Defining an IMS Strategy

As a set of specifications or as a set of products provided by telecom suppliers, IMS is not the answer about how to ensure a bright future for telecom operators.

Basically, IMS should be perceived as a toolkit, which can be used alternatively or successively in various manners leading to drastically different results. As a consequence, an operator needs to define a short, mid and long term strategy based on IMS that suits its business strategy, and it has to take the adequate measures to apply this strategy. Here, we are touching the biggest IMS issue. It is not technical but rather cultural, practical and organisational.

In this post, I will try to outline some potential elements of an IMS strategy.

Deploying IMS

While some operators may simply decide to deploy IMS as part of their network evolution roadmap, many require an initial motivation to take the decision to go for it.

At the time being, the main triggers for deciding to deploy an IMS network are certainly the following:

- Replacement of the legacy circuit-switched network for fixed telephony services (IMS used as PSTN emulation subsystem).

- Deployment of a carrier grade VoIP solution for fixed residential customers, possibly with mobile/fixed convergence services including or not call contuinity between fixed and cellular access (knowned as voice call continuity).

- Deployment of carrier grade enterprise services including for instance business trunking, IP centrex or fixed mobile convergence.

- Deployment of a compelling set of mobile services through the Rich Communication Suite (RCS) or something else.

- Deployment or migration of an IPTV solution making use of IMS.

- Deployment of a selected set of IMS-enabled fixed mobile services.

However, such initial motivations are not always strong enough to validate investments in IMS.

For instance, a fixed operator may wonder why it should invest in IMS to reimplement a telephony service whose revenues are rapidly decreasing and which is likely to eventually be offered for free. Likewise, the usage of IMS for a specific service like IPTV or RCS or for a specific business segment like enterprise may not be economically worth for the operator.

It is therefore necessary for the operator to have a strategy for extending the usage of IMS beyond its initial deployment scope in order to have an optimal return on investment. Such a strategy is also fundamental for the operator to decide on future investments.

More especially, any decision to eventually replace a pre-IMS service implementation (e.g. telephony, messaging, IPTV) with an IMS one may impact the investment and evolution plan for the pre-IMS implementation.

The Future of Telephony

The future of existing telephony services and their implementation is a tricky issue that needs to be addressed carefully.

Basically, IMS permits to:

- Re-implement classical telephony services for legacy terminals and narrowband access (IMS as a PSTN emulation subsystem in ETSI TISPAN)

- Implement a new generation of voice-centric telephony services for new terminals (e.g. SIP phones) and broadband access

- Implement a new multimedia communication experience, in which voice is only a media component among others, whether they are related to person to person communication (e.g. messaging, video), content (e.g. streaming video, files) or data (e.g. events, application sharing, shared browsing).

The operator needs to clearly identify these services, decide which ones it wants to deploy, how, and in which timeframe.

Once this diversity has been understood and associated decisions have been taken, the operator can start to think about the implementation of related value-added services. For instance, are or should the value added services be the same or be different for each variant? Should they be implemented on the same or different platforms?

The operator can also think, if relevant with its plans, about how these different types of voice-related services should co-exist and possibly interwork.

The relationship between IMS and classical telephony services is of particular interest. It goes beyond the question of replacing the circuit-switched core network with an IMS based IP network as the two networks will co-exist for some time, and during this transition phase the support of value-added telephony services for both may be a question in itself.

The operator may have the choice between several alternatives and decide to opt for one or to evolve from one to the other over time:

- Using different service implementations in both networks (e.g. Intelligent Network in CS and a Telephony Application Server (TAS) in IMS)

- Reusing legacy Intelligent Network solution(s) in IMS

- Re-implementing services on a new platform able to support both IN and IMS ISC interfaces

- Reusing the IMS TAS for delivering value-added services to circuit-switched voice, in replacement to Intelligent Network servers (ongoing standardisation in 3GPP as IMS Centralized Services)

The future of messaging

In mobile networks, various messaging services can exist such as SMS, MMS and IMPS (OMA standard for mobile Instant Messaging).

IMS messaging has the potential to emulate all these messaging services and to add more to the user experience. The operator may therefore have to decide if and when it wants to eventually replace all of the existing messaging services and how it wants to manage the transition phase during which IMS messaging takes off and co-exists with them.

Moreover, as for voice, the multimedia nature of IMS makes that messaging may eventually cease to exist as a standalone service and be part as a multimedia component, of a more global and powerful multimedia communication paradigm. Should the operator skip the silo IMS messaging step and go directly to the multimedia communication service or should it implement one after the other? If so, how should the migration be performed?

IMS as a multi-service platform

An important feature of the IMS service architecture is its ability to support the harmonious co-existence of multiple services related to communication, content and data. This is a discriminating feature compared to a non-IMS SIP network, which lacks a standard service architecture and requires ad-hoc and often cumbersome support for the co-existence of several services, with limited multivendorship possibilities, and this until the architecture explodes after the hack too much (as this happens with all silo architectures whose limits are pushed too much).

An advantage of using an IMS core network as a multi-service platform is its ability to factorize and make coherent such functions as service discovery, user identification, user authentication, QoS and policy control, security, detection of the access technology used by the subscriber for service adaptation purpose (e.g. UMTS vs. LTE, xDSL vs FTTH) or interworking among operators, among others.

There are important cost savings to be achieved through deploying multiple services on IMS, both in terms of simplifying service implementation and harmonizing the support of functions common to multiple services.

There can also be important benefits related to the centralized knowledged in the IMS of service usage by subscribers, like the ability to apply QoS policies that take into account the multiple services used in parallel from the same home or device.

The operator needs to prepare and plan for the gradual support of new services and the porting of existing ones on IMS. This implies, among other things, not to take architectural decisions related to IMS that are specific to one service and may prevent the deployment of new ones in the future. To take a simplistic example, an Initial Filter Criteria routing all SIP INVITEs to a TAS may work as long IMS is used to support a single telephony service. On the other hand, it can be a source of nightmare as soon as an IPTV or IMS Messaging service (both making use of INVITEs as well) is introduced.

Using IMS as a multi-service platform is not always straightforward for operators which are used to deploy silo services and whose decision processes and organizations are defined according to this paradigm. An IMS strategy may therefore include organizational and decision process changes as well.

IMS for new services

I have often read that IMS cannot support new services. This is a wrong assessment.

The versatile nature of the SIP protocol, illustrated by the invaluable concept of event packages, the ability to integrate the IMS application layer in a more global SOA (Service Oriented Architecture) and UOA (User Oriented Architecture) framework, and the possibility to strongly integrate IMS with the Internet and its services create thousands of opportunities for new services, many of which are not connected to person to person communication.

The operator needs to define a strategy related to this opportunity for innovation: whether it wants to use this opportunity, how, what changes need to be done in organizations, skills and practices.

IMS for a new user experience

Possibly more important than new services, IMS permits to create a brand new user experience which makes that the frontier between services as we know them can totally disappear.

As already mentioned above, multimedia sessions permit to deliver communication, content and data services in a combined context.

Moreover, IMS-based fixed mobile convergence has the potential of eventually making the device and access technology used by the subscriber a mere detail of service delivery. Using a converged subscription, a user could access all its services from all its device, from all access technologies (whether fixed or mobile) and with the same identity.

Such a full convergence cannot happen overnight due to various reasons related to organizations, existing business processes, cultures, regulation, and to a much lesser extent, technical issues.

