IP Mobility Optimizations (Mob T. Melia Opts) RG NEC Internet-Draft J. Korhonen Expires: April 20, 2006 TeliaSonera R. Aguiar IT October 17, 2005 Network initiated handovers problem statement draft-melia-mobopts-niho-ps-00 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on April 20, 2006. Copyright Notice Copyright (C) The Internet Society (2005). Abstract The document is a first study towards network support for decision making and execution of handovers. Starting form existing technologies and considering new mobile operators trends, we draw novel potential deployment scenarios and derive a set of associated functionalities. These functional components base on assumptions Melia, et al. Expires April 20, 2006 [Page 1] Internet-Draft Network Initiated Handovers October 2005 listed in the document. Application areas for network initiated handovers are therefore illustrated specifying a set of goals and non-goals. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Overview of the problem . . . . . . . . . . . . . . . . . 4 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5 2. Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . 6 3. Scenarios and Requirements . . . . . . . . . . . . . . . . . . 8 3.1. Administrative domain wise considerations . . . . . . . . 8 3.2. Technology wise considerations . . . . . . . . . . . . . . 11 3.3. NIHO Application Areas . . . . . . . . . . . . . . . . . . 11 3.4. Network assistance with global mobility management . . . . 13 3.5. Network assistance with local mobility management . . . . 13 3.6. Inter-domain handovers . . . . . . . . . . . . . . . . . . 13 4. Framework and Functional Components . . . . . . . . . . . . . 14 5. Design considerations . . . . . . . . . . . . . . . . . . . . 14 5.1. Goals . . . . . . . . . . . . . . . . . . . . . . . . . . 14 5.2. Non-goals . . . . . . . . . . . . . . . . . . . . . . . . 15 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 7. Security Considerations . . . . . . . . . . . . . . . . . . . 15 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 15 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16 9.1. Normative References . . . . . . . . . . . . . . . . . . . 16 9.2. Informative References . . . . . . . . . . . . . . . . . . 16 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18 Intellectual Property and Copyright Statements . . . . . . . . . . 19 Melia, et al. Expires April 20, 2006 [Page 2] Internet-Draft Network Initiated Handovers October 2005 1. Introduction Standards based IP mobility enabling protocols such as Mobile IP [RFC3344] [RFC3775], HIP [I-D.ietf-hip-arch], MOBIKE [I-D.ietf- mobike-design] and SCTP with address management support [I-D.ietf- tsvwg-addip-sctp] [mSCTP] are all mobile node centric. Most handover related decision making is done in the mobile node only. Public mobile network access is gaining increased offer diversity, both in terms of the types of access technologies, in terms of the diversity of the offer (with clear separation of roles between access and service providers), and in terms of the size of that offer. This diversity has been compounded by increasing number of multi-access capable terminals equipped with IP technologies. Overall, this creates a complex environment, where the mobile terminal might not have enough information or even the possibility to make an intelligent handover decision. In fact, handover decisions and inherent target network selection is not necessarily anymore based on access availability but further depends on policies and commercial roaming arrangements on access network level, access provider level and service provider level. Furthermore, the information required for an intelligent target network selection might change periodically in such a frequency that maintaining all knowledge (and intelligence) in the mobile node might not be viable anymore. Only the network will have some of this information. However, none of the mobility protocols above referred have capabilities or procedures to significantly involve the network side entities in intelligent handover decision making. A good example of the type of information only available to the network is the situation with radio resource usage. It is expected that radio resource usage optimization will be a task of major relevance in future wireless network environments, with millions of users roaming between access routers across multiple technologies (i.e. 802.11, 802.16, e.g. [draft-cui-mobopts-hcf-wlan-00]). This function can resort to mechanisms and algorithms able to gather measurements and force terminal handovers between cells. The handover can be issued according to predefined mobility patterns, mechanisms for intelligent flow balancing, mechanisms for optimized resource re-allocation, mechanisms for user-traffic performance optimization, or mechanisms for user profiling (e.g. access rights) - all of them ultimately leading to better service to be provided to the users. For these expectations to be realized, network control capabilities