Danar Barzanji Marcel K Steffen Roger TröschDanar Barzanji Marcel K Steffen Roger Trösch Ferien(s)pass OberengadinIP Multimedia Subsystem # 2 Table of Content Introduction Components

22.06.2006 | Communication Systems | IMS

Danar BarzanjiMarcel K SteffenRoger Trösch

www.packetizer.com

Ferien(s)pass OberengadinIP Multimedia Subsystem

# 2

Table of Content

IntroductionComponentsArchitectural CharacteristicsConceptsProtocolsService ExamplesDiscussion

ToC


# 3

Definition of IMS

Introduction

IMS = IP Multimedia Subsystem

Standardised (3GPP) Next Generation Network(NGN)

It supports data, video, SIP-based VoIP and non-SIP packetised voice calls


# 4

3GPP

Introduction

3rd Generation Partnership Project (3GPP)It co-operates with

- ETSI (European Telecommunications Standards Institute Europe)

- ARIB/TTC (Association of Radio Industries and Business / Telecommunication Technology Committee - Japan)

- CCSA (China)- ATIS (Alliance for Telecommunications Industry Solutions -

North America)- TTA (Telecommunication Technology Association – South

Korea)Frequently releases of standardization documents (current Release 7)


# 5

Evolution of Mobile Networks

Introduction

1G – First generation wireless telephone technology (analog) e.g.: NATEL C (1987)

2G – Second generation wireless telephone technology (digital) e.g.: GSM 900/1800 (1992)

2.5G – 2G with packet switched domain e.g.: GPRS

3G – Third generation technology e.g.: UMTS


# 6

Components

ComponentsSource: Cisco: Cisco Service Exchange Framework: Supporting the IP Multimedia Subsystem, Cisco, http://www.cisco.com.


# 7

Call Session Control Function (CSCF)

Proxy-CSCF- fist point of contact for user equipment

- functions: security, verification, policy decisions

Interrogating-CSCF- contact point within operator‘s network

- functions: forwarding requests, response to S-CSCF, topology hidding of home network

Serving-CSCF- central point of signalling

- handles registration and service requests

Components


# 8 Components

Databases HSS & SLF

Source: Cisco: Cisco Service Exchange Framework: Supporting the IP Multimedia Subsystem, Cisco, http://www.cisco.com.


# 9

Databases HSS & SLF

Home Subscriber Server- central repository of all data of subscriptors

- required for session establishing & providing services

- contains: identification-, security-, location- and userprofile information

Subscription Locator Function- obtains queries about users‘ addresses

- provides requestor with all related information

Components


# 10

Interworking Elements



# 11

Interworking Elements

Breakout Gateway Control Function (BGCF)- only used from IMS originated calls into a CS domain- can report account information and collect statistical

information

Media Gateway Control Function (MGCF)- protocol convertion and mapping of SIP between IMS

and CS domain

Signaling Gateway (SGW)Media Gateway (MGW)

Components


# 12

Application Server



# 13

Application Server

Components

The application servers offer multimedia services

Three different AS categories:

- SIP AS: SIP based multimedia applications

- OSA-SCS (Open Service Access – Service Capability Server): offers functionalities like call control, user interaction, user status etc

- IM-SSF (IP Multimedia Service Switching Function): allows to use services that were designed for GSM


# 14

Media Resource Function



# 15

Media Resource Function

MRF provides home network with source of media

Media Resource Function Controller (MRFC)- interprets SIP signalling from S-CSCF for creating and

scheduling ad-hoc conference sessions and alter conference members

Media Resource Function Protocol (MRFP)- enables manipulation in connectivity layer

- performs mixing of incoming streams, media streamsource and media stream processing

Components


# 16

Support Entities



# 17

Support Entities

Policy Decision Function (PDF)- responsible for policy decisions

- decisions based on session and media relatedinfromation

Topology Hiding Inter-network Gateway (THIG)- signalling-based hiding of configuration, capacity and

topology of the network from the outside

Security Gateway (SEG)- tunnels data in encapsulated security payloads (ESP)

