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IP Multimedia Subsystem Part 1 Marek Średniawa [email protected] Institute of Telecommunications Project is co-financed by European Union within the European Social Fund 1 EIMS - 2014

IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

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Page 1: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

IP Multimedia Subsystem

Part 1Marek Ś[email protected]

Institute of Telecommunications

Project is co-financed by European Union within the European Social Fund1EIMS - 2014

Page 2: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

Introduction

Page 3: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

3

Evolution of telecom

Service Delivery Platforms (SDPs)

INAP, CAP, CAMEL,

GSM

SIP, OSA/PARLAY,

JAIN, UMTS

IN

SCP & CSESwitching system

software

3G, NGN, IMS

Intelligence

embedded in

software of switching

systems

Intelligence

in a separate

service node

Intelligence

of cooperating

components

PSTN, ISDN

IP TV, RCS, APIs

(BONDI, REST, … )

4G, LTE, EPC,

SDP

Converged &

embedded

communications

EIMS - 2014

Page 4: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

4

Evolution of

service implementation model

Traditional closed model New open model

Physical

transport

Call control and

switching

Services and

applications

Physical transport

Multimedia session control

Services & applications +

management

API

API

Service interface

Network interface

Opening of the control infrastructure and service architecture using standard APIs - Parlay OSA/X APIs and JAIN APIs.

Breaking of the classic value chain. Separation of service development, deployment and operation. VNO and MVNO

models. EIMS - 2014

Page 5: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

5

Change of model: „Spaghetti”→„Lasagna”

„Spaghetti” type architecture „Lasagna” type architecture

Priv

ate

netw

orks

Fix

ed

netw

orks

Mo

bil

e n

etw

orks

Common service

capabilities

Transport and access

Application and content

EIMS - 2014

Page 6: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

6

Convergence - a buzzword …

• Overloaded concept – many flavours of „convergence”

• Voice - data

– Common transport network

• FMC

– ETSI TISPAN NGN

• Terminal convergence

– GSM/UMTS + WLAN

– Session continuity

– Single address (ENUM)

• Application convergence

– Context and presence embedded in applicatiions

– Click-to-call

EIMS - 2014

Page 7: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

7

Web 2.0/3.0

Mobility Wireless

access

Broadband

access

Convergence

Security

and

privacy

Open source

+

CopyLeft

Presence

and

context

Multimedia

Convergence – key factors

Computer science and Internet – Content, media, networked IT services

Telecommunications – A mix of solutions, technical and legal aspects

EIMS - 2014

Page 8: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

EIMS - 2014 8

Areas of convergence

Convergence planes

NetworkServices and

applicationsTerminals Charging Contents

Page 9: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

Everybody can offer (almost) everything …

EIMS - 2014

9

Internet

TV

Mobile

Fixed

Internet

TV

Mobile

Fixed

Internet

TV

Mobile

Fixed

Internet

TV

Mobile

Fixed

Market liberalization (LLU, BSA, ...) + business models (MVNO/MVNE, networked IT

services…) + resource sharing (fibers, lambdas, ducts, masts, servers, …)

Page 10: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

EIMS - 2014 10

IP Multimedia (IM) Domain• Implementation of multimedia services

• Integration of PS and CS domains and services

UMTS RNS

(UTRAN)

GSM

BSS

PDN

(IP)

PSTN

Core network

PS Domain

CS DomainME

Home

Domain

IM Domain - IMS

Page 11: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

EIMS - 2014 11

IMS integrates services

Voice

SMS

Instant

Messaging

MMS

Pre-IMS - „islands of services” IMS – integration of services

and combinational services

Voice / Video

SMS

Instant

Messaging

MMS

From separate usage of standalone services ... to integrated usage of services

based on presence

In groups – communities

PoC

TV

Page 12: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

EIMS - 2014 12

IMS - requirements

• Support for:– establishing IP Multimedia sessions

– mechanism to negotiate Quality of Service

– interworking with the Internet and circuit-switched networks

– Roaming

– strong control imposed by the operator with respect to the services delivered to the end-user

– rapid service creation without requiring standardization (service capability standardization)

– access from networks other than GPRS

Page 13: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

3GPP IP Multimedia Subsystem (1/2)

• IMS standardized by 3GPP as part of UMTS Release 5

– Basic VoIP, IM, Presence support on top of GPRS

– Adaptations to “real word” made in Release 6 (QoS, PoC support)

– Release 7 will look at unified IMS for all IP access networks (DSL, WLAN, etc.)

