為了在移動車輛裡面保持不間斷的通訊，車載網路通訊技術近年來變成熱門的研究主題，國際網路標準組織 (Internet Engineering Task Force, IETF) 延伸了移動IPv6 (Mobile IPv6) 協定制定出移動網路 (Network Mobility, NEMO) 協定來解決車輛裡面的網路移動問題。而在異質網路中，為了讓車輛可以達到連線的不間斷性，車輛上會裝配不同的網路卡介面在一個或多個車載單元（On-Board Units， OBU）上。然而，根據IETF的分析，傳統移動網路協定使用多連接技術(multihoming)會造成多重通通道 (tunnel-in-tunnel) 問題。為了克服這個藉由雙向通道 (bi-directional tunnel) 衍生出的問題，一個應用會話初始化協議 (Session Initiation Protocol, SIP) 通訊協定並且結合獨立換手機制 (IEEE 802.21 Media Independent Handoff function, MIHF)功能的移動式網路協定在此論文中提出，此SIP為基礎的移動式網路 (SIP-NEMO) 協定可以支持多連接技術。如果當車輛透過多個介面連結網路時，利用其結合的獨立換手機制，可以協助車輛管理多個不同的網路卡在一個或多個車載單元上。一旦其中一個傳輸介面訊號變得不穩定，獨立換手機制功能可以觸發SIP-NEMO，藉由重新傳送SIP邀請訊息 (SIP INVITE)，將會話分配到其他不同的介面上。或是藉由SIP 轉送方法 (SIP REFER) ，將會話轉移到其他的車載單元上。當傳輸介面訊號消失，獨立換手機制便會利用SIP註冊 (SIP REGISTER)要求，來更新目前介面的狀態。根據實驗結果，我們所提出的多連接SIP-NEMO技術，在傳輸資料上可以達到無縫換手和路徑的最佳化。

In order to maintain uninterrupted communication of a vehicle, the IETF has extended the original Mobile IPv6 mechanism to handle the network mobility problem. Since a vehicle can carry many passengers, multihoming techniques can aggregate bandwidth to provide good enough transmission quality. A vehicle is equipped with several kinds of egress interfaces on one or multiple on-board units (OBUs) to guarantee the connection continuity on heterogeneous networks. However, according to the analysis of the IETF, the state-of-the-art Network Mobility (NEMO) basic support protocol would suffer the tunnel-in-tunnel issue while extending to support multihoming. In order to avoid the same issue due to the bi-directional tunnel, a new SIP-based network mobility (SIP-NEMO) mechanism that integrates IEEE 802.21 Media Independent Handoff Function (MIHF) to support multihoming is proposed in this paper. If a vehicle can connect to the Internet via multiple access networks, MIHF helps the proposed mechanism to manage multiple interfaces on one or multiple OBUs. When one of interfaces is unstable, MIHF triggers the multihomed SIP-NEMO to distribute sessions to other available interfaces by sending a SIP INVITE request with a URI list or to transfer sessions to other available OBUs by using SIP REFER method. Once the interface is disabled, MIHF triggers the multihomed SIP-NEMO to update its status by sending a SIP REGISTER request. From the simulation results, our proposed multihomed SIP-NEMO can achieve seamless handoff and route optimization for data transmission.

[1] “National Institute of Standards and Technology,”http://www.antd.nist.gov/seamlessandsecure.shtml.
[2] “Network Simulator 2 (NS2),” http://www.isi.edu/nsnam/ns/.
[3] “Draft IEEE Standard for Local and Metropolitan Area Networks: Media Independent Handover Services,” IEEE Draft: P802.21/D10.0, Apr. 2008.
[4] F. Cacace and L. Vollero, “Managing mobility and adaptation in upcoming 802.21 enabled devices,” in Proceedings of the 4th international workshop on Wireless mobile applications and services on WLAN hotspots. ACM New York, NY, USA, 2006, pp. 1–10.
[5] Y. Choi, B. Kim, S.-H. Kim, M. In, and S. Lee, “A Multihoming Mechanism to Support Network Mobility in Next Generation Networks,” Proceedings of Asia-Pacific Conference on Communications (APCC), pp. 1–5, Aug. 2006.
[6] V. Devarapalli, R. Wakikawa, A. Petrescu, and P. Thubert, “Network Mobility Basic Support Protocol,” IETF RFC 3963, Jan. 2005.
[7] T. Ernst, “Network Mobility (NEMO) Support Goals and Requirements,” IETF RFC 4886, July 2007.