are required in order to provide this ability to force specific terminals to perform handovers, either between access points or between different technologies. Going even further, handovers over administrative domains i.e. inter- Melia, et al. Expires April 20, 2006 [Page 3] Internet-Draft Network Initiated Handovers October 2005 domain handovers are not explicitly prohibited with the existing IP mobility enabling protocols but at the same time these protocols are not designed or optimized for such cases in any way. Also a general network controlled triggering mechanism for a handover from an administrative domain to another does not currently exists. An emulated behavior could somehow be achieved through selective misuse of AAA like it is done on cellular side voice oriented systems these days. This problem statement document describes various scenarios where handovers could be network initiated, even over administrative domains, presenting some ideas on architecture for this situation. This, however, will further require a new handover triggering mechanism that originates from entities located in the network side, and is acted upon by entities on the mobile node. These network side entities may also be located in other administrative domains that the mobile node is currently visiting. This document also discusses and lists a set of goals and non-goals for further work that aims at enabling network initiated and assisted handovers even over administrative domains. 1.1. Overview of the problem Current standard mobility protocols provide Internet connectivity to mobile nodes roaming from one access router to another. To reduce handover latency extensions have been proposed and are currently in the stage to be accepted as experimental RFC. In all these approaches, handover is still initiated by the mobile terminal. In this document we present a list of requirements according to which this characteristic is not adequate, and the protocols need to be extended with handover initiation by the network. There has been consensus in the last months to split local mobility from global mobility. Local mobility in the access network mainly optimizes control signaling by reducing the need to update the home/ visited network about user mobility. Local mobility can be handled independently of the global mobility. As an example, the netlmm working group charter has the task to study and specify a protocol to enable mobile devices to move across an access network by reducing to the minimum the complexity in the terminal itself. Therefore the network is requested to handle user mobility by means of appropriate scheme. In this proposal the trigger for host route update executed by the network (which is actually an handover execution) is originating in the terminal. By means of layer two mechanisms (e.g. link up or link down in IEEE 802.11) or layer three mechanisms (e.g. Neighbor discovery) the terminal is detected on the new link and the route to Melia, et al. Expires April 20, 2006 [Page 4] Internet-Draft Network Initiated Handovers October 2005 the host updated for packet delivery. Thus, the whole network involvement is simply support of routing update. The real trigger/ decision comes, once again, from the terminal. In [I-D.daniel-mip-link-characteristic] some specifications are provided to enable Mobile IPv6 and Mobile IPv4 capable nodes to exchange link information with the HA and any CN. However, to generalize the approach, the link characteristics exchange should happen during the handover process, since the Binding Update handshake conclude the handover process, when (bicasted) packets are already routed to the new Care-of Address (nCoA). For instance, specialized traffic shapers could be installed in the ARs to adapt a selected MT-CN flow to the specific underlying wireless/wire line access technology. As an example of the relevance of the proposed strategy, it is expected that predictive or stochastic algorithms could be implemented at the network side (leaving less complex logic for the MN) to perform handover decision depending on the mobile user environment. For that additional (to the link characteristics) parameters such as bit rate, quality of service parameters (e.g. in IEEE 802.11e) , radio frequency, MN's view of the access point signal level, network view of the MN's sending power and roaming related information may have to be evaluated prior to any handover decision. This kind of approach has been described, for instance, in [draft-cui-mobopts-hcf-wlan-00] where a WLAN scenario is presented and extensions to Mobile IPv6 messages are introduced to support an handover control function for handover decision. The approaches described represent only a subset on the potential scenarios for real deployment. For incorporating future technologies seamlessly it is essential that specific solutions are framed under a general solution. By adding network control to such hierarchical deployment (local and global mobility domains), mobile operators gain additional control on user mobility whilst taking into account resource allocation to guarantee reliable end to end services. In this document we identify a problem statement highlighting future network requirements, showing potential architectural ideas for achieving these results. 