– Release 8 – Common IMS

• The IMS is based on the IP family of protocols:

– Adapted SIP (Session Initiation Protocol) for Session Control

– Diameter for AAA (Authentication, Authorization & Accounting)

– Others: SDP, RTP, RTCP, MGCP, etc.

EIMS - 2014 13

Page 14: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

3GPP IP Multimedia Subsystem (2/2)

• Key components of the IMS architecture:

– Extended AAA Server - Home Subscriber System – as

evolution of the HLR)

– SIP servers / softswitches

– Media Servers & Media Gateways

– Application Servers

EIMS - 2014 14

Page 15: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

EIMS - 2014

15

Standardization of NGN/3G and IMS

2001 2002 2003 2004

ITU-T NGN FG

2005

OASIS, OMA

3GPP Release 4

3GPP Release 5

3GPP Release 6

TISPAN NGN R1

3GPP2 MMD

3GPP Release 7

2006 2007

3GPP Release 8

2009

Common IMS

2011

3GPP Release 9

3GPP Release 10

2010

Page 16: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

3GPP Specifications

EIMS - 2014 16

Page 17: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

Evolution of UMTS

• LTE (Long Term Evolution) - 4G wireless access technology from 3GPP

• IP based only access and high bandwidth requirements implied 3GPP study of a

converged architecture to support it - System Architecture Evolution (SAE)

• The Evolved Packet Core (EPC) is the result of this study.

– All-IP architecture to which LTE and other 3GPP (UMTS,GPRS) and non-3GPP (WiMAX,HRPD,WLAN

etc) access systems connect to.

– EPC provides a converged solution for Security, QoS , Mobility and connection to the IP based

services (IMS or the Internet)

• Evolved Packet System (EPS) = EPC + LTE access network (E-UTRAN)

• IMS is on top of the EPC as one of the possible IP Services layer.

• Data interface (SGi) from the main gateway of the EPC (PDN-Gw) to IMS

• Signaling/control interface (Rx) from the application function (the P-CSCF in IMS)

to the main session controller in charge of the authorization, admission control,

resource reservation, QoS (PCRF)

EIMS - 2014 17

Page 18: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

EIMS - 201418

General IMS architecture

Source: 3GPP TS 23.002

Page 19: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

EIMS - 2014 19

Main 3GPP IMS standards

• 22.228: IP multimedia subsystem; Stage 1

• 23.207: End-to-end QoS Concepts and Architecture

• 23.218: IP Multimedia (IM) session handling; IM call model

• 23.228: IP Multimedia Subsystem (IMS); Stage 2

• 24.228: Signalling flows for the IP multimedia call control based on SIP and SDP; Stage 3

• 24.229: IP Multimedia Call Control Protocol based on SIP and SDP; Stage 3

• 29.228: IP Multimedia (IM) Subsystem Cx Interface; Signalling flows and message contents

• 29.229: Cx Interface based on the Diameter protocol; Protocol details

• 29.328: IP Multimedia Subsystem (IMS) Sh Interface; Signalling flows and message contents

• 29.329: Sh interface based on the Diameter protocol; Protocol details

• 29.207: Policy Control over Go Interface

• 29.208: End-to-end Quality of Service (QoS) signalling flows

• 32.200: Telecommunications management; Charging management; Charging principles

• 32.225: Telecommunications management; Charging management; Charging data description for the IMS domain

• 33.203: 3G security; Access security for IP-based services

• 33.210: 3G security; Network Domain Security (NDS); IP network layer security

Page 20: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

EIMS - 2014 20

From IETF SIP ….