- is part of the network domain security

Components


# 18

Access Entities



# 19

Access Entities

Components

Possibilities to access an IMS:

GRPS / UMTS access: using Serving GPRS Support Node (SGSN) and Gateway GPRS Support Node (GGSN)

WLAN access: using Wireless LAN WirelessAccess Gateway (WLAN WAG) and Wireless LAN Packet Data Gateway (WLAN PDG)

DSL access: using Digital Subscriber Line Access Mulitplexer (DSLAM) and Base Station (BAS)


# 20

Architectural Characteristics

Architecture

The basic requirements to achieve the fundamentalIMS idea are:

Support of IP Multimedia Sessions

Support of Quality of Service (QoS)

New charging arrangements

Access independence

Support of interworking and roaming


# 21

IP Multimedia Session

Architecture

IPv6 as the basic protocolIPv6 – IPv4 interworking

Example of an IMS access in case of roaming

Source: Poikselkä, M.; IP Multimedia Concepts and Services in the Mobile Domain, John Wiley & Sons, 2004


# 22

Quality of Service

Architecture

Problem: Standard internet has delay and lost / disordered packets --> problem withvoice / videocall

Solution: Reservation of sufficient resources for each service / user.

In the case of roaming: Service level-agreements (SLA) are required


# 23

Charging (1/2)

Two different chargingmethods:

Online charging: real-time interaction with user’s account

Two different methods: Event charging & session charging

Architecture

Source: Poikselkä, M.; IP Multimedia Concepts and Services in the Mobile Domain, John Wiley & Sons, 2004


# 24

Offline charging: charging progress starts when a service has stopped

Charging (2/2)

ArchitectureSource: Poikselkä, M.; IP Multimedia Concepts and Services in the Mobile Domain, John Wiley & Sons, 2004


# 25

Access Independence

Architecture

Different possibility to access an IMS:

GPRSUMTSCDMA2000WLANWiMAXDSLCableCircuit-switched networks (PSTN, ISDN)


# 26

Interworking / Roaming

Architecture

IMS guarantees interworking between

PSTNISDNGSMOther technologies not developed by the 3GPP

User can connect to their Home-IMS in visitednetworks


# 27

Concepts

Registration

IMS Entry Point

Private/ Public Identity

IMS Identity Module (ISIM)

Security

Connectivity to non-IMS User

Concepts


# 28

Registration

Concepts

Poikselkä, M.; IP Multimedia Concepts and Services in the Mobile Domain, John Wiley & Sons, 2004


# 29

IMS Entry Point

DHCP‘s Domain Name System (DNS)- DHCP query to IP connectivity access network

- relay to DHCP server

- returns either list of SIP server domain names orSIP server IPv6 addresses of P-CSCFs

GPRS method- PDP context request to SGSN

- relay to Gateway GPRS Support Node (GGSN)

- returns IP address of entry point

Concepts


# 30

Private/ Public Identity

Private Identity:- defined by home network

- unique network access identifier (NAI)

- securely stored in IMS Identity Module (ISIM)

- only used for registration, not for SIP messages

Public Identity:- can be published

- either form of SIP URI (e.g. [email protected]) or tel URI (e.g. +41441234567)

Concepts


# 31

UICC

IMS Identity Module (ISIM)

Part of Universal Integrated Circuit Card (UICC)

Contains six different submodules:

Concepts

Security keys

Public user identity

Access rule reference

Private user identity

Home NW domain name

Administrative data

ISIM


# 32

Security

Security Key (shared by ISIM & AUC)

IP-based traffic using IP security (IPSec)

Security Gateway (SEG) for transfer between twosecurity domains with encapsulated security payload (ESP)

SIP protected with transitiv trust domains

Concepts


# 33

Connectivity to non-IMS User

MGCF performs mapping of SIP to the callcontroll in CS networks

MGW translates the two different protocols

ConceptsPoikselkä, M.; IP Multimedia Concepts and Services in the Mobile Domain, John Wiley & Sons, 2004


