MULTIMOB Working Group D. von Hugo Internet-Draft Deutsche Telekom Laboratories Intended status: Informational H. Asaeda Expires: December 9, 2010 Keio University B. Sarikaya Huawei USA P. Seite France Telecom - Orange June 8, 2010 Evaluation of further issues on Multicast Mobility: Potential future work for WG MultiMob Abstract The WG MultiMob aims at defining a basic mobile multicast solution leveraging on network localized mobility management, i.e. Proxy Mobile IPv6 protocol. The solution would be basically based on multicast group management, i.e. IGMP/MLD, proxying at the access gateway. If such a basic solution is essential from an operational point of view, challenges with efficient resource utilization and user perceived service quality still persist. These issues may prevent large scale deployments of mobile multicast applications. This document attempts to identify topics for near future extension of work such as modifying multimob base solution, PMIPv6 and MLD/ IGMP for optimal multicast support, and adaptation of Handover optimization. Far future items such as extending to and modifying of MIPv4/v6 and DSMIP, sender (source) mobility, consideration of multiple flows and multihoming will be dealt with in a future version. Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and 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 von Hugo, et al. Expires December 9, 2010 [Page 1] Internet-Draft Future Work for MultiMob WG June 2010 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 December 9, 2010. Copyright Notice Copyright (c) 2010 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the BSD License. von Hugo, et al. Expires December 9, 2010 [Page 2] Internet-Draft Future Work for MultiMob WG June 2010 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 7 3. IGMP/MLD Proxy Architecture . . . . . . . . . . . . . . . . . 7 4. Problem Description . . . . . . . . . . . . . . . . . . . . . 8 4.1. Modification of base PMIPv6 for optimal multicast support . . . . . . . . . . . . . . . . . . . . . . . . . 8 4.2. Modification of MLD/IGMP for optimal multicast support . . 8 4.3. Consideration of Handover Optimization . . . . . . . . . . 9 4.4. Specific PMIP deployment issues . . . . . . . . . . . . . 9 5. Requirements on Solutions . . . . . . . . . . . . . . . . . . 10 6. Security Considerations . . . . . . . . . . . . . . . . . . . 11 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11 9.1. Normative References . . . . . . . . . . . . . . . . . . . 11 9.2. Informative References . . . . . . . . . . . . . . . . . . 12 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14 von Hugo, et al. Expires December 9, 2010 [Page 3] Internet-Draft Future Work for MultiMob WG June 2010 1. Introduction Chartered work of WG MultiMob focuses on documentation of proper configuration and usage of existing (specified standard) protocols within both mobility and multicast related areas to enable and support mobility for multicast services and vice versa. The current WG document [I-D.ietf-multimob-pmipv6-base-solution] does not address specific optimizations and efficiency improvements of multicast routing for network-based mobility and thus the operation may be not resource efficient nor grant the service quality expected by the end user. The described solution resolves the problem to ensure multicast reception in PMIPv6-enabled [RFC5213] networks without appropriate multicast support. However it neither automatically minimizes multicast forwarding delay to provide seamless and fast handovers for real-time services nor minimizes packet loss and reordering that result from multicast handover management as stated in [RFC5757]. Also Route Optimization is out of scope of the basic solution - an issue for reducing amount of transport resource usage and transmission delay. Thus possible enhancements and issues for