Request

SIP Proxy server

IP/Internet

Response

DNSAS – SIP application server

SIP User Agent- UA

SIP User Agent- UASIP User Agent- UA

SIP User Agent- UA

Page 21: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

EIMS - 2014 21

… to 3GPP IMS SIP

P-CSCF

I-CSCFS-CSCF

Application server

DNS

SLF

DNS HSS

IP Core Network with QoS

support

AS – SIP application serwer

SIP User Agent- UA

SIP User Agent- UA

Page 22: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

EIMS - 2014

22

IMS in UMTS

CS Domain

PS Domain

“call”

“session”

IP core network

TDM, ATM or IP

MSC GMSC

SCP

IMS

HLR ???HSS

SGSN GGSN

MGW MGW

PSTN

Intranet/

Internet

CSCF

MGCF “IP based”

GMSC

Server

MSC

Server

Page 23: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

23Mobile

IP

Residential

Wi-Fi / WiMax wireless IMS access

PoC MessagingGLMSMultimedia

Telephony

Licensed radio IMS

PresenceCSI

WLAN Access to IMS

VCC Multimedia

TelephonyMultimedia

Telephony

IMS standardization activities

EIMS - 2014

Page 24: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

EIMS - 2014 24

Protocols related to IMS services

• Instant messaging and presence

– SIP/PoC i 3G H.324M – Video Mail (VM)

– SIP – Multimedia Messaging (MMS)

– 3G-H.324M – Multimedia advertising

• Conversational multimedia services

– SIP/PoC – Push-To-Talk (PTT) over Cellular (PoC)

– SIP i 3G-H.324M – videotelephony and videoconferencing

• Video streaming

– SIP 3G-H.324M (based on DTMF video portals)

– RTSP (IP TV, monitoring)

• Multimedia games

– SIP/JSR-180 (J2ME)

– SIP/PoC

Page 25: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

3GPP IMS architecture

25

control

transport

Visited network Home network

P-CSCF

HSS

S-CSCF BGCF MGCF

MGW

PSTN

H.248

SIP

SIP SIP

SIP ISUP/IP

AS

Diameter

IP core

network

Access

network

PCM

I-CSCF

Diameter

SIP

Diameter

�HSS – Home Subscriber Server

�CSCF – Call Session Control Function

�BGCF – Breakout Gateway Control Function

�MGCF – Media Gateway Control Function

VoIP – RTP – transport of media streams

Service plane

Control plane

Transport plane

SGW ISUP/MTP

EIMS - 2014

Page 26: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

EIMS - 201426

IMS layers: transport, session control, applications

Transport/user layer

Application layer

Control layer

S-CSCF

HSS

SIP AS SIP AS

MRFC

B-GW

SIP Diameter PSTN

RTP

I-CSCFP-CSCF

MRFP

H.248 / MEGACO

Parlay ASCAMEL

CSE

OSA GW IM SSF

Parlay API CAP API

ISC interface

Page 27: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

EIMS - 2014 27

Three layer architecture of IMS (1/3)

• Unified architecture that supports a wide range of services enabled by the flexibility of Session Initiation Protocol (SIP)

• Transport and Endpoint Layer

– Initiates and terminates SIP signaling to set up sessions and provide bearer services such as conversion of voice from analog or digital formats to IP packets using Real time Transport Protocol (RTP)

– Provides the media gateways for converting the VoIP bearer streams to the PSTN TDM format.

– The media server provides many media related services including conferencing, playing announcements, collecting in-band signaling tones, speech recognition, speech synthesis, etc.

Page 28: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

EIMS - 2014 28

Three layer architecture of IMS (2/3)

• Session Control Layer

– Call Session Control Function (CSCF)

• provides the registration of the endpoints and routing of the SIP signaling messages

to the appropriate application server

• interworks with the transport and endpoint layer to guarantee QoS across all

services

– Home Subscriber Server (HSS) database

• maintains the unique service profile for each end user

• By centralizing this information, applications can share information to create

unified personal directories, multi client type presence information and blended

services.

– Media Gateway Control Function (MGCF)

• Interworks SIP signaling with the signaling used by the media gateway

Page 29: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

EIMS - 2014 29

Three layer architecture of IMS (3/3)

• Application Server Layer

– Contains application servers, which provide the

end-user service logic

• Telephony Application Server

• IP Multimedia – Services Switching Function (IM-SSF)

• Supplemental Telephony Application Servers

• Non Telephony Application Servers

• Open Service Access – Gateway (OSA-GW)

Page 30: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

EIMS - 2014

30

IMS architecture

UE

P-CSCF I-CSCF S-CSCF

BGCF MGCF

HSS

Visited network Home network

AS

Gm

Mw

ISC

Mj

Mi

MRF

Cx

Sh

<SIP>

<DIAMETER>

<SIP>

<SIP>

Page 31: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

EIMS - 2014 31

Terminal - User Equipment (UE)