The operator must therefore plan and prepare for these evolutions, defining clear steps towards a the target. For instance, the operator may initially decide to use the cost savings aspect of IMS based fixed mobile convergence, by sharing the same IMS core network between fixed and mobile subscriptions. It also must decide if and how it eventually wants to support full convergence. For instance, will the operator eventually offer only converged subscriptions or will it permit subscribers to chose between converged and non-converged subscriptions? In this latter case, what would be the implications?

Managing the complexity of the IMS application layer

This blog has often tried to describe the fantastic power of the SIP protocol and the IMS service architecture to deliver rich services.

One of the outstanding features of the service architecture is its ability to combine services or service logic components residing in the devices, in the operator's network and across different operators' networks, the Internet or Enterprise networks, in a very flexible manner.

There are basically two composition mechanisms:

- Implicit composition: device and network based service logic or services are chained in the SIP signalling path.

- Explicit composition: device and network based service logic or services make use of each other through an appropriate interface like SIP, web services, HTTP, RTSP, H.248 or another protocol.

While very powerful from a functional perspective, this potential leads to new complexity related to distribution, compared to the traditionally centralized implementation of telecommunications services.

The operator must therefore find ways to deal with this complexity by addressing issues like the definition of relevant compositio handling functions like the SCIM, the management of service composition data like Initial Filter Criterias and SCIM information, the addressing of potentially redundant or conflicting functions across different servers, or the determination of approaches to measure quality of experience or determine root causes for potential problems.

Optimizing the IMS application layer

These distribution and composition mechanisms also lead to potentially critical optimization issues.

These optimization issues may for instance relate to:

- End-to-end performance if too many physical servers are involved in service delivery. In an extreme case, a spectacular service on paper may simply be irrealistic in practice due to disqualifying delays in service delivery to the end user.

- The load of IMS entities, more especially the S-CSCF and application servers, which are essential components in service delivery and composition.

- The cost of deploying and operating services if the application layer is too heterogeneous and too distributed or if features are duplicated across multiple servers.

- The impact of the failure of a server, for instance an application server, on subscribers. For instance, how many users will be impacted by the failure of an AS and for which services?

The operator must therefore define an optimal strategy to deploy services, which optimizes the user experience while minimizing costs and risks. This issue has to deal with service platforms and service topology. For instance, IMS offers alternatives to the dedication of an application server to a certain service for a large portion of subscribers by permitting on the contrary an application server to support a variety of interdependent services for a smaller subset of subscribers.

Service Platforms

The choice of service platforms is a key component of an IMS strategy, though only one component among others.

An operator has basically the choice between two alternatives for a service platform:

- A black box delivered by a service supplier.

- An open service platform delivered by an IT vendor, usually called Service Development Platforms (SDPs) in a telecom context, on which services are applications delivered by application providers or implemented in-house by the operator.

Concerning SDPs, the operator has further choices between alternatives like IT-centric platforms (e.g. J2EE, .Net) or telecom centric ones (e.g. JAIN SLEE, OSA application servers).

Each approach has its advantages and drawbacks, and these may differ depending on the considered timeframe. The operator should therefore define criteria permitting to select the most appropriate platform for a given service in the short, mid and long term, and prepare for the potential migration from one to the other, when appropriate.

IMS clients and devices

The best package of IMS services is useless if it is not adequately supported by clients and devices.

The operator must address such key issues like:

- The distribution of service logic between devices and the network. Note that depending on the characteristics of a device (e.g. high end vs low end, mobile vs. fixed), a given service may require different implementations or implementation variants for access by different devices.

- The distribution of service logic and IMS support between different devices on the customer premises, e.g. a home gateway and end-devices.

- The management of IMS client updates to support new IMS services.

- Optimizing device management by using IMS-intrinsic benefits.

- Spreading IMS support in the wider range of devices.

- Presenting IMS services in an optimal way to end-users in order to make them attractive and make their access and usage intuitive.

Conclusion

IMS by itself is not an answer to the challenges an operator will face in the future. An operator should define a coherent strategy comprising which components of the IMS potential it wants to use, in which timeframe and how.

While many operators have already deployed IMS or are planning to do so, usually with a well defined short term objective, I have the feeling that only a few are actively working on a mid and long term IMS strategy.

This is a pity, because defining such a strategy would permit to:

- Help IMS acceptance in the company by outlining the short, mid and long term benefits expected from it.

- Anticipate on changes required in organizations, practices, and skills to apply the strategy. By doing so, speed up the implementation of the strategy.

- Have a better control of short and mid term investments, for instance by avoiding excessive investments in implementations or services whose lifetime will be shortened by the implementation of the IMS strategy.

As you may infer from this post, I have put a lot of thoughts in these topics. Do not hesitate to contact me on this.

Christophe

The Service Broker / SCIM market

The concepts of SCIM or Service Broker were introduced in 3GPP IMS specifications, but so far have never been adequately defined (I had the opportunity to address this topic several times).

However, this does not mean that there are no SCIM or Service Broker products (or product components) on the market!

Light Reading has just issued a report called Combining Telco Services: The Network Service Broker Opportunity. As they provide a list of vendors they have surveyed for their report, I decided to have a look at what these companies actually provide by looking at documentation available on their web sites. In this post I will summarize my findings, which are only based on my (potentially erroneous or biased) interpretation of usually high level product descriptions.

Call Control / IN Centric Service Broker / SCIM

Most of these products are presented as equally applicable to Intelligent Networks and IMS, which in some cases might mean that the product is an Intelligent Network one that has been upgraded to support SIP, or that the supplier hopes that what is good for IN will also be good for (telephony-centric) IMS.

As described by Aepona, their Service Broker is primarily a proxy Service Switching Function (SSF) between the switch and multiple IN servers (thus permitting service invocation in multiple servers, what a switch is usually unable to do). As an IMS "SCIM", it performs a similar function between the S-CSCF and multiple ASs. Because of its dual SIP/IN nature, the Service Broker can also serve as a gateway between IMS and IN (the "IM SSF" entity in 3GPP IMS specifications).

The description of the AppTrigger's Ignite Application Session Controller (ASC) includes a "SCIM+". Like Aepona's Service Broker, ASC sits between the network and the "application cloud". IMS is explicitly listed along legacy TDM networks that can appear below the ACS, but the figure on the web page does not show IMS at all, only entities of a fixed IP access network. The product supports Parlay X, MAP/CAMEL and SIP. It also supports SIP to IN interworking (IM SSF).

OpenCloud is the supplier of a JAIN SLEE platform, a standardized Java service execution platform that was initially targeted at new generation IN services (IN services implemented in Java on an open platform and possibly using non-call related service capabilities like location or SMS as part of their logic). Such a platform can also support SIP and Diameter interfaces and can therefore be positioned as a SIP AS platform as well. On their page, Opencloud speak about a Service Interaction SLEE (SIS) for IN, and another one for IMS. The SIS supports service interaction and composition. The SIS can also offload an IN server by supporting some IN logic itself (logic as it is based on an IN service platform).

jNetX is another supplier of a JAIN SLEE platform. I was not able to find any information about a SCIM or Service Broker on their site, but if they have one it is very likely to be similar to what Aepona, AppTrigger and Opencloud offer.

I could not find a precise description of Tekelec's TekSCIM Service Mediator. However, as it is supposed to provide a seamless experience to TDM and IMS users, and its IMS role is to manage and simplify complex service interactions, I assume this is more or less the same type of product.

These products often have a clear interest in a TDM IN context, and I think this should be the primary reason why an operator might be interested in them. On the other hand, I am more doubtful about their value in an IMS context, even for the support of telephony services, and this for the following reasons:

- An IMS S-CSCF has the capability to chain several ASs in SIP signalling, so such a feature supported by a SCIM/SB would be functionally redundant.

