Personal networks as distributed clients for IMS

Personal networks as distributed clients for IMS
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     ICT-MobileSummit 2008 Conference Proceedings  Paul Cunningham and Miriam Cunningham (Eds)  IIMC International Information Management Corporation, 2008  ISBN: 978-1-905824-08-3  Copyright © 2008 The authors Page 1 of 9 Personal Networks as Distributed Clients for IMS Ernö KOVACS 1 , Daniel KRAFT 1 , Antonio CIMMINO 2 ~ Sandford BESSLER  3 , Majid GHADER  4 Liljana GAVRILOVSKA 5 1  NEC Europe Ltd. NEC Laboratories Europe, Network Research Division, Kurfürsten- Anlage 36, 69115 Heidelberg, Germany, Email: {ernoe.kovacs, danie.kraft} 2  Alcatel-Lucent Italy, Strategy, Marketing & Technology Via Bosco Primo,34 84091 Battipaglia(SA) – Italy Email: 3  Forschungszentrum Telekommunikation Wien (ftw),  Donau-City 1, A-1220 Vienna, Austria, Email:   4 Centre for Communication Systems Research, University of Surrey, Guildford, United Kingdom, Email:   5  Center for TeleInfrastructure, Aalborg University,  Niels Jernes Vej 12, 9220 Aalborg Ø, Denmark, Email:   Abstract: A Personal Network (PN) connects nearby and remote devices a user owns: at home, at work in the car, on his body. It enables the user to secure and easily consume services spanning these devices. Although the PN and the IP Multimedia Subsystem (IMS) have quite complementary architectures and goals, it was the aim of this work to investigate the business and technical use cases that would allow the two systems to interoperate. We could show that, besides wide area connectivity, IMS can support PNs with basic services from its group, presence,  profile and call control enablers. The PN complements the IMS services with its ability for personalized and user-centric service delivery. This offers an interesting service proposition for mobile and FMC users Keywords: Personal Network, Personal Network Federation, IP Multimedia Subsystem, Distributed Terminal 1. Introduction Digital and networked products are rapidly expanding their market share, thus creating new  possibilities for the connected and digital-enhanced lifestyle. Up to now we have seen the evolution of increasingly powerful and feature rich devices. Smart phones have included features from music players, digital cameras, office computers, navigation system, and game machines. While this convergence on the device level will continue, we increasingly witness that these devices get connected and start performing combined services for the user. Navigation systems connect via Bluetooth to the mobile phone and provide easy access to address book, SMS, voice calls, and other features. This local connectivity will increase manifold once sensor solutions (e.g. for indoor tracking) and wireless sensor networks (e.g. for environment monitoring) are deployed. Adding to that is the desire of users to permanently connect to certain devices, e.g. at home. The MAGNET Beyond [1] project has developed the Personal Network (PN) concept [2] that allows easily and securely connecting all of these devices in a personal overlay network. MAGNET Beyond has even extended this concept to so-called PN-Federations (PN-F). PN-F allows interconnecting different PNs from different uses in a secure way. Through that the PN concept develops to a complete concept for providing communication  Copyright © 2008 The authors Page 2 of 9 and services in a safe and easy way. Despite of the autonomy the PN or PN-F users have in offering and consuming PN services, there is a need to interact with today’s network operators and service providers serving non-PN subscribers. Since the PNs have an own service platform, the external service providers could inversely benefit from the PN acting as a distributed client. In this paper we examine the interworking of the PN with the IP Multimedia Subsystem (IMS). A similar concept to that of personal networks is the  Personal Distributed Environment (PDE)  ([7], [8]) introduced by the Mobile Virtual Centre of Excellence. In PDE, a device management entity (DME) performs intelligent endpoint determination for each session of a service, based on SIP signalling. The DME contains different registries that store the capabilities of a device, its location or security credentials and via specialized protocols it is able to exchange this data with other devices in the PDE. Although the PE devices are meant to be connected via intermediate networks such as UMTS, WLAN and internet service providers, the authors do not consider deeper interaction between an IMS/NGN network and the PDE. In MOPED [9] the authors present an architecture having the goal that all the devices of a user appear in the internet as a single device. The focus is on network layer, routing and less on the service interactions. Body Sensor Network (BSN) Testbed [10] implemented and tested within IST Project e-Sense [11] is another example of interworking between a specific-purpose network and IMS. In this project, context information presenting user’s mood is provided to the IMS framework, where it can be accessed from a terminal outside the BSN. The similarity  between PN/PN-F and BSN in interaction with IMS is utilising a gateway node, which  provides inbound and/or outbound connectivity. The gateway node in both examples should support SIP stack for interaction with IMS, however the interfaces to the specific-purpose network (PN/PN-F and BSN in this case) are different. The following section explains the PN/PN-F concept and how it can evolve into a complete concept for services in the ubiquitous world. In section 2 we explain IMS and why it is interesting to utilize IMS services from a PN. In section 3 we look at the implementation of PNs as a distributed IMS client. Section 4 examines the business aspects and concludes. 