IMS for Enterprises

1. IMS for Enterprises IEEE Commun. Mag. pp. 68-75, July 2007 H. Khlifi, DialexiaJ.-C. Gregoire, INRS-EMT

2. Outline • Introduction • Overview of IMS Architecture • Requirements of Enterprise Communication • Service Models for Enterprise IMS • IT Integration • Conclusion

3. Introduction • IMS enable SIP-based communication services with more features and flexibility than CS network service. • IMS was adopted by ETSI and TISPAN for PS in fixed networks and cable-based communication systems. • The enterprise market has not been addressed.

4. Overview of IMS Architecture • P-CSCF • Contact point for User • Registration • S-CSCF • Registration • Service Connection • Billing • AAA • Service Triggering Info. • User Profiles • I-CSCF • Edge of AD • DIAMETER-based Cx / Dx for user location (SLF/HSS)

5. Overview of IMS Architecture (cont.) • HSS • User profiles (subscription-related information) • AAA • SLF: subscriber location function • DIAMETER protocol (Cx, Dx, Sh)

6. Overview of IMS Architecture (cont.) IMS messages <-> OSA messages AS: • SIP-AS • Core network value-added service • ISC: IMS Service Control • OSA-AS • Open Services Arch. • External IMS Service • OSA-SCS: OSA service capabilities server • CAMEL-AS • Customized Appl. Mobile-Enhanced Logic • For GSM • IM-SSF: IMS Service Switching Function CAMEL appl. part messages

7. Overview of IMS Architecture (cont.) • AAA • IMS Subscriber identity module (ISIM) in UMTS Integrated Circuit Card (UIUC) • Authentication and Key Agreement (AKA) • In TISPAN, AKA model is embedded in TISPAN terminal, TISPAN residential gateway, or a split device (USB device).

8. Requirements of Enterprise Communication • For enterprise, the IMS framework for service delivery is interested than services. • Features: • Mobility and roaming (service access) • Seamless roaming (service delivery) • Modular arch. • AAA and user discrimination (user-u / u-group / g-g) • Custom service development • Universal unique framework • Integrated QoS and Security

9. Service Models for Enterprise IMS • IMS architecture was designed with a focus on individual subscribers, so how can IMS services be provided to enterprises ? • Standalone IMS-Based Commun. Syst. • Fully Hosted IMS-Based Commun. Syst. • Enterprise-Based IMS-Based Commun. Syst. • Mobile Virtual Network Commun. Syst.

10. Standalone IMS-Based Commun. Syst. Architecture • HSS, AP, CSCF and MRF are located in Enterprise home. • AS • Call forwarding • Follow me • Voice mail • Routes public URI to interactive voice response (IVR) • Forward public URI to users

11. Standalone IMS-Based Commun. Syst. (cont.) Integration with the public IMS • Enterprise is one or many IMS subscribers. • Can be called from outside of enterprise domain. • By using IMS public URI • company@enterprise.com • +123456789 • Can be called from Internet • By using domain name • company@enterprise.com

12. Standalone IMS-Based Commun. Syst. (cont.) User Issue • AAA by ISIM on UICC • Teleworker and nomadic user • SIP Registration by soft-phone from their location to CSCF using their enterprise authentication information. • Mobile User • SIP Registration by soft-phone from data network in WiMAX, Wi-Fi and 3GPP.

13. Standalone IMS-Based Commun. Syst. (cont.) Benefits and Drawbacks • Small-scale IMS implementation • More modular than current enterprise VoIP system. • Mobility and roaming features of the public IMS are not used. A user needs to connect to two different system. (Public IMS / Enterprise IMS) • Users need to register to enterprise HSS again when they handoff between different access network.

14. Fully Hosted IMS-Based Commun. Syst. • The enterprise communication system completely resides within the public IMS network, in a centrex-like model. (centrex-IMS) • The centrex-IMS service provider offer a special subscription service for enterprises.

15. Fully Hosted IMS-Based Commun. Syst. (cont.) Integration with the public IMS • All enterprise user are public IMS subscribers. • Each user has one or more IMS public user identites • user@company.operator.com • subscriber@operator.com • The enterprise users can reach each other using extensions. • 206@company.operator.com • The service provider must map the enterprise private numbers to IMS public numbers by AP

16. Fully Hosted IMS-Based Commun. Syst. (cont.) User Issue • Mobility can be fully provided. Service Issue • Special filtering functions are required • allow internal calls but block external ones • allow short addressing or aliases

17. Fully Hosted IMS-Based Commun. Syst. (cont.) Benefits and Drawbacks • Suitable for small enterprises with highly mobile workforces. • User information and database may have to be duplicated or remote accessed in the public IMS. • Specific interfaces between to the operator network and the enterprise network must be provide. • No standard is available to support this.