- Call control Service Interaction Management is an important issue that has never been addressed in a satisfactory generic manner in IN networks, more especially when implemented in a standalone box outside of application servers. Why would this change now and more especially in an IMS context?

- Unless it is used to emulate the TDM network, IMS is a very different type of network, and SIP has nothing to do with INAP or CAP. What is good and necessary for TDM is not obviously good and necessary in IMS.

- Providing added value call control services in IMS is necessary, but it is not what operators will make money with. A SCIM/SB centered around voice-centric call control is by no means the magic box that will solve all operators' IMS related problems.

- The interest of an IM SSF function is questionable. IN platforms are often old and costly, and operators often have to fully rely on the supplier of the platform for developing new services. Is it interesting for operators to extend the life of these platforms for many years by positioning them in their long term IMS strategy? On the contrary, many would prefer to replace their IN servers by new application servers able to control TDM calls as well as IMS ones, and this is exactly what the ongoing 3GPP IMS Centralized Services (ICS) initiative is trying to achieve.

TCAP / Web Services Gateway

Convergin's Accolade WCS SCIM seems to be a gateway supporting translation between TCAP and web services. It is not clear to me if this is only this and if it is limited to TCAP (leaving the task of supporting CAP, MAP or INAP to the application) or if it also supports a direct translation of these protocols to web services.

The first thing to say is that this does not correspond at all to what someone can expect from a product called "SCIM".

The second thing to say is that, whether the name is appropriate or not, this component can be very interesting in an IMS context, when it is associated to an IP-centric service platform, which lacks native support of legacy SS7-based protocols to access legacy service capabilities in the TDM network. This is typically the case of J2EE platforms supporting SIP servlets for IMS, which are offered by well known companies like IBM, Oracle or Sun.

These platforms are ideal to implement innovative IMS applications which can combine usage of SIP, HTTP, Diameter and web services, thus permitting convergence between the Internet, Enterprise IT and the new Telco domains. So far, the lacking capability has been the possibility to conveniently connect with the legacy TDM telco world (OSA/Parlay gateways have not proved to be simple and cost effective enough).

I do not think that such a product would allow a J2EE server to become a suitable platform to implement classical IN services. On the other hand, they could permit to implement new TDM-centric services that make use of IMS enablers like presence or instant messaging, or IMS-centric services that need to use TDM capabilities like starting a pure TDM call.

Consequently, this is not a surprise if Convergin seems to be in business with the J2EE suppliers I mentioned.

SIP-level Orchestration Engine

This is the approach adopted by suppliers of J2EE platforms (IBM, Oracle/BEA, Sun?), which usually clearly distinguish between the need to orchestrate web services, using a standard like BPEL, and the need to orchestrate services invoked through SIP requests. Differences may lie in both semantical and performance aspects.

In this context, the SCIM/SB corresponds to the concept of application router, defined in JSR 289, the latest SIP servlets specification. The original mechanism specified for invoking SIP servlet applications, based on servlet mapping rules that are quite similar to web servlet mapping rules in the fact that they rely on a quite simplistic analysis of incoming SIP messages, has proved to be inadequate for a proper selection and composition of IMS services hosted by a J2EE platform. The application router permits to replace the servlet mapping rules by an intelligent component tailored to the needs of the operator.

The intelligence itself is not standardized, and this is therefore an important differentiation area for suppliers or for operators who may decide to specify and possibly implement their own application router.

The service invocation and chaining logic may take into account subscription information (which services the user is subscribed to) as well as other information related to the user, such as presence, service preferences (e.g. the user wants this service to be executed at certain times) or calendar information.There might also be more or less sophisticated rules related to the composition of services.

The ideas for a SCIM I exposed on this blog fit in this context, with the concern to remain as simple as possible and avoid too much intelligence, complexity and processing delays in this component. I think that the suppliers of J2EE platforms are trying to offer the possibility for more sophisticated rules, adding both more potential and more risks to the concept.

Global Orchestration Engine

This seems to be the case for the Alcatel-Lucent Service Broker, implemented by Bell Labs, which is part of the Alcatel Lucent Service Delivery Platform (SDP). The component supports both SIP and web services interfaces, and examples given illustrate access to user subscription information, service preferences, presence, as well as access to other services like IPTV through web services.*

This Service Broker therefore seems to be an integrated equivalent to the combination of a web services orchestration engine and a SIP application dispatcher as proposed by J2EE suppliers.

A potential reason for this difference is that Alcatel Lucent provide their own SIP servlets container, which is a standalone component that needs to be integrated with a third party J2EE platform for converged services. The service broker would therefore permit integration with J2EE web containers (integration which is much tighter in J2EE platforms supporting both web and SIP servlets) and would transfer web services orchestration to the Alcatel Lucent SIP-centric component as well.

Such an approach might offer advantages, more especially in terms of performance, but could also come with associated complexity, a lack of compliance to web services orchestration standards, and the gain obtained through a tighter integration of different orchestrations may also lead to less flexibility for the operator. However, this would be an aspect to investigate.

Service Management Mediation

Leapstone's CCE ServiceBroker is a tool that applies both to legacy networks and IMS. It aims at making easier the management and provisioning of packaged services, including subscriber management and live management of composition and interaction rules between blended services.

From an IMS perspective, this means that the operator may use serviceBroker to define service composition rules and to generate appropriate data for an HSS (Initial Filter Criteria) and a SCIM, as well as for other network databases.

As such, ServiceBroker appears to be a management complement associated to what is usually called a SCIM or Service Broker. More generally, this is a service and subscriber management mediation tool as can already be found on the
market, but enriched with IMS-specific service composition requirements.

Such a tool is very important but also requires ad-hoc adaptations in order to fit in specific environments, considering that management interfaces are usually vendor-specific. Concerning the SCIM/SB, this is even worse as this component is not standardized and leaves room for very different implementations, as can be seen in this post.

Other SCIMs / Service Brokers

Considering the list provided by Light Reading, I was not able to find anything about the Ericsson and Huawei implementations of the concept.

Conclusions

The concept of SCIM / Service Broker, which is part of IMS specifications but has never been specified, leaves room to multiple interpretations and very different products claiming this label can be found on the market.

You can basically find two mainstream interpretations:

- The SCIM / SB is a standalone component that takes care of classical call control and IN issues related to the support of multiple application servers and complex interactions between call control services. The concept is primarily aimed at legacy networks and is also promoted as being equally applicable (and important) for IMS. The telephony context is clear and while everyone can have its own opinion on the interest of such a product for IMS, I will assume that no-one can seriously claim that this component will help an operator finding new sources of revenue with IMS (the key term here is "leveraging", applied to TDM and IMS in the context of telephony).

- The SCIM / SB is a component part of a service delivery platform, and its aim is to complement what the IMS core network component called S-CSCF can do for the composition and "blending" of several services. Such a SCIM / SB can be specialized in SIP-level orchestration (a dedicated engine will do the equivalent for web services) or can address both SIP and web services orchestration.

The first interpretation is closer to the initial motivation for introducing the concept in 3GPP specifications, while the second is closer to what the real IMS need actually is.

A major architecture difference between the two interpretations is that the first one is a standalone product standing between the IMS core network and application servers, while the second is an added-value component of a more comprehensive product usually called service delivery platform in the telecom context (an application server in its own right).