2. PN Overview and Features As explained in the introduction, the world is moving away from the current Internet model in which local networks are statically connected through the Internet to other networks. Instead we see more local connectivity and ad-hoc computing to be integrated into the overall networking. Especially local connections between user-owned devices are gaining interest. However, the existing technologies of the Web in conjunction with small extensions on the devices have by far not the convenience, ease-of-use, security and functionality required for a mass market. The concept of the  Personal Network (PN) approaches these problems from a radically different angle. PNs are using the concept of overlay networks to connect all personal devices of a user in a secure and trustworthy way, across local and global networks. Once imprinted to the PN, the devices stay in contact, and can use each others' services. Within the PN, the PN middleware provides service enablers supporting automatic configuration, adaptation to changes, connectivity, and service discovery and service management. Extending the PN concept, MAGNET has introduced  Personal Network–Federation (PN- F) . Using PN-F, two or more users can define a federation among their PNs. Once a PN-F is established, selected devices in one PN can communicate with selected devices in the other PN. Furthermore, services created by the PN owner can be discovered and utilized by other users. All this occurs in a secure and trustworthy way, as the PN-F establishment and operation is governed by security policies and related policy enforcement points.  Copyright © 2008 The authors Page 3 of 9 Building on the PN-F concept, a network and service structure can be established that  better fulfils the requirements of social networking and of the small world paradigm than the wide Internet does. For example, just by coming close (e.g. in communication range), PN can establish a PN-F and automatically synchronize data. A step further is the concept of a Service Provider PN   that allows having PN acting as service providers for large numbers of users. The PN connectivity layer controls all forms of local and global connectivity through the use of a Universal Convergence Layer  . The PN Networking layer provides the needed functions so that all nodes in the PN can communicate with each other. This includes mainly security, network management, and routing features. The PN Service layer consists of service enablers and capabilities, such as the Secure Context Management Framework (SCMF)  and the  MAGNET Service Management Platform (MSMP) . The SCMF provides a framework to deploy context management related functions like access components to (wireless) sensors, storage and processing components, index management, and query  processing (query, subscribe). The MSMP provides service discovery and service control function optimized for the PN case. While the PN-F concept extends the PN to become a generally useable architecture also for service providers, there is still great interest and end-user benefits to connect PNs to existing and emerging infrastructures like the IP Multimedia Subsystem (IMS), the cornerstone of Next Generation Networks (NGN). The following section introduces the IMS and shows the benefits PN users could draw from using IMS. 3. IMS Overview The IP Multimedia Subsystem (IMS) [3] defines a SIP-based functional architecture for a managed IP-based network  . Utilizing IMS, carriers can create an open, standards-based network that delivers integrated multimedia services. While srcinally designed for third-generation mobile phones, IMS has already been extended to handle different access networks, and is continuing to be extended into an access-independent platform  for service delivery.  ETSI TISPAN (Telecoms & Internet converged Services & Protocols for  Advanced Networks)  has started standardizing fixed-line extensions to IMS. Early IMS deployment has already begun - mainly focused around the implementation of VoIP, Multimedia Messaging, PoC (Push-to-Talk over Cellular) services. While short-term success is rare, it is clear that IMS will have a major impact on fixed-mobile-wireless convergence and user profiles. The longer term benefits from IMS, seen in the wide strategic context, can turn the communication infrastructure and the PN/PN-F into a  business-ready platform capable of adding real worth across the whole of value chain. PN/PN-F, acting as a client, can integrate the benefits of IMS with user-controlled  personalisation within the PN. This combination can open opportunities to service providers to avoid the loss of revenues to third parties, and to the network operators to retain their market position and revenues. When talking about clients of the IMS, we actually talk about the basic IMS functionality