• SIP UA

• Establishes GPRS PDP context for

– signaling

– media transport

• ISIM for authentication

– Public and Private User identity

– User Network address

– Security algorithms and keys

– At least USIM

• Corellation of session control with QoS reservation

Page 32: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

EIMS - 2014

32

IMS components

UE

P-CSCF I-CSCF S-CSCF

BGCF MGCF

HSS

AS

Gm

Mw

ISC

Mj

Mi

MRF

Cx

Sh

<SIP>

<DIAMETER>

<SIP>

<SIP>

Home networkVisited network

Page 33: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

EIMS - 2014 33

Proxy Call Session Control Function - P-CSCF

• P-CSCF (Proxy Call Session Control Function)

– entry point of user terminal into the IMS world

– acting as an outbound/inbound SIP proxy server

– an IMS terminal communicates with a single P-CSCF during the registration

– establish IPsec security associations toward the IMS terminal

– verify the correctness of SIP request sent by the IMS terminal

– compressor and a decompressor of SIP messages

– may include PDF (Policy Decision Function) to authorize media plane

– generate charging information

Page 34: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

EIMS - 2014

34

IMS components

UE

P-CSCF I-CSCF S-CSCF

BGCF MGCF

HSS

AS

Gm

Mw

ISC

Mj

Mi

MRF

Cx

Sh

<SIP>

<DIAMETER>

<SIP>

<SIP>

Visited network Home network

Page 35: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

EIMS - 2014 35

Interrogating Call Session Control Function

(I-CSCF)

• A SIP proxy located at the edge of an administrative

domain

• The address of the I-CSCF is listed in the DNS records

of the domain

• I-CSCF has an interface to the SLF and HSS and route

the SIP request to the appropriate destination

(typically S-CSCF)

Page 36: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

EIMS - 2014

36

IMS components

UE

P-CSCF S-CSCF

BGCF MGCF

HSS

AS

Gm

Mw

ISC

Mj

Mi

MRF

Cx

Sh

Visited network Home network

I-CSCF

Page 37: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

EIMS - 2014 37

Serving Call Session Control Function S-CSCF

• S-CSCF (Serving Call Session Control Function)

– Central node of the signaling plane

– Acts as a SIP server and a SIP registrar

•Maintains binding between the user location (e.g. IP address of the terminal) and

the user’s SIP address of record (Public User Identity)

– Diameter interface to the HSS

•To download the authentication vectors of the user

•To download the user profile including service profile

•To inform the HSS of S-CSCF allocated to the user

– All the SIP signaling the IMS terminals sends and receives traverse the

allocated S-CSCF

– Provides SIP routing (e.g. translation from phone number to SIP URI)

– Enforces the policy of the network operator

Page 38: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

EIMS - 2014

38

IMS components

UE

P-CSCF I-CSCF S-CSCF

BGCF MGCF

HSS

AS

Gm

Mw

ISC

Mj

Mi

MRF

Cx

Sh

Visited network Home network

Page 39: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

EIMS - 2014 39

Breakout Gateway Control Function (BGCF)

• Selects PSTN/CS domain to forward a call

– local MGCF

– another BGCF

• MGCF selection process not defined

– configuration

– TRIP or a similar solution

Page 40: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

Media Gateway Control Function (MGCF)

• Gateway to PSTN

– SIP - PSTN mapping

– Establishes appropriate bearer capabilities

– Transcoding

– Acts as UA (registration not required)

EIMS - 2014 40

Page 41: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

EIMS - 2014

41

IMS components

UE

P-CSCF I-CSCF S-CSCF

BGCF MGCF

HSS

AS

Gm

Mw

ISC

Mj

Mi

MRF

Cx

Sh

Visited network Home network

Page 42: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

EIMS - 2014 42

Media Resource Function (MRF)

• Supports conference services and announcements

• Multimedia Resource Control Function (MRFC)

– Interprets information from S-CSCF andAS

• e.g. conference reservation

– controls MRPF

• Multimedia Resource Processor Function (MRPF)

– Sets bearer capabilities based on MRFCrequests

– Mixing and distribution of media

– Media streaming for user interaction

• Uses H.248 (MEGACO)

MRFC

MRPF

SIP

H.248

Media

Page 43: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

Interworking with PSTN – PSTN/CS Gateway

• PSTN/CS = MGCF + SGW + MGW

• MGCF (Media Gateway Control Function)

