMS from an end-user perspective?
What is the main benefit of IMS from an end-user perspective?
What is the role of SIP in IMS?
What is the role of SIP in IMS?
What is the main benefit of IMS from an operator perspective?
What is the main benefit of IMS from an operator perspective?
What is the main benefit of IMS from a general perspective?
What is the main benefit of IMS from a general perspective?
What is the primary focus of IMS standardization in 3GPP Release 6?
What is the primary focus of IMS standardization in 3GPP Release 6?
What is the main function of the Serving CSCF (S-CSCF)?
What is the main function of the Serving CSCF (S-CSCF)?
What is the scope of IMS extended in 3GPP Release 7?
What is the scope of IMS extended in 3GPP Release 7?
What type of information is stored in HSS?
What type of information is stored in HSS?
What is the primary function of the SLF?
What is the primary function of the SLF?
What protocol is used for communication between HSS and SLF?
What protocol is used for communication between HSS and SLF?
What is the function of the Media Gateway Control Function (MGCF)?
What is the function of the Media Gateway Control Function (MGCF)?
What information is used by the SLF to locate the correct HSS?
What information is used by the SLF to locate the correct HSS?
Is the SLF a mandatory component in IMS?
Is the SLF a mandatory component in IMS?
What is the function of the IM Media Gateway (IM-MGW)?
What is the function of the IM Media Gateway (IM-MGW)?
What is the primary function of the HSS?
What is the primary function of the HSS?
What is the primary function of the MRFP?
What is the primary function of the MRFP?
What is processed by the MRFP?
What is processed by the MRFP?
What is the role of the BGCF?
What is the role of the BGCF?
What is supported by the MRFP within the bearer path?
What is supported by the MRFP within the bearer path?
What is the role of the MRFC?
What is the role of the MRFC?
What is responsible for interfacing with internal and external service platforms?
What is responsible for interfacing with internal and external service platforms?
What is forwarded by the I-CSCF?
What is forwarded by the I-CSCF?
What type of platforms does the S-CSCF interface with?
What type of platforms does the S-CSCF interface with?
Study Notes
IMS (IP Multimedia Subsystem)
- IMS is a standardized solution in the telecommunications world that provides real-time multimedia sessions and non-real-time multimedia sessions over an all-IP network.
- IMS targets convergence of services supplied by different types of networks (fixed, mobile, Internet).
IMS Benefits
- Quality of Service enhancements
- New, exciting services and faster time to market with existing services
- Service integration and same services available regardless of terminal and access type
- Keeps charging relations with users and ease of use and security
- Controlling CAPEX and OPEX
IMS Standardization
- IMS was initially standardized by 3GPP (3rd Generation Partnership Projects) as part of its Release 5 specifications.
- 3GPP Release 6 targeted at supporting real-time services.
- 3GPP Release 7 standardization extended IMS scope to any IP access network, including fixed access networks (e.g., DSL).
IMS Architecture
- IMS provides all the network entities and procedures to support real-time voice and multimedia IP applications.
- IMS uses SIP to support signaling and session control for real-time services.
CSCF (Call State Control Function)
- Three types of CSCFs: Serving CSCF (S-CSCF), Proxy CSCF (P-CSCF), and Interrogating CSCF (I-CSCF).
- S-CSCF: provides session control services for a user, maintains session states, and performs registration, session control, proxy server, and interactions with application servers.
- P-CSCF: a mobile's first contact point inside a local IMS, acts as a SIP Proxy Server, and includes a Policy Control Function (PCF) to control policy regarding how bearers in the packet-switched network should be used.
Databases: HSS and SLF
- HSS (Home Subs Server): stores user data, authentication data, service profile, and charging information, and performs authentication and authorization of users.
- SLF (Subs Location Function): an optional component that helps locate the correct HSS in a large network, uses Diameter protocol to communicate with HSS.
IMS Entities
- MGCF (Media Gateway Control Function): responsible for signaling and media inter-working between PS domain and circuit-switched networks (e.g., PSTN).
- IM-MGW (IM Media Gateway): responsible for media inter-working between PS domain and circuit-switched networks.
- MRFP (Multimedia Resource Function Processor): provides resources to be controlled by the MRFC, sources media streams, processes media streams, and supports DTMF.
- MRFC (Multimedia Resource Function Controller): interprets signaling information from an S-CSCF or a SIP-based Application Server and controls the media streams resources in the MRFP.
- BGCF (Breakout Gateway Control Function): selects to which PSTN network a session should be forwarded.
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Description
Learn about the architecture of IMS, its core elements, interfaces, and application servers. Understand the basic call flow in IMS and its role in delivering various internet services.