as well as of the respective OMA service enablers. On advanced terminals, the IMS protocol stack and the OMA service enablers are bound together in a single system interacting with the NGN network. When a PN interacts with the IMS system, we can expect that a multitude of devices inside the PN are involved. For example, a user can easily switch from one terminal in the PN to another (e.g. from his mobile phone to his home PC). In traditional systems, this would include two different registrations in the IMS system and reveal the device change to the network operator. A PN safeguards and protects the user and its privacy by shielding internal actions from the outside world. Therefore, when a user switches between terminals in the PN, the philosophy of PN demands that the IMS system will not notice. Overall, the PN will internally work as  Copyright © 2008 The authors Page 4 of 9 a large scale distributed IMS client, in which the user is in control of the service behaviour. Towards the IMS system it will look like a single system.  Figure 1: IMS Overview and PN Network In the following, we first examine general problems for the IMS integration, then discuss several of the IMS service enablers and the problems that are encountered within the PN and when interworking with the IMS system. 3.1 General Considerations A few general considerations need to be made with respect to the IMS system. The Personal  Network of the user is protecting his privacy and gives him user-centric control on his communication services. This requires that only minimal information from within the PN is exposed to the IMS system. This leads to the following design issues: • User Identity Mapping The user identity mapping from the PN to the IMS system must be flexible and should follow the MAGNET Virtual Identity concept. The needed credentials are stored in the MAGNET user profile and are applied under full user’s control. • User Agent Proxy / Service Gateway Node (SGN)  The PN presents itself towards the IMS as single user equipment. MAGNET uses the User Agent Proxy approach and has extended it to the Service Gateway Node (SGN) concept in which not only signalling and media flows, but also application level functions are managed between the PN and IMS. • Location of the SGN  A PN is a self-organizing network without central control that always needs to adapt to changes in the connectivity. Therefore, the PN has to determine a suitable location for the SGN based on the connectivity, network and host characteristics. The MAGNET middleware provides a respective election algorithm. The following section discusses details of the implementation of Call Control, Presence, Group Management and Profile Management  Copyright © 2008 The authors Page 5 of 9 3.2 Call Control between PN and IMS To enable IMS services - such as Voice and Video over IP sessions - in a Personal  Network, an important issue is the replacement of end-user terminal with the PN acting as a wide-area distributed user equipment. The entry point to the Personal  Network is the mentioned SGN (a UE Proxy), a gateway visible from the outside world and acting as a User Equipment. The following section describes handling of outbound and inbound sessions. 3.1.1 Outbound Calls Within the PN we assume the existence of standard IMS clients that are configured to locate and use the SGN. The reason for using a proxy also for outbound traffic lies in the internal organization and security of the PN. The naming system follows a hierarchical structure, which includes the node, cluster and PN name. In case the outgoing signalling is done directly, the PN node name will be disclosed to the outside world, causing a PN security breach. Such a solution would not support essential PN features like user controlled anonymity, security, mobility and flexibility. For this reason, a name conversion needs to be performed at the SGN. The same issue is valid for addresses of internal nodes; therefore a Network Address Translation (NAT) should also be enabled on the SGN. An alternative solution for the above is to use P-CSCF on the edge of the PN, instead of using a SGN. But as mentioned  before, in this case, all personal names and addresses will be disclosed to the outside world, breaching anonymity. 3.2.2 Inbound Calls In this case a user is called from the outside world who wants to receive the call on one of his personal nodes. This node must receive the call, but should not be visible outside. In order to support the anonymity, security, mobility and flexibility criteria assumed in the  previous section, we stick to the SGN concept defined earlier. The SGN is the contact point from outside world (which can be introduce by the PN agent), but it must forward INVITE messages towards the internal actual UE node. This SGN should support: INVITEINVITE100 Trying180 Ringing180 Ringing200 OK200 OK ACK ACKSIP Call EstablishedBYEBYE200 OK200 OKSGNUEMSMP UA discovery, address resolution INRP-CSCFSDReq SMN finds the best suited UE with CA SD SDRplyDiscoverNameRqst INR Resolves the address of the UE DiscoverNameRply P-CSCF : Proxy-Call Session Control Function SGN: Service Gateway Node MSMP: MAGNET Service Management Platform INR: Intentional Name Resolver  UE: User Equipment  Figure 2: MSC for Inbound Traffic
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