– ISUP-SIP mapping

– MGW control for media transcoding

– Selection of I-CSCF for calls to PSTN

• SGW (Signalling Gateway Function)

– Supports interworking between SS7 and MGCF

– Transport of ISUP messages in SIP messages to MGCF MGCF (SIP-T or

BICC)

– ISUP/BICC/MTP – ISUP/BICC/SCTP/IP

• MGW (Media Gateway)

– Termination of media streams

• RTP - PCM

• AMR - G.711 EIMS - 2014 43

Page 44: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

BGCF - Breakout Gateway Control Function

• SIP server – routing based on telephone numbering

– Using of info delivered by TRIP protocol

• IMS – PSTN/PLMN calls

• Selection of an interworking network

• Selection of an appropriate PSTN/CS gateway (MGCF) if

interworking refers to the same network in which BGCF is

located

EIMS - 2014 44

Page 45: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

EIMS - 201445

Application Server (AS)

• An SIP entity that hosts and executes

services

• Four modes of operation:

– AS acting as terminating UA, or redirect

server

– AS acting as originating UA

– AS acting as a SIP proxy

– AS performing third party call control/

B2BUA mode

• ISC - SIP Interface to S-CSCF

• Implemetation variants of ASs

– SIP AS

– OSA-SCS (Open Service Access-Service Capability

Server)

– IM-SSF (IP Multimedia Service Switching Function)

S-CSCF

AS

ISC

1

2 3

4

Page 46: IP Multimedia Subsystem Part 1 - Instytut Telekomunikacjimareks/eims/EIMS-1-bw.pdf · the services delivered to the end-user – rapid service creation without requiring standardization

EIMS - 2014 46

Implementation variants of IMS AS

CSCFS-CSCF

SIP Application

ServerSIP AS

HSSHSSOSA service

capability server

(SCS)

OSA servicecapability server

(SCS)

IM-SSFIM-SSF

Camel Service

Environment

CAMEL Service

Environment

OSA

application OSA AS

ISC

Cx ISC

ISC

CAP

MAP

Parlay OSA API

SCIM

Sh

Si

MRFCMRFC

Mr

AS AS

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Parlay OSA application servers – third parties

Online &Offline

Charging (ECF, CCF)

Service Delivery Platform

(Application server) Parlay App 1

Service Platform Trigger PointsParlay API (MPCC, MMM, Presence, Charging ...

SIP Interface

HSS

S-CSCF

S

P

T

SPT Filtering criteria

ISC

SIP

SIP-Server

Sh =

Diameter

Cx =

Diameter

Ro + Rf =

Diameter

Diameter

Parlay X GWParlay App 2

Parlay App 3

Parlay X App 1Parlay X App 2

Other access

networks

Source: T. Magedanz (TU Berlin / Fraunhofer FOKUS)

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48

IMS components

UE

I-CSCF

BGCF MGCF

HSS

AS

Gm

Mw

ISC

Mj

Mi

MRF

Cx

Sh

Visited network Home network

I-CSCF S-CSCF

AS

MRFI-CSCF

AS

P-CSCF S-CSCF

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Home Subscription Server (HSS)

• HSS (Home Subscriber Server)– Technically, an evolution of the HLR

– Central repository for user-related information• location information

• security information (authentication and authorization)

• user profile information (the services that the user is subscribed to)

• S-CSCF allocated to the user

• SLF (Subscriber Location Function)– Simple database that maps users’ addresses to

HSSs

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HSS – Home Subscriber Server

I-CSCF S-CSCF

Mw

SLF

Dx Cx

HSS AS

Cx

SIP

SIPDiameter

Sh

ISC

Diameter

GPRSaccess

MAP

SIP

Mw

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The first registration

UAR: User-Authorization-Request

UAA: User-Authorization-Answer

MAR: Multimedia-Authentication-Request

MAA: Multimedia-Authentication-Answer

SAR: Server-Assignment-Request

SAA: Server-Assignment-Answer

RAND: Random challenge

AUTN: Network Authorization Token

CK: Ciphering Key

IK: Integrity Key

13. UAR

1. Register

Visited network Home network

P-CSCF

2. Register

UA I-CSCF HSS

3. UAR

4. UAA

S-CSCF

Selection of r S-CSCF

5. Register

6. MAR

10. 401 UnauthorisedRAND||AUTN

12. RegisterRES

7. MAA

RAND||AUTN||XRES||CK||IK

9. 401 UnauthorisedRAND||AUTN

11. Register

RES

Authenticationvector selection

8. 401 Unauthorised

RAND||AUTN

14. UAA

15. RegisterRES

22. OK

20. OKCK||IK

21. OK

CK||IK

Authentication

18. SAR

19. SAA

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Home Network of Mobile A Home network of Mobile B