1.2. Terminology In this document, several words are used to signify the requirements of the specification. These words are often capitalized. The key Melia, et al. Expires April 20, 2006 [Page 5] Internet-Draft Network Initiated Handovers October 2005 words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [1]. This document frequently uses the following terms: ASP Access Service provider. A network operator that provides direct IP packet forwarding to and from the end host. MRMH Mobility and Roaming Manager, usually located at home network. The Roaming Manager part is aware of administrative relationships between the home network, various ISPs and possibly with various NAPs as well. MRMV Mobility and Roaming Manager located at visited network. MRMV is generally delegated representative of MRMH in the visited network. MSP Mobility Service provider. A service provider that provides IP mobility services. In order to obtain such service, the mobile node must be authenticated and prove authorization to obtain the service. NIHO Network initiated and assisted handover. AN Access Network composed of several access routers. Identified as well as local mobility domain. 2. Assumptions This document has some few fundamental assumptions concerning the general networking environment and network initiated handovers. The rest of the document makes use of the following assumptions: Melia, et al. Expires April 20, 2006 [Page 6] Internet-Draft Network Initiated Handovers October 2005 o Reusing existing security mechanisms -- The mobile node does not need to create a new security mechanism in order to enable network initiated and assisted handover triggering. The mobile node should reuse the existing security associations it created while establishing the initial access to the network and its mobility service provider (MSP). o All mobile nodes within the scope of this document are expected to support at least one (potentially modified) existing or future IP mobility enabling protocol. o All mobile nodes, correspondent nodes and mobility management nodes are not expected to understand or support network initiated and assisted handovers. When either peer lacks support for network initiated and assisted handover triggering and signaling the peer supporting these features must fall back to the base IP mobility protocol mechanisms. o The network initiated handover concept relies on the presence of a centralized functional entity. This entity controls the network side and implement the intelligence to select nodes and targets access routers. It is not in the scope of this document to specify the policies that will be implemented here. o To provide adequate scalable support, distributed functions are required to support the above functional entity. This gives more flexibility to the overall architecture and protocol operation. o It is envisioned the presence of multi wireless access, such as 802.11, 802.16, UMTS, forming an heterogeneous composition of macro and micro cells. The network support SHOULD leverage user mobility focusing on vertical handovers. Hence, the terminal does not need to apply filtering criteria to select a target network. (which could be an expensive operation in heterogeneous environments) o Performing network initiated handover has the main implication that the network has first to assess the terminal view of the network. Signal level evaluation is a important matter when coming down to user mobility. This is typically very well handled with terminal initiated handovers and automatic evaluation of signal level. Different methods apply to different technologies. o Neighborhood discovery relates to the above assumption when neighborhood scanning is requested from the network. It is expected these functions to be available on the terminal side. Melia, et al. Expires April 20, 2006 [Page 7] Internet-Draft Network Initiated Handovers October 2005 3. Scenarios and Requirements This section describes few usage scenarios where the network initiated and assisted handover could be justified and deployed. Also we list here initial requirements for the general network initiated and assisted handover functionality. 3.1. Administrative domain wise considerations Figure 1 and Figure 2 introduce two different possible scenarios. In the first case one single administrative scenario is described. The Mobile Operator (MO) owns both the ISPs and the NAPs. It provides as well mobility services. This is the simplest case where security restrictions are less relevant. The MO has therefore full control. Figure 2 illustrates another example architecture, where the signaling and triggering relationship between home network domain, ISP domain, NAP domain and the mobile node domain are shown. Each of previously mentioned technical domains may belong to a different administrative domain. Melia, et al. Expires April 20, 2006 [Page 8] Internet-Draft Network Initiated Handovers October 2005 .