The description I made of a SCIM on this blog is essentially one of the second category. However, since then I thought a little bit about what a standalone SCIM / SB could be, in the terms of which value it could provide to a SCIM / SB embedded in a service platform can do.

I cannot divulge here the content of these thoughts, as they are being discussed with a customer company of Arismore, but to make it short I think there is a lot of added-value a standalone SCIM / Service Broker could add to a service platform -embedded one, while being very different from what the market has to offer right now. More especially, such a product would have no relationship to IN and call control.

If you are knowledgeable in some of the products I surveyed in this post, do not hesitate to contact me in order to correct or complement it. I will gladly compile and post feedbacks, including those that make a point against my assertions.

Christophe

Course on the IMS Application Layer

Through my company Arismore, I am offering a 2-day course on the IMS application layer. It can be delivered either in French or in English (all the material is in English). There are sessions regularly organized in my company's premises in Saint-Cloud, Paris, France, which are open to individuals. The course can also be delivered on site, within or outside Europe.

What makes this course unique is that, while others usually provide a litteral description of IMS specifications and essentially concentrate on the IMS core network, largely overlooking the IMS service architecture, sometimes even delivering misleading information, this one totally concentrates on this domain in which resides the true potential of IMS for differentiation and revenue generation (both for operators and suppliers). You can take this course after a regular IMS one, but my experience shows that even IMS novices can follow it without missing any core network background.

The course does not only describe IMS application-related specifications that span multiple standardization organizations (3GPP, the IETF, OMA, ETSI TISPAN). It also helps understanding what lies behind them, by providing revealing insights on how they were produced (e.g. historical timeline, assumptions, mistakes, conflicts between companies, need to address specific issues), shows in details how they effectively work, explains how they can optimally be exploited to deliver innovative services or innovatively deliver existing ones, and finally addresses the main opportunities and challenges that IMS brings to the industry. After this course, the student can understand what IMS can deliver, why there exist so many conflicting perceptions of IMS, and why IMS is as much a challenge as a promise.

Several on site sessions have been given or are planned in the near future, and the response has been so positive that these sessions usually lead to discussions about further collaboration between the customer company and Arismore.

Contact me at cgourraud@yahoo.ca if you are interested in either an on site session or in a session organized in our offices in Paris (planned dates can be found in the side bar of the blog).

Here follows a description of the course. You can also request from me a slightly more detailed powerpoint content description.

Part 1: The IMS Service Architecture

This is the most comprehensive part of the course. It addresses several objectives: understanding how the IMS service architecture works (dynamic view), getting an overview of the specifications (static view), understanding the drivers behind standardization decisions (motivations, design by accident, pending issues), understanding how the architecture can be used (application layer architecture, service patterns).

Standardized topics include:
- Overview of the architecture
- IMPUs & PSIs
- ISC usage scenarios & examples
- Details of ISC
- Service profiles and initial filter criterias (iFCs)
- OSA SCS / IM SSF / SIP AS
- MRFC/MRFP
- SCIM & Service Broker
- IMS Communication Services
- User Data Management (Sh, OMA XDM, GUP)

The service features of SIP are treated as a specific topic. It highlights the potential of the protocol when used in IMS or in other networks:
- Multimedia sessions
- Event packages
- Routing alternatives (SIP forking, callee capabilities/caller preferences), GRUUs)
- Support of Group Services
- Combination with other protocols (content indirection, SIP REFER, SIP session, body in SIP message)
- Interoperability aspects (between SIP profiles, between SIP and other protocols)

Service oriented features specific to the IMS service architecture, and complementing the intrinsic SIP ones are also detailed. This part permits to understand the value IMS adds on other SIP-based networks:
- Service composition
- Logic mutualization
- Personalization / Differentiation of user experience
- Simple access to services
- Service flexibility / agility
- Authorization to services
- Unlimited service scalability
- Multi-vendorship / Differentiation for each service
- Service anthropomorphism
- Usage of a single identity for multiple services

Part 2: IMS standardized services and enablers

This part covers IMS services and enablers standardized or under standardization in 3GPP, OMA and ETSI TISPAN. As for Part 1, background information about the standardization process is given.

User data services & enablers:
- Presence (IETF, 3GPP, OMA specifications)
- Group Management / Group Services

Voice oriented services & enablers:
OMA Push To Talk Over Cellular (Poc) V1 and V2
3GPP Combining circuit-switched and IMS services (CSI)
3GPP Voice Call Continuity (VCC)
3GPP/TISPAN Multimedia Telephony (MMTel)
3GPP IMS Centralized Services (ICS)
3GPP Conferencing

Messaging services & enablers:
OMA SIP Push
Messaging (IETF IM, 3GPP IMS Messaging, OMA SIMPLE IM)
3GPP SMS over generic IP access
OMA Converged IP Messaging (CPM) - Messaging part

Multimedia services & enablers:
OMA Converged IP Messaging (CPM) - Multimedia part
TISPAN IPTV

This part ends with a description of the Rich Communication Suite (RCS) initiative

Part 3: Opportunities & Challenges

This final part addresses essential topics which go beyond IMS specifications.

It is structured around the following topics:
- Fixed Mobile Convergence (from technical to user oriented convergence: opportunities and challenges)
- Which role(s) for the operators (e.g. bitpipe provider, intelligent pipe/channel provider, service provider with more or less control)
- Exploiting IMS Capabilities (e.g. User Oriented Architecture, Distributed Service Architecture, need for optimizing the IMS service architecture)
- Service Platforms (e.g. black boxes vs. open platforms, JAIN SLEE, J2EE)
- IMS as a service integration framework (different types of IMS services, how to integrate non-IMS services into IMS, relationship to 3rd party service providers)

Christophe

3GPP Communication Services

In the past, I had the opportunity to write three posts (here and there and there) about the 3GPP concept of Communication Service. These posts were written in the heat of possibly major IMS-defining decisions being taken, in order to warn about some risks related to some options. Time has passed and the concept is now (nearly totally) specified in IMS. In this post I will describe Communication Services and how they can be used by operators.

Definition

According to TS 23.228, "an IMS communication service is a type of communication defined by a service definition that specifies the rules and procedures and allowed medias for a specific type of communication and that utilises the IMS enablers."

Examples of Communication Services are OMA Push To Talk over Cellular (PoC) or OMA SIMPLE Instant Messaging (also called IMS Messaging in 3GPP specifications).

In other words a Communication Service is a set of communication media and the rules that govern the possible (i.e. permitted) transactions between them. For instance, OMA SIMPLE Instant Messaging only permits SIP sessions to include messaging components. Trying to upgrade a messaging session into a voice session is not part of the OMA SIMPLE IM service, and can be considered as a violation of the OMA SIMPLE IM Communication Service.

A Communication Service is identified in SIP signalling through an IMS Communication Service Identifier (ICSI). The format as well as an example of ICSI can be found in TS 24.229:urn-xxx:3gpp-service.ims.icsi.mmtel (Multimedia Telephony).

An IMS application can use a Communication Service to be delivered to the end-user. For instance, an application could push content to a user by using the OMA SIMPLE IM Communication Service. Such an application can be identified in SIP signalling through an IMS Application Reference Identifier (IARI) for which TS 24.229 also provides an example: g.3gpp.app_ref="urn%3Aurn-xxx%3A3gpp-application.ims.iari.game-v1". Note that IARIs are only meaningful for IMS clients and are totally ignored by IMS core network entities. This is why I will not mention them much in the following.

The list of Communication Services associated to a user is provisioned in the service profile of the user in the HSS. This list is used by the S-CSCF for its processing of SIP requests. It is also provisioned in IMS clients for usage.

