SIPPING Working Group S. Niccolini Internet-Draft NEC Intended status: Informational S. Salsano Expires: August 27, 2007 Univ. of Rome Tor Vergata L. Veltri Univ. of Parma February 23, 2007 Requirements for vertical handover of multimedia sessions using SIP draft-niccolini-sipping-siphandover-01 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 August 27, 2007. Copyright Notice Copyright (C) The IETF Trust (2007). Niccolini, et al. Expires August 27, 2007 [Page 1] Internet-Draft SIP-based vertical handover February 2007 Abstract This document analyses the issue of handling vertical handovers among different network technologies using SIP. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Scenario for vertical handover . . . . . . . . . . . . . . . . 4 3. Requirements for Vertical Handovers . . . . . . . . . . . . . 5 4. Taxonomy of possible approaches . . . . . . . . . . . . . . . 7 5. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 8 6. Security considerations . . . . . . . . . . . . . . . . . . . 9 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 8. Informative References . . . . . . . . . . . . . . . . . . . . 11 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 12 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13 Intellectual Property and Copyright Statements . . . . . . . . . . 14 Niccolini, et al. Expires August 27, 2007 [Page 2] Internet-Draft SIP-based vertical handover February 2007 1. Introduction Let us consider a terminal (hereafter named "Mobile Host" or MH), possibly equipped with different network interfaces (i.e. a subset of WiFi, Bluetooth, GPRS, 3G, fixed Ethernet, WiMax). Each interface will receive an IP address from the corresponding Access Network (AN). Therefore the mobile host will have a set of different IP addresses and will have to select which one to use when running multimedia sessions with correspondent terminals. While the mobile host moves, the "selected" interface may become not available due to loss of signal, or could suffer high packet loss or packet delay. Under these circumstances, the MH would like to switch to another interface (using a different IP address) keeping the running sessions active. Even with a single interface the connected access network can become not available anymore and the terminal could connect to another Access Network (in this case on the same technology), which provides a different IP address. If the switch to the new AN is fast enough, the MH could also be interested in keeping the running session active. This problem has been addressed with different approaches. One approach is based on "network level" mobility solutions like Mobile IP or MobileIPv6. Another approach is based on "application level" mobility solution. The main advantage of application level mobility solutions is that they do not require any support at the network level from the different access networks, which only needs to provide plain IP connectivity. This document details the issues and the requirements regarding an "application level" mobility solution, in particular considering the solution that exploits the SIP protocol. The aim of SIP based application level mobility is to keep active a multimedia session that has been established with SIP, while the terminal switches from one network interface to another or it changes IP address on the same interface. Niccolini, et al. Expires August 27, 2007 [Page 3] Internet-Draft SIP-based vertical handover February 2007 2. Scenario for vertical handover The figure below shows a Mobile Host that wants to communicate with a "Correspondent Host" (CH). The Mobile Host can connect to different Access Networks (AN1, AN2, AN3 are represented in the figure). The different ANs could have different wireless or wired techologies and the Mobile Host could be connected to more than one Access Network at the same time if it has more than one physical network interface. Note that the Access Networks can provide public or private addresses to the mobile host (in most typical scenarios the Access Networks are likely to provide private IP addresses). For example in the figure below AN 1 and AN 3 provide a private address (as shown by the NAT box), while AN2 provides a public address. Similarly, the Correspondent Host can have a public address (like CH 1 in the figure) or a private IP address (like CH 2 in the figure). +-------+ | AN1 |-----+ ----| | NAT | +--------+ / +-------+-----+ |Corresp.| +-------+ __________ | Host 1 | | Mobile| +-------+ / \ +--------+ | Host | | AN2 | / \ +-------+ ----| | | INTERNET | + - - - + \ / \__________/ \ +-------+ +--------+ ----| AN3 |-----+ +-----|Corresp.| | | NAT | | NAT | Host 2 | +-------+-----+ +-----+--------+ The goal of the handover mechanism is to let the MH roam among different Access Networks in a seamless way. The mobility management mechanism should consider the roaming of the MH both "off call" and during an active call. The MH should be able to dinamically choose among the available ANs the one that better suits its needs (e.g. perceived quality of media flows and cost) in a given moment. It is important to notice that this draft does not address the criteria and tools for selection of the "best" access network, it only details the issues and the requirements regarding the mobility management and handover execution mechanims. Niccolini, et al. Expires August 27, 2007 [Page 4] Internet-Draft SIP-based vertical handover February 2007 3. Requirements for Vertical Handovers In this session we discuss a set of requirements that a mobility management solution based on SIP should have. o The solution should be as fast as possible. The goal is to provide a "seamless" handover with no perception from the user point of view. If it is not possible to provide a truly seamless solution, the impairment should be minimized. o The solution should support a "forward handover" (i.e. in which all the procedure is performed on the new target Access Network). This is important if the connection on the old Access Network is suddenly broken. If possible (i.e. if the connection with the old access network does not break suddenly) the solution could exploit the communication on the old access network in order to better control the handover procedure. Soft handovers (i.e. where the two active connections can be exploited in the same moment to send the session data) could be exploited. o The handover solution should be compatible with NATted networks, i.e. it should interoperate gracefully with NAT traversal mechanisms for SIP signaling and for session media flows. o The handover solution should not require a support in the different access network. The access networks are only required to provide IP connectivity (either with public or private addresses) for the forwarding of signalling SIP packets and media RTP packets. o The switch of the "active" interface during a SIP transaction should be supported. As an example the terminal should be able