18. Enterprise-Based IMS-Based Commun. Syst. • An intermediate solution of previous two extremes. • IMS service provider • Signaling (CSCF/HSS) • Media function (MRF) • Enterprise • AS • SIP AS • OSA AS

19. Enterprise-Based IMS-Based Commun. Syst. (cont.) Integration with the public IMS • Enterprise user are regular IMS public subscribers. • Incoming and outgoing calls must pass through the enterprise AS. • S-CSCF refers SIP message to a sequence AS (based on HSS profile), the servicer provider can refer the enterprise calls to the enterprise AS. [S3 can be implemented in this model in enterprise IMS ]

20. Enterprise-Based IMS-Based Commun. Syst. (cont.) User Issue • Mobility can be fully provided. • AAA by IMS way. Service Issue • All enterprise users are served by the enterprise AS. • Enterprise can use different services by different ASs. • Ex: S3 server.

21. Enterprise-Based IMS-Based Commun. Syst. (cont.) Benefits and Drawbacks • For IMS service provider • Avoid any special processing for enterprise user. • Enterprise users are IMS subscribers with specific HSS profiles pointing to a particular AS. • For enterprise view • Better control of company communication. • The enterprise can change, upgrade and add services without requiring the agreement of the service provider. • Certification of enterprise services are required. • Performance and security

22. Enterprise-Based IMS-Based Commun. Syst. (cont.) Benefits and Drawbacks (cont.) • OSA approach offers more protection • Not access HSS in IMS. • Some call will go from the enterprise users out into the operator network, back into enterprise network. • Delay and bandwidth consumption. [Does S3 have this problem ?]

23. Mobile Virtual Network Commun. Syst. • MVNO • Mobile op that does not own a wireless network infrastructure • Resells wireless services using the network of another mobile phone network. • A large multi-national enterprise • Does not own a wireless infrastructure • Manage their users completely • Offer the same communication for all the users independent of their geographic locations.

24. Mobile Virtual Network Commun. Syst. (cont.) • Using centrx-IMS model • The enterprise manages its own IMS infrastructure and relies on the mobile op. for management of the mobility and roaming complexities.

25. Mobile Virtual Network Commun. Syst. (cont.) • Enterprise • HSS • CSCF (S/P/I) • Mobile service providers • I-CSCF • Handoff registration of mobile users (including roamers). • SLF • Location • Corresponding HSS Detection

26. Mobile Virtual Network Commun. Syst. (cont.) User Issue • Mobility can be fully provided. • AAA by IMS way. • Enterprise must • issue its own SIM cards • establish roaming agreements

27. Mobile Virtual Network Commun. Syst. (cont.) Benefits and Drawbacks • Enterprise can • Maintain an application environment independent from mobile service provider. • Enable the delivery of a consistent user experience • Have customized arch. And services that answer their requirements.

28. IT Integration • Basic form • End users access voice and messaging services using the same application • Web portal • Advanced form • IVR system can interact with a personal information manager (PIM) to control users’ call flow • Divert calls to voice mail when end users are unavailable.

29. IT Integration (cont.) • Business application integration • Customer relationship management (CRM) • User are identified by their calling number. • Calls are forwarded to the corresponding agent • Enterprise resource planning (ERP) • Call data records may be required for back-office operations

30. IT Integration (cont.) • SOA is becoming the standard way of integrating enterprise applications • Applications are composed of loosely coupled services by using standard-based interface • Services • Can be invoked remotely • Well-defined interfaces • Self-contained

31. IT Integration (cont.) • Standard for SOA (Parlay X Web service) • Web Service Description Language (WSDL) • Describe the interface of Web service in XML • Universal description, Discovery and Integration (UDDI) • Service directory/registry [message box in YAN ?] • Business process execution language (BPEL) • Model business and orchestrate services in XML • SOAP

32. IT Integration (cont.) • IMS AS takes charge of the integration task • Coordination between IT system and AS by Web services and SOAP. • AS invokes the functionality of enterprise services (CRM/PIM) by calling Web service.

33. Experiments • Enterprise IMS-based VoIP • Stand-alone architecture • SOA approach for system integration • I-CSCF, P-CSCF and S-CSCF are co-located in a SIP AS • Result • SOA architecture was not very positive. • Implementation problem.

34. Conclusion • This paper • Discussed the requirement of enterprise commun. syst. • Presented four approaches for the use of IMS by enterprises. • Discussed the integration of enterprise commun. syst. within the enterprise IT infrastructure. • Proposed the use of service oriented architecture (SOA) to integrate enterprise IT and enterprise IMS.