The IETF draft describing the necessary SIP extensions to support the concept of Communication Service states that all the information required for a network to understand the service requested by a user should be derivable from the SIP request (e.g. by looking at the SDP and the request-uri in a SIP INVITE), without the need for an explicit identifier like an ICSI. It accordingly states that the ICSI is a way for the network to save computational resources required to inspect the SIP request. I would tend to disagree with this analysis. First, the ICSI does not only define how a user wants to start the session, it also explicitly defines that the user will not try or may not be allowed to later renegotiate the session in a way that is not specified by the service definition. Moreover, an IMS S-CSCF will not make the economy of analyzing the request, as it will have to ensure that the ICSI and both the initial and subsequent INVITEs in the session are coherent one with the others. Therefore, the usage of Communication Services will rather increase the need for computational resources in the S-CSCF than lower it.

What Communication Services could have been

The company which introduced the concept of Communication Service in 3GPP had a quite radical proposal of how it would be used:
- The usage of a Communication Service would have been mandatory in all SIP requests initiated by an IMS client. A side-effect was that all IMS applications would have had to rely on a Communication Service, thus strongly limiting opportunities for IMS services.
- Two SIP clients would not have been able to set up a session together if they did not share the same Communication Service. This would have implied that a client supporting OMA SIMPLE IM and a client able to support both messaging and voice within the same SIP session would not be able to establish a session together, even if they shared a common media component permitting to communicate. This would also have implied that a SIP client without any knowledge of IMS-specific ICSIs would not have been able to set up sessions with an IMS client.
- Usage of Communication Services totally relied on the IETF-specified Contact and Accept-Contact headers (in which ICSIs and IARIs would have been included as media feature tags), thus using a standard IETF header in a non-standard way and adding to interoperability issues with non-IMS SIP clients.

Would have they been accepted, these proposals would have raised important barriers to service innovation in the IMS domain, and would have caused huge interoperability problems between IMS and non-IMS clients, de facto creating a walled garden out of IMS.

A side effect is that the concept would have created a two-tiered IMS application layer, with application servers supporting (standardized) Communication Services at the bottom, and application servers supporting applications making use of Communication Services at the top. The lower tier would typically have consisted of standardized services implemented as black boxes supplied by classical network equipment suppliers, and the (rather power-less) upper tier by open platforms provided by IT suppliers (more or less what you can find in a pre-IMS telecommunications network, with OSA/Parlay usually defining the frontier between the two layers). This two-tiered architecture would have been reproduced within IMS clients.

However, in their current state, due to the involvement of the IETF and the consensus imposed by companies which did not endorse this original view, 3GPP specifications are quite far from this.

General benefits of Communication Services

Communication Services can be useful to all operators, even if their strategies clearly differ, as long as each operator has options about how it wants to use them. Representing an operator, I had in the past the opportunity to discuss the issue with the supplier promoting the concept. After expressing my concerns about it and hearing their arguments in its favor, I told them: "Communication Services are fine with me as long as, as an operator, I can use them when I see an interest for it and not use them when I do not see any". Since then, this possibility to use Communication Services a la carte is what has been specified.

These usage options start at the IMS client, which may but is not mandated to insert an ICSI (and possibly IARI) in a SIP request it generates. They also exist further in the processing of SIP signalling by the IMS core network, as you will see below.

But first, let us consider the aspects of Communication Services that may appeal to all operators.

Communication Services can make the life of operators easier in some aspects.

Put a label on a service, transport this label end-to-end in SIP signalling, and you get a practical handle for charging (more especially when several operators and/or transit network suppliers are involved in the end-to-end communication), QoS and policy control, and to set your initial filter criteria for involving ASs supporting the service. However, this does not mean that the IMS core network should ease on its processing. For instance, current IMS specifications permit to charge a session based on both accounting information related to SIP signalling (e.g. this is a messaging session with a beginning and an end) and media level information (e.g. this is indeed messaging that goes through). It would be risky for an operator to assume that because an ICSI states that the session is about messaging and messaging only, this is actually the case. If so, Communication Services could be a great weapon for fraud.

The usage of ICSIs in users' service profiles to determine the routing to application servers can be of great interest as I will illustrate now. Imagine that an IMS client initiates an INVITE for messaging while the operator has deployed OMA IM SIMPLE, OMA CPM and OMA PoC V2, which all may start with such an INVITE. The operator may face the tricky challenge to decide to which application server the request should be routed in the case where the user is subscribed to at least two of these services. By placing an ICSI identifying the service it wants to use, the IMS client indicates to the network that this is this service and not this one that it intends to use.

Passed these basic, different handling of communication services are possible, which map to different strategies.

The two sections below describe these potential differences. What is common between both is that an IMS client may insert an ICSI in a SIP request it generates, but this is not a mandatory standard procedure. When a client wants to use a communication service (and possibly a specific application making use of it), it inserts the ICSI in a header called P-Preferred-Service. It may also include the ICSI and IARI in Accept-Contact headers (currently 3GPP is not clear about the exact procedure for this).

Communication Services for advanced user control

The S-CSCF serving a user (the originating one for requests initiated by the user, the terminating one for requests received by the user) may be mandated to insert an ICSI in all the requests it receives. For doing so, it compares the request with the list of ICSIs provisioned in the user's service profile for a match. This ICSI is inserted in a P-Asserted-Service header created by the S-CSCF. In the case where the IMS client created a P-Preferred-Service header, it is removed by the S-CSCF, and it is possible that the ICSI inserted by the S-CSCF and the original ICSI are different. The S-CSCF will also insert an ICSI in SIP requests which did not have any P-Preferred-Service header.

When an ICSI inserted by a user does not match the request (e.g. the user inserted an OMA SIMPLE IM ICSI and actually has an SDP body for a voice session) or the ICSI in the SIP request is not in the list of authorized ICSIs in the user's service profile, or the S-CSCF cannot map the request to any of the ICSIs authorized for the user, the S-CSCF may simply reject the request.

Once a SIP session has started, the S-CSCF may also reject renegotiations of the session that do not correspond to the service definition (e.g. a user tries to upgrade an OMA SIMPLE IM session to voice).

More liberal usages of Communication Services

An operator may inhibit all the restrictive behavior of the S-CSCF by not provisioning any ICSI in the service profile of a user. In this case, an IMS client can still insert an ICSI in a SIP request (the ICSI may have been provisioned in the client or may be hard-coded) and the ICSI may still be used to route the request to an application server, for charging, QoS or policy control, but the S-CSCF cannot insert an asserted ICSI and reject any request. Note that such an ICSI cannot be trusted by the core network but an AS can be used for this purpose.

If an operator provisions ICSIs in the service profile of the user, it can still decide that the S-CSCF should not reject requests as in the specification this decision is left to the operator's policy. The S-CSCF will just insert the P-Asserted-Service header.

Finally, even if the most restrictive S-CSCF behavior could apply, its potential impossibility to unambiguously associate one ICSI to a request (e.g. the user is authorized to use an OMA SIMPLE IM and an OMA CPM ICSI while both services can start with a messaging session) mandates it not to insert any ICSI in the request, de facto inhibiting its restrictive processing.

Interoperability with non-IMS cients

The IETF solved the potential interoperability issues between IMS and non-IMS clients by clearly discriminating between, on the one hand the usage of ICSIs and IARIs in the SIP Accept-Contact and Contact headers, which comply with the IETF procedures for a SIP client to declare its capabilities to a network (so-called callee capabilities) and for a SIP client to indicate preferences or instruct a SIP network about how the request it generated should be routed/forked (so-called caller preferences), and on the other hand the usage of ICSIs for network-centric usage within an IMS network (definition of two 3GPP specific headers: P-Preferred-Service and P-Asserted-Service).

