IP Multimedia IP Multimedia SubsystemsSubsystems

ByBy

Vamsee K PemmarajuVamsee K Pemmaraju

AgendaAgenda IMS ExampleIMS Example OverviewOverview Basic PrinciplesBasic Principles ArchitectureArchitecture Access, Core Networks and User databasesAccess, Core Networks and User databases Call and Session ControlCall and Session Control Service InteroperabilityService Interoperability Migrating Application to IMSMigrating Application to IMS SIP ArchitectureSIP Architecture AdvantagesAdvantages IssuesIssues Conclusion.Conclusion.

IMS Example

ANNAANDREW

COLLEAGUES

OVERVIEWOVERVIEW

The The IP Multimedia SubsystemIP Multimedia Subsystem ( (IMSIMS) standard ) standard defines a generic architecture for offering Voice Over defines a generic architecture for offering Voice Over IP (VoIP) and Multimedia services IP (VoIP) and Multimedia services

It uses a Voice-Over -IP (VoIP) implementation based It uses a Voice-Over -IP (VoIP) implementation based on a 3GPP standardized implementation of SIP, and on a 3GPP standardized implementation of SIP, and runs over the standard Internet Protocol (IP). Existing runs over the standard Internet Protocol (IP). Existing phone systems (both packet switched and circuit phone systems (both packet switched and circuit switched are supported.switched are supported.

The aim of IMS is not only to provide new services The aim of IMS is not only to provide new services but all the services, current and future, that the but all the services, current and future, that the Internet provides. Internet provides.

To achieve these goals, IMS uses open standard IP To achieve these goals, IMS uses open standard IP protocols, defined by the IETFprotocols, defined by the IETF

Designed for both wireless and wire line networks.Designed for both wireless and wire line networks.

BASIC PRINCIPLESBASIC PRINCIPLES

Access independenceAccess independence: IMS will eventually work with any network : IMS will eventually work with any network (fixed, mobile or wireless) with packet switching functions, such as (fixed, mobile or wireless) with packet switching functions, such as GPRS, UMTS, CDMA 2000, WLAN, WiMAX, DSL cable. Older circuit GPRS, UMTS, CDMA 2000, WLAN, WiMAX, DSL cable. Older circuit switched phone systems (POTS, GSM) are supported through switched phone systems (POTS, GSM) are supported through gateways. Open interfaces between control and service layers allow gateways. Open interfaces between control and service layers allow elements and calls/sessions from different access networks to be mixed. elements and calls/sessions from different access networks to be mixed.

Different network architecturesDifferent network architectures: IMS allows operators and service : IMS allows operators and service providers to use different underlying network architectures. providers to use different underlying network architectures.

Extensive IP-based servicesExtensive IP-based services: IMS should make it easier to offer just : IMS should make it easier to offer just about any about any IPIP-based service. Examples include voice over IP (VOIP), -based service. Examples include voice over IP (VOIP), Push to talk over Cellular(POC), multiparty gaming, video conferencing, Push to talk over Cellular(POC), multiparty gaming, video conferencing, Messaging, community services, Presence Information and content Messaging, community services, Presence Information and content sharing. sharing.

IMS Network (Access Independent Service Enabled)

In Release 6 of the 3GPP specifications, the IMS has been specified to be access independent. This means that the access technology used to transport user SIP messages to the IMS network does not impact the functionality of the IMS network itself. Consequently, any access can be used, examples being DSL, Cable, WLAN, GPRS, etc. This is obviously a key step in the move towards converged network architectures

IMS Services ExamplesIMS Services Examples

•Presence (Is the user available)

• Voice and Video Telephony

• Instant Messaging

• Push to talk, push to see

• Conferencing

• Gaming

• Convergence of all of the above

ArchitectureArchitectureAL comprises of application and content servers to execute value added services to the user.

SCL comprises network control servers for managing call or session set-up. It contains CSCF (Call Session Control Function) also know as SIP server.

CL comprises of routers, and switches.

IMS Access NetworkIMS Access Network

The user can connect to an IMS network The user can connect to an IMS network using various methods, all of which are using the using various methods, all of which are using the standard Internet Protocol(IP). Direct IMS standard Internet Protocol(IP). Direct IMS terminals (mobile phones, computers, ...), can terminals (mobile phones, computers, ...), can register directly into an IMS network, even when register directly into an IMS network, even when they are roaming in another network or country they are roaming in another network or country (the visited network). (the visited network).

Fixed access (e.g., DSL, Cable Modems, Fixed access (e.g., DSL, Cable Modems, Ethernet ...), mobile access (W-CDMA, CDMA, Ethernet ...), mobile access (W-CDMA, CDMA, GSM, GPRS ...) and wireless access (WLAN, GSM, GPRS ...) and wireless access (WLAN, WiMAX ...) are all supported. Other phone WiMAX ...) are all supported. Other phone systems like the POTS (the old analogue systems like the POTS (the old analogue telephones), and non IMS-compatible VoIP telephones), and non IMS-compatible VoIP systems are supported through gateways.systems are supported through gateways.