--. <-++ Mobile Operator _( `. |S Home Network ( MRMH ) |i ( ` . ) ) |n `--(___.-' |g ^ |l NIHO / triggers signaling |e / | .--. V |a _( `. |d ( ISP ) |m ( ` . ) ) |i `--(___.-' |n ^ ^ |i / NIHO \ triggers signaling |s / \ |t V V |r .--. .--. |a _( `. _( `. |t ( NAP ) ( NAP ) |i ( ` . ) ) ( ` . ) ) |v `--(___.-' `--(___.-' |e | | | ) |d V ) ) NIHO trigger & signaling |o ____ ) ) ) |m |____|_Y |a /_____/ |i |n <--+ Figure 1: An overall architecture for network initiated and assisted handover. Single Administrative domain Melia, et al. Expires April 20, 2006 [Page 9] Internet-Draft Network Initiated Handovers October 2005 .--. <-+ _( `. | Home Network ( MRMH ) | ( ` . ) ) | `--(___.-' | D ^ ^ | o NIHO / triggers \ signaling | m / \ | a .--. V V .--. | i _( `. NIHO triggers _( `. | n <--- ( ISP A ) <---------------> ( ISP B ) ---> | ( ` . ) ) signaling ( ` . ) ) | `--(___.-' `--(___.-' | 1 ^ ^ ^ ^ ^ | / NIHO \ \ triggers / \ signaling | / \ \ / \ <-+ V V \ V V | D .--. .--. \ .--. .--. | o _( `. _( `. V _( `. _( `. | m ( NAP A ) ( NAP A ) ( NAP B ) ( NAP C ) | a ( ` . ) ) ( ` . ) ) ( ` . ) ) ( ` . ) ) | i `--(___.-' `--(___.-' `--(___.-' `--(___.-' | n | 2 | ) <-+ V ) ) NIHO trigger & signaling | D ____ ) ) ) | o |____|_Y | m /_____/ | 3 <-+ Figure 2: An overall architecture for network initiated and assisted handovers over multiple administrative domains The architecture in Figure 2 has been divided into three different domains. Domain 1 represents the home network or the services provider that owns and manages user's subscription. It eventually contains Internet Service Providers (ISPs) as well. Domain 2 contains Network Access Providers (NAPs). A NAP provides access services for one or more Home Networks. Domain 3 is the mobile node and may also represent the end user. The end user does not need to have any relationship with NAPs or ISPs in order the gain access to the services accessible through the home network. Melia, et al. Expires April 20, 2006 [Page 10] Internet-Draft Network Initiated Handovers October 2005 3.2. Technology wise considerations In the previous section we provided an high level view of network relationships between the different entities involved. Figure 1 and Figure 2 describes a general network view without describing which technologies are supported and where optimizations take place. It is clear MO will have different environment deployments. In the following we give some examples on how technologies can be mapped to NAP implementing several Access Networks and creating complex overlapping of macro and micro cells scenarios. +=====================================+ = UMTS MACROCELL = = = = = = +--------------------------+ = = | 802.16 CELL | = = | | = = | 802.11 | = = | oo xx @@ | = = | o o x x @ @ | = = | o ox x@ @ | = = | o xo @x @ | = = | o ox x@ @ | = = | o o x x @ @ | = = | oo xx @@ | = = +--------------------------+ = = = +=====================================+ Figure 3: Micro and Micro cells overlapping scenario These cells can be actually owned by the same or by different NAPs. In any case, the MRMH will collect information about all these cells (as visible from the terminal) across the different domains. 3.3. NIHO Application Areas At this point in time we foresee three possible application areas that are listed and briefly described in the following section. Each application area uses the NIHO triggering and signaling as part of their tasks. Melia, et al. Expires April 20, 2006 [Page 11] Internet-Draft Network Initiated Handovers October 2005 o Application for Mobility Reasons The general idea is to handle user mobility from the network side. This particular application requires network capabilities to request measurements and evaluate technologies specific link conditions. The approach can be considered similar to what current mobile networks do. As an example, if we consider WLAN environments, the network could gather (both proactive or reactive approaches apply) terminal related information and select target access points/access routers. Previous experiences [Measurement Module for mobility management in WLAN networks] already demonstrated the feasibility of the approach. The key idea is to deploy networks able to see terminal positions upon request of measurements performed either at the edge of the network or at the terminal. Scalability considerations have to be done with respect to the overhead introduced in terms of protocol operations and traffic load in the network. o Application for Resource Optimization Reasons As mentioned before, network optimization is a delicate issue when resources are scarce, especially in the access network. Although standards able to support natively quality of services capabilities are becoming mature to be sold on the market (802.11e), networks are not yet ready to support these new technologies. A