solutions beyond a basic solution need to be described to enable current PMIPv6 protocols to fully support efficient mobile multicast services. Such extensions may include protocol modifications for both mobility and multicast related protocols to achieve optimizations for resource efficient and performance increasing multimob approaches. The document includes the case of mobile multicast senders using Any Source Multicast (ASM) and Source Specific Multicast (SSM) [RFC4607]. This document focuses on discussion work on multicast protocols such as IGMP/MLD operational tuning (e.g. as proposed in [I-D.asaeda-igmp-mld-optimization]) and enhancements of IGMP/MLD protocol behaviors and messages for optimal multicast support (proposed in [I-D.asaeda-igmp-mld-mobility-extension]). An alternative approach proposes the addition of acknowledgement messages on group management ([I-D.liu-multimob-reliable-igmp-mld]) and changes the unreliable protocol concept. Furthermore a modification of PMIPv6 by introducing a dedicated multicast tunnel and support of local routing is discussed in [I-D.asaeda-multimob-pmip6-extension]. Other performance improvements have been outlined in [I-D.schmidt-multimob-fmipv6-pfmipv6-multicast] where extensions to Mobile IPv6 Fast Handovers (FMIPv6) [RFC5568], and the corresponding extension for Proxy MIPv6 operation [I-D.ietf-mipshop-pfmipv6]. von Hugo, et al. Expires December 9, 2010 [Page 4] Internet-Draft Future Work for MultiMob WG June 2010 Another type of multimob work aims directly at enhancements of the current multimob base solution [I-D.ietf-multimob-pmipv6-base-solution] towards introduction of multicast traffic replication mechanisms and a reduction of the protocol complexity in terms of time consuming tunnel set-up by definition of pre- or post-configured tunnels (as provided by e.g. [I-D.zuniga-multimob-smspmip]). Further work within this topic deals with direct routing (e.g. [I-D.sijeon-multimob-mms-pmip6]) and with dynamic or automatic tunnel configuration (see e.g. [I-D.ietf-mboned-auto-multicast]). A large field of additional investigations which are partly described in detail in [RFC5757] will be mentioned for completeness and may be subject of a later WG re-chartering. +------+ +------+ | MN | =====> | MN | +------+ +------+ | . | . +--------+ +--------+ | MAG 1 | | MAG 2 | |IGMP/MLD| |IGMP/MLD| |Proxy | |Proxy | +--------+ +--------+ | | *** *** *** *** * ** ** ** * * * * Internet Subnet * * * * ** ** ** * *** *** *** *** | | +-------+ +-------+ | LMA 1 | | LMA 2 | +-------+ +-------+ | | *** *** *** *** * ** ** ** * * * * Fixed Internet * * * * ** ** ** * *** *** *** *** | +------+ | CN | +------+ Figure 1: MultiMob Scenario for chartered PMIP6 issue von Hugo, et al. Expires December 9, 2010 [Page 5] Internet-Draft Future Work for MultiMob WG June 2010 +------+ +------+ +------+ | MN | =====> | MN | ====> | MN | +------+ +------+ +------+ | . . | . . | . . +--------+ +--------+ +--------+ +--------+ | MAG 1 | | MAG 2 | | AR 1 | | AR 2 | |IGMP/MLD| |IGMP/MLD| |IGMP/MLD| |IGMP/MLD| | Proxy | | Proxy | | Proxy | | Proxy | +--------+ +--------+ +--------+ +--------+ \ / | | *** *** *** *** *** *** *** *** * ** *** ** * * ** *** ** * * * * * * Internet Subnet 1 * * Internet Subnet 2 * * * * * * ** *** ** * * ** *** ** * *** *** *** *** *** *** *** *** | | | +-------+ +-------+ | | LMA 1 | | LMA 2 | / +-------+ +-------+ / \ | / *** *** *** *** / *** *** *** *** * ** ** ** * / * ** *** ** * * * * * * Fixed Internet * * Internet Subnet 3 * * *_____* * * ** ** ** * * ** *** ** * *** *** *** *** *** .