Control NetworkControl Network

The HSS (The HSS (Home Subscriber ServerHome Subscriber Server) is the master ) is the master user database that supports the IMS network entities user database that supports the IMS network entities that are actually handling the calls or sessions. that are actually handling the calls or sessions.

It contains the subscription-related information (user It contains the subscription-related information (user profiles), performs authentication and authorization profiles), performs authentication and authorization of the user, and can provide information about the of the user, and can provide information about the physical location of user. It's similar to the GSM .physical location of user. It's similar to the GSM .

An SLF (An SLF (Subscriber Location FunctionSubscriber Location Function) is needed ) is needed when multiple HSSs are used. Both the HSS and the when multiple HSSs are used. Both the HSS and the SLF implement the DIAMETER protocol (Cx, Dx and SLF implement the DIAMETER protocol (Cx, Dx and Sh interfaces).Sh interfaces).

Call or Session ControlCall or Session Control

FunctionsFunctions P-CSCF: ProxyP-CSCF: Proxy Call Session Control Call Session Control

Function:Function: This is the first point of contact within This is the first point of contact within the IMS for a User Element (UE). It ensures that the IMS for a User Element (UE). It ensures that the registration of the user is passed to the the registration of the user is passed to the correct home network and that SIP session correct home network and that SIP session messages are passed to the correct Serving messages are passed to the correct Serving CSCF (S-CSCF) once registration has occurred CSCF (S-CSCF) once registration has occurred

PDF (Policy Decision Function):PDF (Policy Decision Function): This function This function takes a service level policy request from the takes a service level policy request from the application layer (for example P-CSCF) and application layer (for example P-CSCF) and translates it into IP QoS parameters. translates it into IP QoS parameters.

IBCF Interconnect Border Control FunctionIBCF Interconnect Border Control Function:: This standard is to specify the detection of This standard is to specify the detection of failure of interconnect points.failure of interconnect points.

I-CSCF Interrogating Call Session Control I-CSCF Interrogating Call Session Control Function: Function: This is the function that is able to This is the function that is able to determine the S-CSCF (Serving-Call Session determine the S-CSCF (Serving-Call Session Control Function) with which a user should Control Function) with which a user should register. This is achieved by querying the Home register. This is achieved by querying the Home Subscriber Server (HSS).Subscriber Server (HSS).

Serving Call Session Control Function: Serving Call Session Control Function: This is This is the function that registers the user and provides the function that registers the user and provides service to them even though these services may be service to them even though these services may be on separate application platforms. on separate application platforms.

Service interoperabilityService interoperability IMS enables the reuse of inter-operator IMS enables the reuse of inter-operator

relations. Rather than develop different relations. Rather than develop different interconnect relations and agreements for interconnect relations and agreements for each service, IMS enables a single inter-each service, IMS enables a single inter-operator relationship to be established and operator relationship to be established and built upon for each service.built upon for each service.

Many functions can be reused for fast Many functions can be reused for fast service creation and delivery.service creation and delivery.

IMS services are hosted by an Application IMS services are hosted by an Application Server, they are implicitly placed in the Server, they are implicitly placed in the IMS application layer.IMS application layer.

IMS defines how service requests are IMS defines how service requests are routed, which protocols are supported etc.routed, which protocols are supported etc.

Service Architectures

Migrating applications to IMS.Migrating applications to IMS.

SIP (Session Initiation SIP (Session Initiation Protocol)Protocol)

SIP is an application layer protocol that can SIP is an application layer protocol that can establish, modify and can terminate establish, modify and can terminate multimedia sessions and conferences over the multimedia sessions and conferences over the internet.internet.

SIP messages could contain session SIP messages could contain session descriptions such that participants can descriptions such that participants can negotiate with media types and other negotiate with media types and other parameters of the session.parameters of the session.

SIP provides its own mechanisms for SIP provides its own mechanisms for reliability and can run on top of several reliability and can run on top of several different transport protocols such as TCP, different transport protocols such as TCP, UDP and SCTP (Stream Control Transmission UDP and SCTP (Stream Control Transmission Protocol)Protocol)

Establish a session between the originating and Establish a session between the originating and target end point—If the call can be completed, target end point—If the call can be completed, SIP establishes a session between the end points. SIP establishes a session between the end points. SIP also supports mid-call changes, such as the SIP also supports mid-call changes, such as the addition of another end point to the conference or addition of another end point to the conference or the changing of a media characteristic or codec.the changing of a media characteristic or codec.

Handle the transfer and termination of calls—SIP Handle the transfer and termination of calls—SIP supports the transfer of calls from one end point supports the transfer of calls from one end point to another. During a call transfer, SIP simply to another. During a call transfer, SIP simply establishes a session between the transferee and establishes a session between the transferee and a new end point (specified by the transferring a new end point (specified by the transferring party) and terminates the session between the party) and terminates the session between the transferee and the transferring party. At the end transferee and the transferring party. At the end of a call, SIP terminates the sessions between all of a call, SIP terminates the sessions between all parties.parties.