cross layer design is therefore required to convey link layer specific information to decision points located in the access network. These decision points will then execute resource optimization algorithms given the existing traffic requirements and the existing network capabilities. o Application for inter-domain handover Handovers that cause the mobile to cross administrative domain borders involve inter-domain signaling. One example of this kind of scenario is when the mobile node moves between different NAPs under the same ISP or when even the ISP changes as a result of the movement. In both of these scenarios the NIHO signaling could be used to prepare the new target domain (either ISP and/or NAP) for the arriving mobile node. Especially if the handover was initiated from the network side, the handover initiating network could help distributing all security, policies, billing and service related material cross administrative domains before the mobile node arrives. Melia, et al. Expires April 20, 2006 [Page 12] Internet-Draft Network Initiated Handovers October 2005 3.4. Network assistance with global mobility management This aspect is particularly important for inter-domain handovers. The network will provide information required for speeding the handover. This information is related with two types of data: i) operator related data, such as billing information, policies, etc..; ii) terminal related data, such as security associations. 3.5. Network assistance with local mobility management This aspect is particularly important for resource optimization and intra-domain handovers. The network will provide information to lead (or impose) the mobile terminal to associate to specific access points. 3.6. Inter-domain handovers Inter-domain handovers and inter-domain handover preparations require entities involved in the triggering and signaling to have security relationships in place between them. For example the MRMH located at the home network (service provider) must have a security relationship between all ISPs the end user can use for accessing services. Also ISPs must have security relationship between all NAPs the end user can use for accessing services. However, NAPs do no necessarily need to have any relationship with the actual service provider. And going even further the end user does not need to have any relationship between NAPs and ISPs, only with the service provider. It is service provider's duty to grant access to services via any NAP and ISP the service provider has a direct or indirect pre-setup relationship. In addition to obvious security and AAA related challenges between the service operator, ISPs and NAPs, the general when and why to trigger a handover towards the mobile node is not a trivial task. The service provider's home network needs to have rather exact and up to date knowledge of the mobile node's current topological location and surrounding network conditions before it should trigger a handover on the mobile node due same policy decision at the home network. Example of such policy decisions is when a mobile node roams (after a handover) to a target network the home network does not want the end user to use for the active service set the end user has requested. As a consequence the home network MRMH triggers a new handover suggestion towards the mobile node indicating a more feasible target network (based on the information the mobile node has previously signaled to the home network MRMH). Another home network policy decision could be distributing roaming end users in visited networks based on some distribution criteria. Such criteria could, for example, be directing voice users to ISP A network, where as data service users to ISP B network. A simpler rationale can be simply Melia, et al. Expires April 20, 2006 [Page 13] Internet-Draft Network Initiated Handovers October 2005 redirecting the user to the mobile network whose charges are lower at that time. The whole policy mechanism in the home network MRMH is a complex issue and out of scope of this document. However, the home network MRMH needs information of its end users from dedicated NAP and ISP entities. These information aggregating entities are discussed in more detail in Section 4. 4. Framework and Functional Components We can draw on the previous considerations to derive a framework view. We need the following basic components: o Policy Decision Point This could be on the MRMH or MRML depending on the case. o Policy Enforcement Point Namely the access routers o Measurements Functions Collectively distributed between the access routers and the mobile terminals. o Aggregators Components The functionalities can be located at different points in the network. Overall, the PDP will retrieve data from the Measurement blocks both in the network, and from the mobile terminal. The PDP will issue policies to the PEPs, that will impose the policies. 