*** *** *** | . +-------+ +-------+ | CN | ====> | CN | +-------+ +-------+ Figure 2: MultiMob scenario for extended MultiMob issues Figure 1 illustrates the key components of the foreseen basic Multimob solution. The extended multicast mobility scenario, leading to above issues, is sketched in Figure 2. In summary additional to a 'Single hop, link, flow' Proxy MIP mobility for listening MNs (scenario shown in Figure 1), future work towards a complete performance-optimized scenario of a 'Multi-hop, -homed, -flow' client mobility (i.e. including MIPv6 [RFC3775] and DSMIPv6 [RFC5555]) would cover a plurality of issues. For the near von Hugo, et al. Expires December 9, 2010 [Page 6] Internet-Draft Future Work for MultiMob WG June 2010 future we see the following issues as most important: o Extension of multimob base solution o Modification of base PMIPv6 and MLD/IGMP for optimal multicast support. o Consideration of Handover optimization. All further issues which would include extensions to and modifications of MIPv4/v6 and DSMIP using IGMP/MLD Proxy and the Foreign Agent/Access Router, consideration of sender (source) mobility, support of multiple flows on multihomed mobile nodes, multi-hop transmission, Routing optimization, and so forth will be topics for a potential next stage of future work extension. 2. Terminology The key 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 [RFC2119]. This document uses the terminology defined in [RFC3775], [RFC3376], [RFC3810], [RFC5213], [RFC5757]. 3. IGMP/MLD Proxy Architecture Multimob basic solution is based on IGMPv3/MLDv2 Proxy support at the mobile access gateway (MAG) of Proxy Mobile IPv6 as shown in Figure 1. IGMPv3/MLDv2 proxy keeps multicast state on the subscriptions of the mobile nodes and only an aggregate state is kept at the local mobility anchor (LMA). When LMA receives multicast data it can forward it to the MAG without duplication because MAG takes of the packet duplication. This leads to solving the avalanche problem. By keeping multicast state locally, IGMPv3/MLDv2 Proxy introduces mobility related problems such as possible packet loss when a mobile node does a handover to another MAG and its multicast state is not modified fast enough at the LMA. IGMPv3/MLDv2 introduces tunnel convergence problem which occurs when a given MAG serves MNs that belong to different LMAs and MNs subscribe to the same multicast group. In that case MNs receive duplicate multicast data forwarded from more than one LMA. It can be foreseen that mobile access gateways will serve both mobile and fixed terminals concurrently. The tuning of multicast-related von Hugo, et al. Expires December 9, 2010 [Page 7] Internet-Draft Future Work for MultiMob WG June 2010 protocol parameters based on the terminal characteristics is needed. Parameters only applicable to mobile users need to be distinguished from the parameters applicable to fixed users. It should be also possible to distinguish between slow and fast movement and handover frequency to form corresponding tunnels for mobile users. Based on the above observations we will state the problems next and then list the requirements on possible solutions. 4. Problem Description The general issues of multicast mobility are extensively discussed and described in [RFC5757]. To reduce the complexity of the plethora of requirements listed in [RFC5757] and also in [I-D.deng-multimob-pmip6-requirement] this document summarises some lightweight solutions for multicast mobility which allow for easy deployment within realistic scenarios and architectures. Moreover we focus on approaches building directly on basic MultiMob solution [I-D.ietf-multimob-pmipv6-base-solution] which is based on IGMP/MLD Proxy functionality at the mobile access gateway, and for which already solution proposals have been described. 