Based on 3GPP procedures, a non-IMS client may receive a SIP request from an IMS client that includes a P-Asserted-Service header, but this header will simply be ignored and will not impact processing in the non-IMS client.

ICSIs and IARIs populated in the Accept-Contact header do not create interoperability problems either, as this header can (optionally) be used by a client to help selecting an application to be contacted but is primarily aimed at SIP proxies, instructing them about how to route the request.

However, there might still be a case where an IETF-compliant usage of Accept-Contact may prevent an IMS client to initiate a session with a non-IMS client: if the Accept-Contact header that includes the ICSI or IARI also includes both the "explicit" and "require" parameters, it instructs the SIP proxy not to route the request to a SIP client that did not explicitly declared its support of the ICSI (or IARI). As non-IMS clients are very likely not to being even aware of IMS ISCIs and IARIs, the IMS client would never be able to set up a session with them (however, the funny thing is that a non-IMS client would be able to set up a session with an IMS one).

At the moment, 3GPP did not decide on how ICSIs and IARIs should be used in Accept-Contact, but the risk I just mentioned is explicitly stated as a note in TS 24.229, which indicates that some companies are very wary about the issue. In any case, there is a need to clarify this aspect, and this might have to be done either globally (e.g. an IMS client shall not use these two parameters for ICSIs, but it might use them for some IARIs if the corresponding application requires it), or service per service, unless it is left to the decision of the operator.

Potential issues with ICSIs

To be used for advanced control, ICSIs require additional provisioning in the service profile of the user (HSS) as well as in IMS clients.

ICSIs now make the S-CSCF service aware, as it has to be able to compare ICSIs to SIP requests and SDP bodies into session initiation and session re-negotiation requests. At best this may imply a reconfiguration of the S-CSCF each time a new communication service is introduced (standardized or operator-specific). At worst this may imply an upgrade of the S-CSCF.

The S-CSCF processing of ICSIs (checking if a request matches the ICSI in it, trying to find an ICSI for a request without any, checking if session renegotiation matches what is permitted for an ICSI) will add to resource consumption and end-to-end delays. In the case where ICSIs do not significantly simplify other procedures of the IMS core network (and I do not think they will), this is a pure loss for core network characteristics. This might be a minor factor, but it could also be an important one once IMS traffic grows in important proportions.

Any future for Communication Services used for control?

In its current state of specification, the concept of Communication Service can be used both by liberal operators and by operators wishing to exert a strong control over their customers.

In the liberal approach, ICSIs can be used to facilitate the routing of service requests to the right application server(s). No constraining behavior of the S-CSCF will be mandated, and while ICSIs can be used as a convenient way to identify a service (for instance in charging records), they will not significantly help the task of core network entities in their processing (e.g. generating accurate charging records).

In the controlling approach, ICSIs can be used as a means to check that users only access (typically silo) services they are explicitly authorized to use, and that they cannot escape control (at least at SIP level) during the session.

Maybe the controlling approach will be used by some operators. However, considering the facts that ICSIs do not only come with benefits and that users may be led to draw comparisons between operators with a strong controlling and a more liberal approach, I am not sure right now that Communication Services are promised to a bright IMS future. Future will tell.

Christophe

References:
Definitions and requirements: TS 23.228 chapter 4.13
Detailed procedures by IMS client: TS 24229 chapters 5.1.1.2.1 (declaration of supported ICSIs as callee capabilities at registration), 5.1.2A.1 (generation of SIP request), 5.1.2A.2 (reception of SIP request)
Detailed procedures by S-CSCF: TS 24.229 chapter 5.4.3.2 (originating requests), 5.4.3.3 (terminating requests)
Communication Services in Service Profiles: TS 29.228 Appendix B (B.2 and B.2.1A)

IMS Service Anthropomorphism

Anthropomorphism is the attribution of uniquely human characteristics and qualities to nonhuman beings, inanimate objects, or natural or supernatural phenomena (wikipedia).

The pictures taken from various cartoons by Tex Avery that you can see at the top of this post illustrate an anthropomorphic behavior associated to animals.

Service anthropomorphism is therefore the possibility for an IMS service to behave and be treated as a human user of the IMS network. This post describes how IMS supports service anthropomorphism and what an anthropomorphic service can do and benefit from.

Symetric usage of SIP between IMS users and IMS services

The IMS service architecture ensures that every SIP request that is generated or processed by an IMS client can also be generated or processed by an IMS application server.

For instance, if an IMS client can generate a SIP instant message, set up a SIP session, or subscribe to the presence of another user, an IMS application server can do it as well.

Conversely, if an IMS client can receive a SIP instant message, process a SIP session set up request or process a SUBSCRIBE to any SIP event package (e.g. presence), an IMS application server can also do as well.

An interesting consequence of this feature is that the concept of enabler (the possibility for a service to use a remote feature) is simple to implement in an IMS network, and can be extremely powerful.

In a traditional telecommunications architecture, some services offered to an end-user can also be used as an enabler by an application server. This is the case for network-based user location in a mobile network, which can accessed in a location server from both a device and an application server hosting location-based services. However, in most cases, the user to service interface and the service to service interface are different, and both need to be specified and implemented for the application to be used as both an end-user service and an enabler by other services. In IMS, as soon as a service is deployed in the network, for which a SIP based interface has been defined for access by IMS clients, the exact same interface can immediately be used by other IMS application servers to access the service as an enabler for their own services. In theory and when it makes sense from a service perspective, every new IMS service can become an enabler for other services, which themselves can become enablers for other services. There is therefore a high potential for an explosion of service opportunities each time a new IMS service is deployed in the network.

Another difference with a traditional telecommunications network is that, in such a network, a service enabler is always network-based. As devices are more or less stupid, every added-value logic that can serve other services is located on a server in the network. On the other hand, with IMS, every logic processing SIP requests can theoratically be located both in IMS clients and in IMS application servers. While complex logic (e.g. full-featured presence) will tend to be located in powerful IMS ASs, simpler logic can be located in the IMS client and be accessed by an AS through SIP. For instance, IMS clients can support SIP event packages (using SUBSCRIBE, NOTIFY, PUBLISH) that are able to inform and notify ASs about what is located or is happening in the IMS client: session states, information located in device, information or status about a specific device-based application like a game. This implies that, with IMS, the concept of enabler is extended from the network to the endpoints, and this offers potentially huge service opportunities.

Finally, in a traditional network a service and the enabler it accesses are most of the time located in the same operator's domain, as addressing, request routing and security issues are important barriers to overcome for inter-operator interfaces. In an IMS network, SIP routing procedures cross boundaries between networks with secured interfaces, and the addressing of SIP enablers is based on public identities like IMS Public User Identities (IMPUs) and Public Service Identities (PSIs). This implies that, technically, a presence based service from one operator can access the presence of a user subscribed with a different operator (or located in the Internet, but then with security risks).

In an IMS network, all SIP requests originate from a public identity (IMPU, PSI) and are addressed to a public identity (IMPU, PSI). How do IMS application servers fit in this picture?

Service impersonating a user

An IMS AS can process requests addressed to an IMPU of a user it serves, and can generate a SIP request on behalf of a user, by placing an IMPU as the originator of the request it (the AS) actually generates.