# 34

Protocols

Protocol categories

SIP (Session Initiation Protocol)

Use of SDP in SIP

Use of SIP in IMS

IMS-Media Plane Protocols

Authentication and security protocols

Protocols


# 35

Protocol Categories

Protocols can be classified in three categories:

Signalling or session control protocols- SIP

Media plane protocols- RTP and RTCP

Authentication and security protocols- Diameter

Protocols


# 36

SIP (Session Initiation Protocol)

An application layer signalling protocol that defines initiation, modification and termination of interactive, multimedia communication sessions between users.(IETF RFC 2543 Session Initiation Protocol)

Core protocol in IMS network

Protocols


# 37

SIP Properties

Text-based protocolExtensible protocol

- Adding new headers

Based on Request-response transaction modelSession types:

- One-to-one voice call

- One-to-many multimedia conference

Peer-to-peer protocolMessages use either UDP or TCP

Protocols


# 38

SIP User-Agents

SIP Servers

SIP Gateways

SIP-Architecture and Components

Protocols

Voice over IP IETF Standard SIP, Datus AG, 2004


# 39

SIP User Agent

An application that initiates, receives and terminatescalls

User Agent Clients (UAC) – An entity that initiates a call

User Agent Server (UAS) – An entity that receives a call

Both UAC and UAS can terminate a call

Protocols


# 40

SIP Servers (1)

Proxy Server:

intermediate entityreceives a SIP request, forwarding or responding to the requesthas access to a databasetwo types:

- Stateless Proxy (I-CSCF, no memory of any request or response)

- Stateful Proxy (P-CSCF performs stateful proxy)

Protocols


# 41

SIP Servers (2)

Redirect Server- Redirects SIP requests to UA

- Maps address into zero or more new addresses and return them to UA

Registration Server- Accepts REGISTER requests

- May support authentication

- S-CSCF performs this functionality

Protocols


# 42

SIP Gateways

An application, that interfaces a SIP network to a network utilizing another signalling protocol

Protocols


# 43

SIP Messages-Methods and Responses

SIP Responses;1xx - Informational Messages.2xx - Successful Responses.3xx - Redirection Responses.4xx - Request Failure Responses.5xx - Server Failure Responses.6xx - Global Failures Responses.

SIP Methods:INVITE – Initiates a call by inviting user to participate in session.ACK - Confirms that the client has received a final response to an INVITE request.BYE - Indicates termination of the call.CANCEL - Cancels a pending request.REGISTER – Registers the user agent.OPTIONS – Used to query the capabilities of a server.

Protocols


# 44

SIP Headers

SIP borrows much of the syntax and semantics from HTTPA SIP messages looks like an HTTP message –message formatting,header and MIME support.

-----------------------------------------------------------------SIP Header

-----------------------------------------------------------------INVITE sip:[email protected] SIP/2.0Via: SIP/2.0/UDP 192.168.6.21:5060From: sip:[email protected]: <sip:[email protected]>Call-ID: [email protected]: 100 INVITE

Accept: application/sdpContact: sip:[email protected]:5060Content-Type: application/sdp

Protocols


# 45

SIP Addressing

The SIP address is identified by a SIP URL in the format: user@host

Examples of SIP URLs:- sip:[email protected]

- sip:[email protected]

- sip:[email protected]

Protocols


# 46

Use of SDP in SIP

SDP (Session Description protocol)- Describes the media content of session- Content contains:

• IP Address• Port number• Media type• Media encoding schema

Default message type in SIP is application/sdp

Protocols


# 47

Use of SIP in IMS (1) - new parameters

IMS defines extensions to headers and parameters to address specific needs

- Auth-param for WWW-authenticate- Tokenized-by for carrying encrypt/decrypt

string- icn-charging-info for P-Charging-Vector header- New parameter defined for P-Access-Network-

Info

Protocols


# 48

Use of SIP in IMS (2) P-Headers

IMS introduced several Private Headers (P-Headers) into IETF to meet telephony needs. P-Headers are optional extensions to SIP.