4.1. Modification of base PMIPv6 for optimal multicast support Currently discussed aspects of multicast optimization for PMIPv6 include introduction of multicast tunnels and support of local routing such as described in [I-D.asaeda-multimob-pmip6-extension]. For a PMIPv6 domain the establishment of a dedicated multicast tunnel is proposed which may either be dynamically set up and released or be pre-configured in a static manner. Both mobility entities MAG and LMA may be operate as MLD proxy or multicast router. Since further functional enhancements of PMIPv6 are currently under way in NETEXT WG, both the impact of new features on Mobile Multicast as well as such a Multicast-initiated proposal for PMIPv6 modification have to be considered in a continuous exchange process between MultiMob and NETEXT WGs. 4.2. Modification of MLD/IGMP for optimal multicast support Potential approaches for enhancement of group management as specified e.g. by MLDv2 [RFC3810] include operational improvements such as proper tuning in terms of default timer value modification, specific query message introduction, and standard (query) reaction suppression, beside introducing multicast router attendance control in terms of e.g. specification of a Listener Hold message as proposed in [I-D.asaeda-multimob-igmp-mld-mobility-extensions]. von Hugo, et al. Expires December 9, 2010 [Page 8] Internet-Draft Future Work for MultiMob WG June 2010 4.3. Consideration of Handover Optimization Ideally the customer experience while using multicast services should not be affected by transmission issues whether the terminal is operated in a fixed or a mobile environment. This implies not only that the terminal should be unaware of changes at network layer connectivity (seamless communication) as is typically the case in a PMIPv6 domain, but also that any impact of connectivity changes (handover) should be minimized. In the framework of Multimob this relates to reduction of delay, packet loss, and packet reordering effort for mobile multicast by applying fast handover mechanisms, which have originally been developed for unicast traffic to multicast group management. [I-D.schmidt-multimob-fmipv6-pfmipv6-multicast] works on specification of extension of the Mobile IPv6 Fast Handovers (FMIPv6) [RFC5568] and the Fast Handovers for Proxy Mobile IPv6 (PFMIPv6) [I-D.ietf-mipshop-pfmipv6] protocols to include multicast traffic management in fast handover operations. Issues for further work are details of including multicast group messaging in context transfer, for both predictive and reactive handover mode, as well as details of corresponding message exchange protocols and message design. 4.4. Specific PMIP deployment issues Currently several proposals are under work which describe extensions of the base protocol WG draft [I-D.ietf-multimob-pmipv6-base-solution]. While MAG operation will remain that of an MLD proxy additional LMA functionalities are described in [I-D.zuniga-multimob-smspmip] which allow for replication of multicast traffic and solution of the tunnel convergence problem. The dedicated multicast LMA may either set up dedicated multicast tunnels dynamically or a-priory via pre-configuration or a delayed release. Another solution on dynamic and/or automatic tunnel configuration is proposed within multicast WG MBONED [I-D.ietf-mboned-auto-multicast]. A direct or local routing approach is described in [I-D.sijeon-multimob-mms-pmip6]. This scenario may hold for short term deployment focusing on an architecture where multicast traffic is provided via the home network. However, depending on the network topology, namely the location of the content delivery network, the LMA may not be on the optimal multicast service delivery path. This enables mobile nodes to access locally available multicast services such as local channels. Figure 3 illustrates the use-case for local routing. von Hugo, et al. Expires December 9, 2010 [Page 9] Internet-Draft Future Work for MultiMob WG June 2010 +----+ |LMA | +----+ | | *** *** *** *** * ** ** ** * * * +-------------+ * Local Routing * _____ | Content | * * | Delivery | | Network | * ** ** ** * +-------------+ *** *** *** *** || || +----+ +----+ |MAG1| |MAG2| +----+ +----+ | | | | | | MN1 MN2 MN3 Figure 3: local Multicast routing In such a case, the MAG should act as a multicast router to construct the optimal multicast delivery path. If the MAG also supports MLD proxy function issue raises up on the dual mode behaviour. In such a case, a pragmatic approach could be to leverage only on multicast routing at the MAG in the PMIP domain. Whatever is the MAG operation mode, the multicast state is locally kept at the access gateway, so unknown from the mobility anchor. In other words, the multicast service is independent from the mobility service that the mobile node is receiving from the network in the form of PMIPv6 or DSMIPv6. However, handover support is still desirable but cannot be provided by the mobility anchor (i.e. HA or LMA). In such a case mobility support for locally available multicast should be provided by extending multicast protocols of IGMP or MLD. 5. Requirements on Solutions This section tries to identify requirements from the issues discussed in previous section. von Hugo, et al. Expires December 9, 2010 [Page 10] Internet-Draft Future Work for MultiMob WG June 2010 o Seamless handover (low latency and during the handover). o Similar packet loss to unicast service. o Multiple LMAs architecture. o Agnostic mobile host re-subscription. So, MAGs must be able to retrieve multicast contexts of the mobile nodes. o Solution address IPv6, IPv4 only and dual stack nodes. o Supports sender (source) mobility. o Optimal local routing. o To be completed... 6. Security Considerations This draft introduces no additional messages. Compared to [RFC3376], [RFC3810], [RFC3775], and [RFC5213] there have no additional threats been introduced. 7. IANA Considerations Whereas this document does not explicitly introduce requests to IANA some of the proposals referenced above (such as [I-D.asaeda-multimob-pmip6-extension] and [I-D.schmidt-multimob-fmipv6-pfmipv6-multicast]) specify flags for mobility messages or options. For details please see those documents. 8. Acknowledgements The authors would thank all active members of MultiMob WG, especially (in no specific order) Gorry Fairhurst, Jouni Korhonen, Thomas Schmidt, Suresh Krishnan and Matthias Waehlisch for providing continuous support and helpful comments. 9. References 9.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3314] Wasserman, M., "Recommendations for IPv6 in Third Generation Partnership Project (3GPP) Standards", RFC 3314, September 2002. [RFC3376] Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A. Thyagarajan, "Internet Group Management Protocol, Version 3", RFC 3376, October 2002. von Hugo, et al. Expires December 9, 2010 [Page 11] Internet-Draft Future Work for MultiMob WG June 2010 [RFC3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in IPv6", RFC 3775, June 2004. [RFC3810] Vida, R. and L. Costa, "Multicast Listener Discovery Version 2 (MLDv2) for IPv6", RFC 3810, June 2004. [RFC4607] Holbrook, H. and B. Cain, "Source-Specific Multicast for IP", RFC 4607, August 2006. [RFC5213] Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K., and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008. [RFC5555] Soliman, H., "Mobile IPv6 Support for Dual Stack Hosts and Routers", RFC 5555, June 2009. 9.2. Informative References [23246] "3GPP TS 23.246 V8.2.0, Multimedia Broadcast/Multicast Service (MBMS); Architecture and functional description (Release 8).", 2008. [23401] "3GPP TS 23.401 V8.2.0, General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access (Release 8).", 2008. [23402] "3GPP TS 23.402 V8.4.1, Architecture enhancements for non- 3GPP accesses (Release 8).", 2009. [I-D.asaeda-multimob-igmp-mld-mobility-extensions] Asaeda, H. and T. Schmidt, "IGMP and MLD Hold and Release Extensions for Mobility", draft-asaeda-multimob-igmp-mld-mobility-extensions-03 (work