5. Design considerations 5.1. Goals This section lists the general goals for the network initiated and assisted handovers framework design. The network initiated and assisted handover framework solution MUST fulfil all the goals listed below: Melia, et al. Expires April 20, 2006 [Page 14] Internet-Draft Network Initiated Handovers October 2005 G1 Independent of the IP mobility management mechanism -- The network initiated and assisted handover triggering mechanism must be independent of any particular IP mobility management protocol. However, there might be mappings/implementations of the triggering mechanism to a specific IP mobility protocol such as Mobile IP. G2 Work over administrative domains e.g. in inter-domain handover cases or when a multi-homed host is attached to multiple ISPs. G3 Provide similar degree of security as existing with the current security protocols. 5.2. Non-goals This section lists issues that are considered as strictly out of scope of this problem statement and requirements document. o Designing a new security framework in order to enable network initiated and assisted handover triggering. o Initial bootstrapping problem -- The mechanism to gain the initial access to some network is out of scope of. 6. IANA Considerations This document does not define any new name spaces to be managed by IANA. This document does not either reserve any new numbers or names under any existing name space managed by IANA. 7. Security Considerations At the time of writing this document, the threats to network initiated and assisted IP handovers in general, and signaling and triggering between the mobile node and corresponding network entities are not widely understood, particularly in the inter-domain handover case when the signaling and triggering takes place across administrative domains. Part of the experimental task in preparing network initiated and assisted handovers (even across administrative domains) for eventual standards track will be to better characterize threats to network initiated and assisted handovers, inter-domain triggering and signaling, and design specific mechanisms to counter them. 8. Acknowledgments Melia, et al. Expires April 20, 2006 [Page 15] Internet-Draft Network Initiated Handovers October 2005 The authors would like to thank Rajeev Koodli for his valuable comments and suggestions. 9. References 9.1. Normative References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. 9.2. Informative References [I-D.daniel-mip-link-characteristic] Park, S., "Link Characteristics Information for Mobile IP", draft-daniel-mip-link-characteristic-02 (work in progress), June 2005. [RFC3344] Perkins, C., "IP Mobility Support for IPv4", RFC 3344, August 2002. [I-D.ietf-hip-arch] Moskowitz, R. and P. Nikander, "Host Identity Protocol Architecture", draft-ietf-hip-arch-03 (work in progress), August 2005. [I-D.ietf-mobike-design] Kivinen, T. and H. Tschofenig, "Design of the MOBIKE Protocol", draft-ietf-mobike-design-03 (work in progress), July 2005. [I-D.ietf-tsvwg-addip-sctp] Stewart, R., "Stream Control Transmission Protocol (SCTP) Dynamic Address Reconfiguration", draft-ietf-tsvwg-addip-sctp-12 (work in progress), June 2005. [mSCTP] Xing, W., Karl, H., and A. Wolisz, "M-SCTP: Design and prototypical implementation of an end-to-end mobility concept", October 2002. [RFC3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in IPv6", RFC 3775, June 2004. [draft-cui-mobopts-hcf-wlan-00] Cui, Y., "Handover Control Function Based Handover for Mobile IPv6", draft-cui-mobopts-hcf-wlan-00 (work in progress), July 2005. Melia, et al. Expires April 20, 2006 [Page 16] Internet-Draft Network Initiated Handovers October 2005 [draft-daniel-mip-link-characteristic-02] Park, S., "Link Characteristics Information for Mobile IP", draft-daniel-mip-link-characteristic-02 (work in progress), June 2005. [Measurement Module for mobility management in WLAN networks] Danda, J., Pacyna, P., Sikora, M., Loziak, K., Natkaniec, M., and A. Glowacz, "Measurement Module for mobility management in WLAN networks", Second International Workshop on Multimedia Interactive Protocols and Systems, November 2004. Melia, et al. Expires April 20, 2006 [Page 17] Internet-Draft Network Initiated Handovers October 2005 Authors' Addresses Telemaco Melia NEC Europe Network Laboratories Kufuerstenanlage 36 Heidelberg 69115 Germany Phone: +49 6221 90511 42 Email: telemaco.melia@netlab.nec.de Jouni Korhonen TeliaSonera Corporation. P.O.Box 970 FIN-00051 Sonera FINLAND Phone: +358 40 534 4455 Email: jouni.korhonen@teliasonera.com Rui L.A. Aguiar Instituto de Telecomunicacoes Universidade de Aveiro Aveiro 3810 Portugal Phone: +351 234 377900 Email: ruilaa@det.ua.pt Melia, et al. Expires April 20, 2006 [Page 18] Internet-Draft Network Initiated Handovers October 2005 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. 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Disclaimer of Validity This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Copyright Statement Copyright (C) The Internet Society (2005). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Melia, et al. Expires April 20, 2006 [Page 19]