For instance, an AS hosting session control logic for a user can receive the INVITEs addressed to an IMPU of this user and serve it on its behalf (e.g. accept or reject the session). In another example, IMS presence requests are always addressed to an IMPU of the user from which the presence is sought. In theory, this request could and should be routed to one or several IMS clients associated to the user, but in practice they are all routed to a network-based AS serving presence requests on its behalf.

In yet another example, consider a service that decides on the best way to route messages issued by user A. Possible alternatives include IMS messaging to the same IMPU, IMS messaging to another IMPU, SMS, MMS, email, or an Internet IM service. When user A issues an IMS message to user B, this message is routed to the AS supporting the advanced routing function. This AS can then extract the IMPU of user B from the IM, and generate a presence request originated from user A and addressed to user B. This request will reach the presence server of user B, possibly in another network, which will apply authorization rules associated to user A and generate an appropriate response. This response may provide information to the service about the messaging alternatives available for user B, as well as the associated addresses, preferences, and reachability. It can therefore select the most appropriate approach to deliver the message to user B. In this use case, it is very important for the advanced routing service to endorse the identity of user A, because it acts on its behalf and must benefit from the exact same information as user A would.

This means that an IMS service can act as a network-based agent or proxy of a user (and here I do not mean "SIP User Agent" and "SIP Proxy").

Service acting as itself

A service can also receive requests addressed to a PSI that identifies itself, or generate a request using its own PSI as the originator.

This may permit a service to communicate with a user ("Hey, I am your voicemail") or to benefit from privileges associated to a service (e.g. when the service generates a presence request to a presence server located in the same domain, it has full access rights and top priority toward all users' presence information).

Group Management

Group management permits a user (or an operator) to regroup a set of URIs (SIP or others) into a set which is identified and addressable via a PSI. Such a group PSI can then be used in SIP requests, which then automatically become group requests through appropriate support in IMS application servers. For instance, an IM addressed to a group will be exploded to individual IMs sent to each member of the group, a presence request to a group will be decomposed into individual presence requests, and an INVITE to a group will automatically start a conference. Groups can also be utilized within application servers to define, e.g. black or white lists.

An IMPU and a PSI have the exact same formats (either a SIP URI or a TEL URI).

This means that groups of services identified by a PSI can be defined, as well as groups mixing IMPUs and PSIs. Consequently, everything that can be made towards user groups can also be made towards service groups and service/user groups. For instance, conference session setup can relate to groups including both human beings and automatons like a media server.

Associating services to services

There exist several approaches to route a SIP request addressed to a PSI to an AS serving this PSI. Most approaches rely on a direct mapping between the PSI (SIP or TEL URI) and the address of a server. They differ by where the mapping is defined (DNS, HSS), constraints on how the PSI URI is constructed, and where the routing is performed (originating S-CSCF, I-CSCF).

One approach is different, and while the IMS specifications never describe what it permits, its potential is much more significant from a service perspective. It lies in the association of a service profile to the PSI in the HSS, the same way service profiles are associated to IMPUs, which permit the routing of SIP requests associated to the IMPU to IMS application servers. With this approach a PSI is provisioned in the HSS like an IMPU, except that not all information need to be provisioned (e.g. no need for authentication information).

A first interest of this approach is that not all requests addressed to a PSI have to be routed to the same server. Some requests might be routed to one and others to another, based on initial filter criteria in the PSI service profile.

A very interesting feature of this approach, which is not related to service anthropomorphism, is that if an IMS user decides to make a user group consisting of the members of its family, identified by a PSI like sip:MyFamily@operator.com, an INVITE addressed to the PSI might be routed to a conferencing server, a MESSAGE addressed to the same PSI to an IM exploder, and a SUBSCRIBE to the PSI to a resource list server (in order to explode the request toward each member and compile the results in a single NOTIFY). Compare to the other approaches, which will route requests addressed to sip:MyFamily@operator.com to a single server, actually forcing the user to define a different PSI for each service it would like to apply to its family if it wants different services to apply (e.g. sip:MyFamily@conferencing.operator.com). This need to define a specific SIP URI for a combination group/service is also the way you will have to proceed in a non-IMS SIP network. This is an interesting example of how IMS can add value over non-IMS SIP networks and make the life of a user easier.

To come back to the subject of this post, let us consider a streaming service for a live event like a concert. An IMS user will typically start viewing the event by generating a SIP INVITE to a PSI identifying the live event. With service profile based SIP routing, the operator could define that a SUBSCRIBE to the presence event package would be routed to a presence server instead of the streaming media server (to which INVITEs will be routed). This would permit to associate presence information to the live event, like a description of the live event, information on how to subscribe to it, and status information (delayed, not started, starting, started). A user subscribing to the live event's presence could then be automatically be notified about when it can start viewing it.

In effect, associating a presence to the live event is associating a service to it, the same way presence can be a service associated to a user.

But there are other ways to associate a service to a service. Service profile -based routing permits to chain different services in the SIP signalling path. Consider an anti-spam application the operator proposes to its IMS customers. Every message addressed to the user can be routed to this application to be analyzed and possibly blocked. Now consider a discussion forum based on IMS messaging. The name of the forum is identified by a PSI (e.g. sip:TheIMSLantern@operator.com) so that each IM addressed to the forum is distributed to all the users currently registered with it. Service-profile based PSI routing would permit the operator to route a SIP request addressed to the forum first to the anti-spam application, then to the forum server. This is as if the discussion forum was treated as an IMS user subscribed to the anti-spam service. Now extend this example with an anti-virus application and an archive server, or think of other examples.

To conclude...

An IMS service can be anthropomorphic because it can act like a user, it can act as a network-based agent of the user, it can interact with other services like a user, it can communicate with "other" users, and it can be associated to other IMS services just like a user.

Note that "IMS service anthropomorphism" is not a standard or a commonly used term. I created it. You might therefore want to be careful and cite your source if if decide to use the term in discussions or in documents.

Christophe

Different Strategies for IMS

Most operators do not want to be reduced to the role of bitpipe provider, offering low cost connectivity to services supplied by other companies. They want to be service providers themselves, and try to figure out how IMS will help them achieving this objective.

This basic point aside, the strategies between operators might diverge, and their differences may essentially lie into the level of control they want IMS to support. This level of control can be illustrated by the following questions, which purposedly address extreme attitudes (it should be understood that intermediate opinions also exist).

Should IMS be fully open to other IP networks, and permit communication and service interoperability with devices and service providers located outside of the traditional telecommunications domain, more especially the Internet? Or should IMS, on the contrary, help operators establishing a new "walled garden", forcing or strongly encouraging the customer to use the services provided by telecommunications operator, and preventing or strongly discouraging them to use services provided in the Internet?

Should IMS foster service innovation, permitting telecommunications operators to differentiate between themselves and compete on value for money to improve their market share? Or should IMS, on the contrary, be used to maintain the old, slow and standardization driven telecommunications model, in which most operators provide the same mass market services and only differentiate at the margin?

Operators in a challenger position, or which are confident in their ability to cope with the new challenges they are facing with the rapid evolution of technologies and customers' habits, are keen on adopting an open IMS and a new approach to service creation. In addition to developing their own services, they are likely to seek other ways to maximize revenues, acting as a channel provider or intelligent pipe provider towards 3rd party service providers, by partnering with them and/or adding values to their services (see here an example of how IMS can be used by an operator to add value to 3rd party services).

Operators with a control freak approach are more in a defensive attitude, having to preserve a market position or facing internal uncertainties about the future world.