in progress), July 2009. [I-D.asaeda-multimob-igmp-mld-optimization] Asaeda, H. and S. Venaas, "Tuning the Behavior of IGMP and MLD for Mobile Hosts and Routers", draft-asaeda-multimob-igmp-mld-optimization-02 (work in progress), March 2010. [I-D.asaeda-multimob-pmip6-extension] Asaeda, H., Seite, P., and J. Xia, "PMIPv6 Extensions for Multicast", draft-asaeda-multimob-pmip6-extension-02 (work in progress), July 2009. [I-D.deng-multimob-pmip6-requirement] Deng, H., Chen, G., Schmidt, T., Seite, P., and P. Yang, "Multicast Support Requirements for Proxy Mobile IPv6", draft-deng-multimob-pmip6-requirement-02 (work in progress), July 2009. von Hugo, et al. Expires December 9, 2010 [Page 12] Internet-Draft Future Work for MultiMob WG June 2010 [I-D.liu-multimob-reliable-igmp-mld] Liu, H. and Q. Wu, "Reliable IGMP and MLD Protocols in Wireless Environment", draft-liu-multimob-reliable-igmp-mld-00 (work in progress), March 2010. [I-D.schmidt-multimob-fmipv6-pfmipv6-multicast] Schmidt, T., Waehlisch, M., Koodli, R., and G. Fairhurst, "Multicast Listener Extensions for MIPv6 and PMIPv6 Fast Handovers", draft-schmidt-multimob-fmipv6-pfmipv6-multicast-01 (work in progress), March 2010. [I-D.sijeon-multimob-mms-pmip6] Jeon, S. and Y. Kim, "Mobile Multicasting Support in Proxy Mobile IPv6", draft-sijeon-multimob-mms-pmip6-02 (work in progress), March 2010 [I-D.zuniga-multimob-smspmip] Zuniga, J., Lu, G., and A. Rahman, "Support Multicast Services Using Proxy Mobile IPv6", draft-zuniga-multimob-smspmip-02 (work in progress), June 2010. [I-D.ietf-mboned-auto-multicast] Thaler, D., Talwar, M., Aggarwal, A., Vicisano, L., and T. Pusateri, "Automatic IP Multicast Without Explicit Tunnels (AMT)", draft-ietf-mboned-auto-multicast-10 (work in progress), March 2010 [I-D.ietf-16ng-ipv4-over-802-dot-16-ipcs] Madanapalli, S., Park, S., Chakrabarti, S., and G. Montenegro, "Transmission of IPv4 packets over IEEE 802.16's IP Convergence Sublayer", draft-ietf-16ng-ipv4-over-802-dot-16-ipcs-07 (work in progress), June 2010. [I-D.ietf-manet-smf] Macker, J. (editor), "Simplified Multicast Forwarding", draft-ietf-manet-smf-10 (work in progress), March 2010. [I-D.ietf-mipshop-pfmipv6] Yokota, H., Chowdhury, K., Koodli, R., Patil, B., and F. Xia, "Fast Handovers for Proxy Mobile IPv6", draft-ietf-mipshop-pfmipv6-14 (work in progress), May 2010 von Hugo, et al. Expires December 9, 2010 [Page 13] Internet-Draft Future Work for MultiMob WG June 2010 [I-D.ietf-multimob-pmipv6-base-solution] Schmidt, T., Waehlisch, M., and S. Krishnan, "Base Deployment for Multicast Listener Support in PMIPv6 Domains", draft-ietf-multimob-pmipv6-base-solution-02 (work in progress), May 2010. [RFC5757] Schmidt, T., Waehlisch, M., and G. Fairhurst, "Multicast Mobility in MIPv6: Problem Statement and Brief Survey", RFC 5757, June 2010. [RFC3963] Devarapalli, V., Wakikawa, R., Petrescu, A., and P. Thubert, "Network Mobility (NEMO) Basic Support Protocol", RFC 3963, January 2005. [RFC5121] Patil, B., Xia, F., Sarikaya, B., Choi, JH., and S. Madanapalli, "Transmission of IPv6 via the IPv6 Convergence Sublayer over IEEE 802.16 Networks", RFC 5121, February 2008. Authors' Addresses Dirk von Hugo Deutsche Telekom Laboratories Deutsche-Telekom-Allee 7 64295 Darmstadt, Germany Email: dirk.von-hugo@telekom.de Hitoshi Asaeda Keio University Graduate School of Media and Governance 5322 Endo Fujisawa, Kanagawa 252-8520 Japan Email: asaeda@wide.ad.jp URI: http://www.sfc.wide.ad.jp/~asaeda/ Behcet Sarikaya Huawei USA 1700 Alma Dr. Suite 500 Plano, TX 75075 Email: sarikaya@ieee.org von Hugo, et al. Expires December 9, 2010 [Page 14] Internet-Draft Future Work for MultiMob WG June 2010 Pierrick Seite France Telecom - Orange 4, rue du Clos Courtel BP 91226 Cesson-Sevigne, BZH 35512 France Email: pierrick.seite@orange-ftgroup.com von Hugo, et al. Expires December 9, 2010 [Page 15]