SIP ElementsSIP Elements User Agent Client / ServerUser Agent Client / Server

user agent client and server are logical entities, user agent client and server are logical entities, whose roles last only for the duration of the whose roles last only for the duration of the transactiontransaction

Proxy ServerProxy Server forward SIP requests and responsesforward SIP requests and responses

Redirect ServerRedirect Server

receive requests and then return the location of receive requests and then return the location of another SIP useranother SIP user

agent or server where the user might be foundagent or server where the user might be found

RegistrarRegistrar accept REGISTER requests and places the accept REGISTER requests and places the

information into theinformation into the location service for the domain it handles.location service for the domain it handles.

SIP ArchitectureSIP Architecture

SIP Request through a SIP Request through a Proxy ServerProxy Server

If a proxy server is used, the caller UA sends an INVITE request to the proxy server, the proxy server determines the path, and then forwards the request to the cal lee

SIP Response through a SIP Response through a Proxy ServerProxy Server

The cal lee responds to the proxy server, which in turn, forwards the response to the caller

SIP Session through a SIP Session through a Proxy ServerProxy Server

The proxy server forwards the acknowledgments of both parties. A session is then established between the caller and callee. Real-time Transfer Protocol (RTP) is used for the communication between the caller and the cal lee

InterfacesInterfaces

Click here Interfaces.htmfor Different Interfaces and their Description

Advantages Advantages The core network is independent of a particular access The core network is independent of a particular access

technology technology Integrated mobility for all network applications Integrated mobility for all network applications Easier migration of applications from fixed to mobile users Easier migration of applications from fixed to mobile users Faster deployment of new services based on standardized Faster deployment of new services based on standardized

architecture architecture An end to unique or customized applications, leading to An end to unique or customized applications, leading to

lower CAPEX and OPEXlower CAPEX and OPEX New applications such as presence information, New applications such as presence information,

videoconferencing, Push to talk over cellular (POC), videoconferencing, Push to talk over cellular (POC), multiparty gaming, community services and content multiparty gaming, community services and content sharing. sharing.

Evolution to combinational services, for example by Evolution to combinational services, for example by combining instant messaging and voice combining instant messaging and voice

User profiles are stored in a central location User profiles are stored in a central location The architecture is designed for easy scalability and The architecture is designed for easy scalability and

redundancyredundancy

Issues Issues Benefits need to be further articulated in terms of actual Benefits need to be further articulated in terms of actual

savings. savings. IMS is "operator friendly" which means that it provides the IMS is "operator friendly" which means that it provides the

operator with comprehensive control of content at the expense operator with comprehensive control of content at the expense of the consumer. of the consumer.

IMS uses the 3GPP variant of SIP, which needs to interoperate IMS uses the 3GPP variant of SIP, which needs to interoperate with the IETF SIP. with the IETF SIP.

IMS is an optimization of the network, and investments for such IMS is an optimization of the network, and investments for such optimization are questionable. optimization are questionable.

Some IMS proponents are trying to push it as the total solution Some IMS proponents are trying to push it as the total solution for IP-based systems such as IPTV, which is causing push-back for IP-based systems such as IPTV, which is causing push-back from companies wanting a much richer experience in land-line from companies wanting a much richer experience in land-line environments that don't have mobile constraints; environments that don't have mobile constraints;

There are no products available other than paper machine; There are no products available other than paper machine; The new services are the same of ISDN services, i.e, voice calls, The new services are the same of ISDN services, i.e, voice calls,

video calls, etc. All the supposed new services already exists; video calls, etc. All the supposed new services already exists; QoS is not a problem for voice calls. Skype's revenue shows QoS is not a problem for voice calls. Skype's revenue shows

that; that; Subscribers won't accept that service providers controls what Subscribers won't accept that service providers controls what

application they are running; application they are running; It's a useless control-layer. It's a useless control-layer.

ConclusionConclusion

Thus IMS plays a vital role in Thus IMS plays a vital role in transferring multimedia messages transferring multimedia messages easily.easily.

ReferencesReferences

http://en.wikipedia.org/wiki/IP_http://en.wikipedia.org/wiki/IP_Multimedia_SubsystemMultimedia_Subsystem

http://www.cisco.com/univercd/cc/td/http://www.cisco.com/univercd/cc/td/doc/product/voice/sipsols/biggulp/bgdoc/product/voice/sipsols/biggulp/bgsipov.htmsipov.htm

www.empirix.comwww.empirix.com

QuestionsQuestions

What is IMS and explain different What is IMS and explain different elements in IMS?elements in IMS?

What SIP? How call is initiated using What SIP? How call is initiated using SIP?SIP?

Differences between IMS and pre-Differences between IMS and pre-IMS?IMS?