to send (receive) an INVITE on the currenlty active interface, switch to another interface and receive (send) the 200 OK on the other interface. o An optional desirable requirement is to allow the decoupling of "user level" registration and mobility and "terminal level" mobility. As an example a user with AOR "sip:user@domain.com" should be allowed to use different terminals (i.e. Mobile Hosts supporting the handover solutions as well as normal SIP terminals). These terminals can be used in sequence or at the same time depending on the capability of his own "home" registrar/ proxy server, and this is independent of the vertical handover solution which takes care of the mobility of only one specific Mobile Host. A concrete example for this requirement is to support a user "sip:user@domain.com" who owns three Mobile Hosts (one could be his phone, one his PDA, one his laptop) and two Niccolini, et al. Expires August 27, 2007 [Page 5] Internet-Draft SIP-based vertical handover February 2007 fixed terminals (his desktop and his home VoIP phone). The vertical handover solution takes care of the mobility of the phone, PDA and laptop as three separate Mobile Hosts (which can also be all active in the same time). o An optional desirable requirement is to provide privacy with respect to user location and user movements. o Another desirable feature is that existing user agents should inter-work with the handover procedure without the need to be updated. This requirement applies especially to the "Correspondent Hosts" (which in general are not moving, but they are communicating with a moving terminal). If this requirement is not fulfilled there is the need to change all SIP terminals to support the handovers of Mobile Host. To a lesser extent this requirements also applies to the Mobile Host itself: it would be desirable to reuse existing SIP clients (User Agents) without updating them to support the terminal mobility. Niccolini, et al. Expires August 27, 2007 [Page 6] Internet-Draft SIP-based vertical handover February 2007 4. Taxonomy of possible approaches The application level mobility solutions based on SIP can be classified in "Correspondent host based" or "Intermediate Element based". o Correspondent Host based solutions RFC 3261 [1] has a built in mechanism for mobility management. The "off-call" mobility management consists in the Registration process. The "on-call" handover is performed using RE-INVITE messages towards the Corresponding Node. No intermediate entities are directly involved in the handover process. This has the advantage that no additional procedure for the handover needs to be implemented in network elements, and that there is no additional load in the networks due to the handovers. On the other hand, the procedure requirese that the Corresponding Node (which in general is not a mobile host) supports the RE-INVITE mechanism. A second drawback is that the handover delay is directly proportional to the end-to-end delay, and this could be higher with respect to the delay occurring between a mobile node and an intermediate entity. o Intermediate Element based solutions In order to overcome the drawbacks of the Correspondent Host based solutions, "intermediate" entities that take an active role in the handover can be introduced. Several proposals can be found in the literature, but to our knowledge no internet draft has been proposed in this respect. Hereafter we mention some of the existing proposals. In [2] intermediate entities are used only to speed up the handover process, but the handover procedure still involves the Corresponding Node as well. A similar approach is followed in [4], which also deals with location based selection of the "optimal" intermediate entity and of wireless access points. In [3] the intermediate entities fully handle the user mobility, hiding the mobility to the Corresponding Nodes. Niccolini, et al. Expires August 27, 2007 [Page 7] Internet-Draft SIP-based vertical handover February 2007 5. Conclusions As a concluding remark, we believe that it is important to consider a new solution for vertical handover that meets the set of requirements that has been analysed. This solution will help providing seamless handover to SIP based application with a better performance and overcoming some shortcomings of the current solution based on [1]. Niccolini, et al. Expires August 27, 2007 [Page 8] Internet-Draft SIP-based vertical handover February 2007 6. Security considerations The security considerations should be taken into account in the design of the handover solution, so that no new additional security issues will be introduced. Niccolini, et al. Expires August 27, 2007 [Page 9] Internet-Draft SIP-based vertical handover February 2007 7. IANA Considerations This document does not require IANA actions. Niccolini, et al. Expires August 27, 2007 [Page 10] Internet-Draft SIP-based vertical handover February 2007 8. Informative References [1] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP: Session Initiation Protocol", RFC 3261, June 2002. [2] N. Banerjee et al., "Seamless SIP-Based Mobility for Multimedia Applications", IEEE Network , March/April 2006. [3] S. Salsano et al., "Architecture and testbed implementation of vertical handovers based on SIP Session Border Controllers", to appear in Wireless Personal Communications, Springer , 2007. [4] S. Tsiakkouris, I. Wassell, "PROFITIS: architecture for location-based vertical handovers supporting real-time applications", 25th IEEE International Performance, Computing, and Communications Conference, IPCCC 2006, Phoenix, Arizona, April 10-12, 2006 . Niccolini, et al. Expires August 27, 2007 [Page 11] Internet-Draft SIP-based vertical handover February 2007 Appendix A. Acknowledgments The authors would like to thank Chiara Mingardi (Univ. of Padova/NEC) and Andrea Polidoro (Univ. of Rome Tor Vergata) for their support in the identification of the requirements and the fruitful discussions about possible solutions. Niccolini, et al. Expires August 27, 2007 [Page 12] Internet-Draft SIP-based vertical handover February 2007 Authors' Addresses Saverio Niccolini Network Laboratories, NEC Europe Ltd. Kurfuersten-Anlage 36 Heidelberg 69115 Germany Phone: +49 (0) 6221 43 42 118 Email: saverio.niccolini@netlab.nec.de URI: http://www.netlab.nec.de Stefano Salsano DIE, University of Rome "TorVergata" Via Politecnico, 1 Rome 00156 Italy Phone: +39 06 7259 7770 Email: stefano.salsano@uniroma2.it URI: http://netgroup.uniroma2.it/Stefano_Salsano Luca Veltri DII, University of Parma Parco Area delle Scienze 181/A Parma 43100 Italy Phone: +39 0521 90 5768 Email: luca.veltri@unipr.it URI: http://www.tlc.unipr.it/veltri Niccolini, et al. Expires August 27, 2007 [Page 13] Internet-Draft SIP-based vertical handover February 2007 Full Copyright Statement Copyright (C) The IETF Trust (2007). 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. 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