HSS - A

I-CSCF - A S-CSCF - A

HSS - B

S-CSCF - B I-CSCF - B

P-CSCF - A

Network Visited by Mobile A Network Visited by Mobile B

P-CSCF - B

Mobile A Mobile B

Call Control

11

22

33

4 4

5 5

Example: registration

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Control

Bearer

Visited network

of callee

Home network of called userHome network of

calling user

Visited network of callerP-CSCF

HSS

S-CSCFSIP

SIP

Diameter

P-CSCF

AS

HSS

S-CSCF SIPAS

SIP

Diameter

I-CSCF

Diameter

DNS

Packet

CoreAccess Access

SIP INVITE1

1

Retrieving user’s profile2

2

3

3 Execution of a service scenario

Resolution of User B home network address and

INVITE forwarding

4

4

Identification of Registrar for user B and INVITE forwarding5

5

Retrieving user’s profile 6

6

7

7 Execution of a service scenario

INVITE forwarding to do User B 8

8

Ringing / Alerting10

10

SDP session negotiation /

Reservation of resources

9

9

RTP

Answer / call active11

11

IMS users session

Packet

Core

SIP UESIP UE

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Home Network of Mobile A Home network of Mobile B

HSS - A

I-CSCF - A S-CSCF - A

HSS - B

S-CSCF - B I-CSCF - B

P-CSCF - A

Network Visited by Mobile A Network Visited by Mobile B

P-CSCF - B

Mobile A Mobile B

Call Control

1

2

3

4

5

6

7

Example 2 – IMS mobile call

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Control

Bearer

Network vizited by the caller Home network of the caller

P-CSCF

HSS

S-CSCF

BGCFMGCF

MGW

H.248

SIP

SIP SIP

AS

BGCF

SIP

SIP

PSTN

ISUP

Diameter

Packet

Core

Access

SIP INVITE1

1

2 3

Selection of access to PSTN and selection of MGCF4

4

ISUP IAM7

75

Seizing of a link/trunk and determination of MGW capabilities5

PCM

SDP session negotiation / Reservation of resources6

6

RTP stream

Ringing / Alerting8

8 9

Answer / Connect9

IMS to PSTN call

Retrieving user’s profile 2

3 Execution of a service scenario

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P-CSCF - A

Network Visited by Mobile A

HSS - A

I-CSCF - A S-CSCF - A

BGCF - A

Home Network of Mobile A PSTN

MGW - B

MGCF - B

Mobile A

Gateway

Control

User Profile

User Profile

1 2

3

4

5

Call to PSTN (CS domain)

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IMS Session Setup and Control

• Happens after user registration (and authentication!)

• Goals of IMS session setup

– Capability and media negotiation (e.g. codecs, port numbers, addresses)

– Network resource reservation and the support of QoS preconditions

• Additional functions performed by the IMS during the IMS Session Setup:

– Routing to the terminating IMS (= the IMS of the B-Party)

– Routing / Breakout to the PSTN / CS-Domain when the B-Party is not in the IMS, but in the PSTN / CS-Domain

– Service Control / Invocation of Application Servers to trigger the execution of Originating- and/or Terminating IMS Services

– Integrity/Confidentiality Protection of SIP Messages

– QoS/Media Authorization

– SIP Signaling Compression

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IMS Session Setup and Control 1/4

Source: T. Magedanz (TU Berlin / Fraunhofer FOKUS)

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IMS Session Setup and Control 2/4

Source: T. Magedanz (TU Berlin / Fraunhofer FOKUS)

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IMS Session Setup and Control 3/4

Source: T. Magedanz (TU Berlin / Fraunhofer FOKUS)

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IMS Session Setup and Control 4/4

Source: IMS Tutorial -T. Magedanz (TU Berlin / Fraunhofer FOKUS)

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EIMS

Project is co-financed by European Union within European Social Fund62EIMS - 2014