- P-Asserted-Identity

- P-Called-Party-ID

- P-Access-Network-Info

- P-Visited-Network-ID

- P-Associated-URI

- P-Charging-Function-Addresses

- P-Charging-Vector

Protocols


# 49

IMS - Media Plane Protocols (1)

RTP (Real-time Transport Protocol)- defines a standardized packet format for delivering audio

and video over the Internet- Layer four, or application layer- Uses UDP for transport over IP

RTCP (RTP Control Protocol)- Generates Quality of Service (QoS) statistic- performs the mapping between the RTP timestamps and a

reference a clock• important in video conferencing application

COPS (Common Open Policy Service Protocol)- To Ensure

Protocols


# 50

IMS - Media Plane Protocols (2)

COPS Common Open Policy Service Protocol

- to ensure QoS

- enables the communication of QoS and other traffic policy information between a policy server and clients

- used in Go reference point

Protocols


# 51

Authentication and security protocols

Diameter is an authentication, authorization and accounting (AAA) protocol developed by the Internet Engineering Task Force

- lets IMS devices access the HSS and then provide the necessary authentication, authorization

- provides billable communications accounting services

Protocols


# 52

Service Examples

Video Call / Conferencing

Push-to-Talk

Instant-/ Voice Messaging

Real-time Video Sharing

Interactive Applicationstelematicstech.com

Service Examples


# 53

Video Call / Conferencing

Call: point-to-point service

Conference: multi-point service- ad-hoc with SIP

- scheduled with conference policy control protocol (CPCP)

Service Examples

nokia.com


# 54

Push-to-Talk

Standard: PoC

Standardised by OMA

Like walkie-talkie

Half-duplex service

Voice packetstransmitted by RTP

Service Examples

3C.co.uk


# 55

Instant-/ Voice Messaging

Instant Messaging:- pager-mode (Release 5)

- session-based (Release 6)

Voice Messaging- content is an audio file

- faster for user

- more personal

Service Examples

microsoft.com


# 56

Real-time Video Sharing

SIP-based multimedia streaming

Peer-to-Peer service

Both circuit- and packet-switched connection

spontaneous sharingof experiences, sourroundingsand information

Service Examples

fotojive.com


# 57

Interactive Applications

Interactive gaming (over IP multimedia core)

Sharing of personal data(e.g. calendar information, contact details, etc.)

Service Examples

3gamericas.com


# 58

Conclusion

Conclusion

Advantages:- Combining the latest in technologies- Creating a commoin platform to develop diverse

multimedia- Boost margin due to extra usage of packet-switched

networks

New benefits and services:- Quality of Service (QoS)- Different charging models- IP based technology- Access independence, Interworking


# 59

http://digitalhadz.gfxartist.com/artworks/95759


# 60

Discussion 1 – Architecture

Why using a new architecture for services that arealready offered by the internet.

Discussion


# 61

Discussion 2 – Architecture

IMS integrates different networks...

Why not building a new network based on a singletechnology?

Discussion


# 62

Discussion 3 – Video calling

Do we need video calling?

What are the advantages and possible disadvantages?

Discussion


# 63

Discussion 4 – Services/ Applications

What kind of services/ applications can you imagine to use?

Discussion


# 64

Discussion 5 – PC vs. Mobile

Are you willing to game against/ or make a video call to a mobile user while you are sitting in front of your PC?

Discussion

22.06.2006 | Communication Systems | IMS

Thanks For Your Attention!

Danar BarzanjiMarcel K SteffenRoger Trösch

www.packetizer.com

Documents

Danar Barzanji Marcel K Steffen Roger TröschDanar Barzanji Marcel K Steffen Roger Trösch Ferien(s)pass OberengadinIP Multimedia Subsystem # 2 Table of Content Introduction Components