These diverging strategies do not only concern operators, as they will directly impact the supplier ecosystem the operators will rely on in the years to come.

Operators favoring service innovation, short development cycles, high service customization, or niche market services, will have to adopt technologies and practices that come from more dynamic business sectors, where state-of-the-art IT and methods are common place. To develop their services, they are likely to rely on open service platforms (e.g. J2EE), enterprise architecture practices, and to primarily view services as applications, developed in-house, purchased off the shelf, or contracted to IT-centric application providers.

On the other hand, operators opting for mass market standardized services, with little differentiation, are likely to maintain the existing ecosystem of traditional equipment and service box suppliers. The more a traditional telecommunications equipment supplier has difficulties to move from telco IT (e.g. proprietary platforms, poor skills at Java, SOA and other advanced IT architecture and programming paradigms, long and costly development cycles) to standard IT, the more this supplier will take as a threat the advent of an all-IP and open IMS era.

How IMS positioned itself a couple of years ago

This was a mixed bag.

Despite what some people think and claim, 3GPP always ensured that IMS was fully interoperable with non-IMS SIP networks. I already addressed this topic in a past post, from which I will only reuse a telling example: IMS session setup.

In order to permit IMS calls to replicate the experience an end-user has when establishing a call in the circuit-switched network, IMS opted for a more complex procedure than the basic IETF SIP one, permitting network resources to be reserved before the call is established. An IMS device is mandated to follow this procedure. While this procedure and the related SIP extensions can also be used in non-IMS networks (these are not 3GPP-specific extensions), it cannot be assumed that all SIP clients will ever support it. Not doing anything about this would have prevented an IMS device to set up sessions with most of non-IMS devices. However, 3GPP did something about this: in case the peer device does not support the complex session setup procedure, the IMS device (or a network based agent acting on its behalf) is mandated to revert to the basic IETF procedure.

The technical ingredients to support service innovation were also there: the intrinsic power of IP and SIP, the powerful IMS service architecture, the SIP servlets specification permitting the integration of SIP-related service logic into advanced and open J2EE platforms, the endorsement of SIP servlets by all the suppliers of J2EE platforms.

However, it did not work out that well, and this can be linked to multiple good and bad reasons: IMS was still a prospective technology (real deployments are starting now), focus was on short-term (hopefully) value generation services (e.g. VoIP, push to talk over cellular), IT-centric platforms were not mature yet, the capabilities of SIP and the IMS service architecture were not well known, no compelling IMS services were proposed, the legacy telecom culture was a handicap that was reflected in the old fashioned silo way OMA (the Open Mobile Alliance) was specifying IMS-based enablers...

I would not claim that all these factors have disappeared now, but some progress has been made in the recent time, as IMS is becoming real.

The last two years: hidden fight between various strategies

3GPP Communication Services are the textbook example of how suppliers and operators with conflicting strategies have used all the subtle (and less subtle) panoply of standardization tricks to push their agendas and counter-agendas in IMS standardization.

I already addressed the topic (here and there) at a time when the fight reached its heights, and I will soon dedicate a post to describe the current status and potential consequences of Communication Services standardization.

For now, suffice to say that:

- Would all the ideas pushed by Communication Services promoters have been accepted, IMS would certainly have become a walled garden preventing interoperability between IMS and non-IMS SIP devices, and huge barriers to innovation by IMS operators would have been erected.

- In the present state of standardization, these risks have been globally averted (thanks to the IETF and some companies active in 3GPP).

I personally view Multimedia Telephony as an initiative that goes in the same control direction. As I already wrote, Multimedia Telephony can be seen as an attempt at defining multimedia sessions as an incremental, person-to-person communication centric evolution of voice telephony. Moreover, at the moment, the content of Multimedia Telephony specifications is limited to the emulation of classical voice telephony services over an IMS network. From this you can derive that, from a target perspective, MMTel is a half full or half empty evolution in direction of the true multimedia experience SIP can provide, and that in any case there is not much hurry to move toward this target.

Another initiative I would strongly liken to MMTel is OMA PoC phase 2. While PoC phase 1 can be described as a 2-party or group walkie talkie service (essentially) for mobile phones, PoC phase 2 significantly enriches the user experience with other media, permitting for instance to transform a session from half duplex voice (original PoC) to full duplex voice, to use text messaging or send images, files or video streams in the session. This is still not full multimedia, but a controlled step in the direction, defined as an enrichment of a service silo looking for a future. As such a silo, PoC has a very interesting feature for companies which are not that thrilled with the idea of interworking with non-IMS devices: PoC is the only IMS service that can be described as fully IMS centric. It was totally specified by the IMS community and has no equivalent in the non-IMS SIP community.

On the other side of the fence, you can undoubtly place the ongoing OMA Converged IP Messaging (CPM) initiative. CPM intends to use the full capabilities of SIP sessions and IMS convergence features. It is multi-access, multi-party, multi-media in the most advanced meaning, and multi-device, supporting both person-to-person and person-to-service sessions. If every thing goes well, instead of a fully standardized service like telephony or PoC, CPM should end up being an architectural framework permitting operators to place or allow any media component one can think of in an IMS session, thus realizing (and possibly improving on) everything one can implement in the Internet using the SIP protocol.

Until recently, I tended to see 3GPP as the standardization body with the most coherent and liberal approach to IMS, and OMA as the organization which, through its heavy pre-IMS heritage and its inadequate organization, would keep on standardizing good old service silos (with overlapping features). However, it looks like this time is over, at least for OMA. This said, thinking about it, this OMA organizational problem (the fact that each group standardizing a service works in parallel to the others while the architecture group works on its own topics instead of ensuring the overall coherency of the OMA architecture like SA2 does in 3GPP) is more obvious than ever when you consider the current situation of OMA specifications: as an operator, you now have no less than three alternatives if you want to deploy an IMS messaging solution, OMA SIMPLE Messaging, OMA PoC phase 2 and OMA Converged IP Messaging, among which the last two can claim to support multimedia sessions as well. Finally, I may withdraw my positive comment about OMA as a whole.

Christophe

IMS Standardization Tracking Report

Tracking the standardization of IMS in 3GPP is a difficult and time consuming task. There are so many working groups involved (e.g. SA1, SA2, SA3, CT1), and so many meetings.

I recently came across Hughes Systique Corporation, a Consulting, Development and System Integration company Headquarted in the US,
which seems to be doing a lot of interesting work in the IMS, Web 2.0 and convergence of the same. Of the various other things they offer, they produce
an 'IMS Standards Tracking report' which is sent out to their clients once in two months and keeps readers updated on new technology updates
in various 3GPP forums, including in IMS-WiMAX interworking. There is an annual subscription at an affordable cost.

Arjun , who is responsible for the IMS & Converged Applications practice in the company contacted me recently and emailed me
a copy of one of their reports to see. He told me, in addition to the report, they also offer free conversations with the key analysts who prepare it. This is a 100% technology
report and not a market one, therefore serving a niche that was missing. With the recently uptake on IMS, Arjun believes this report will be a very cost effective solution for companies
who cannot afford to travel or track 300+ 3GPP CRs in each meeting.

I encourage you to have a look at it. If your company decides to subscribe to the report, please let HSC know that you got the information from The IMS Lantern.

For more details on this report see: http://www.hsc.com/IMSConsulting/index.aspx
For their IMS blog, see: http://www.hsc.com/IMSConsulting/Insight.aspx
For Arjun's personal IMS (and other VoIP/SIP/2.0) blog: http://iconverged.wordpress.com/category/3gpp/

Christophe