[8] T. Ernst and J. Charbon, “Multihoming with NEMO Basic Support,” Proceedings of the 1st International Conference on Mobile Computing and Ubiquitous Computing (ICMU), Jan. 2004.
[9] T. Ernst and H. Lach, “Network Mobility Support Terminology,” IETF RFC 4885, July 2007.
[10] T. Ernst, N. Montavont, R. Wakikawa, C. Ng, and K. Kuladinithi, “Motivations and Scenarios for Using Multiple Interfaces and Global Addresses,” IETF Monami6 DRAFT: draft-ietf-monami6-multihoming-motivation-scenario-03.txt, Nov. 2008.
[11] G. Gehlen, E.Weiss, S. Lukas, C. Rokitansky, and B.Walke, “Architecture of a vehicle communication gateway for media independent handover,” Proc. of WT2006, pp. 205–209, 2006.
[12] C.-M. Huang, C.-H. Lee, and J.-R. Zheng, “A Novel SIP-Based Route Optimization for Network Mobility,” IEEE Journal on Selected Areas in Communications (JSAC), vol. 24, no. 9, pp. 1682–1691, Sep. 2006.
[13] C.-M. Huang and C.-H. Lee, “Signal Reduction and Local Route Optimization of SIPBased Network Mobility,” pp. 482–487, Jun. 2006.
[14] D. Johnson, C. Perkins, and J. Arkko, “Mobility Support in IPv6,” IETF RFC 3775, June 2004.
[15] A. Johnston, S. Donovan, R. Sparks, C. Cunningham, and K. Summers, “Session Initiation Protocol (SIP) Basic Call Flow Examples,” IETF RFC 3665, Dec. 2003.
[16] W. Kellerer, C. Bettstetter, C. Schwingenschlogl, and P. Sties, “Auto Mobile Communication in a Heterogeneous and Converged World,” IEEE Personal Communications, vol. 8, no. 6, pp. 41–47, Dec. 2001.
[17] M. Kim, H. Radha, and H. Choo, “On Multicast-Based Binding Update Scheme for NEMO Environments,” in International Conference on Computational Sciences and Its Applications (ICCSA), 2008, pp. 3–8.
[18] M. Kim, H. Radha, J.-Y. Lee, and H. Choo, “An Efficient Multicast-based Binding Update Scheme for Network Mobility,” KSII Transactions on Internet and Information Systems (TIIS), vol. 2, no. 1, pp. 23–36, 2008.
[19] R. Kuntz and J. Lorchat, “Building Fault Tolerant Networks Using a Multihomed Mobile Router: A Case Study,” Proceedings of Asian Internet Engineering Conference (AINTEC), pp. 222–234, Nov. 2006.
[20] H.-Y. Lach, C. Janneteau, and A. Petrescu, “Network Mobility in Beyond-3G Systems,”IEEE Communications Magazine, vol. 41, no. 7, pp. 52–57, Jul. 2003.
[21] G. Lampropoulos, A. Salkintzis, and N. Passas, “Media-independent handover for seamless service provision in heterogeneous networks,” Communications Magazine, IEEE, vol. 46, no. 1, pp. 64–71, 2008.
[22] N. Montavont, T. Noel, and T. Ernst, “Multihoming in nested mobile networking,” in Applications and the Internet Workshops, 2004. SAINT 2004 Workshops. 2004 International Symposium on, 2004, pp. 184–189.
[23] Q. Mussabbir, W. Yao, Z. Niu, and X. Fu, “Optimized FMIPv6 Using IEEE 802.21 MIH Services in Vehicular Networks,” IEEE Transactions on Vehicular Technology, vol. 56, no. 6, pp. 3397–3407, Nov. 2007.
[24] C. Ng, T. Ernst, E. Paik, and M. Bagnulo, “Analysis of Multihoming in Network Mobility Support,” IETF RFC 4980, Oct. 2007.
[25] C. Ng, P. Thubert, M. Watari, and F. Zhao, “Network Mobility Route Optimization Problem Statement,” IETF RFC 4888, Jul. 2007.
[26] C.-W. Ng and T. Ernst, “Multiple Access Interfaces for Mobile Nodes and Networks,”Proceedings of 12th IEEE International Conference on Networks (ICON), vol. 2, pp. 774–779, Nov. 2004.
[27] C. Ng and T. Ernst, “Multiple access interfaces for mobile nodes and networks,” in Networks, 2004.(ICON 2004). Proceedings. 12th IEEE International Conference on, vol. 2, 2004.
[28] S. Pack, X. Shen, J. Mark, and J. Pan, “Mobility Management in Mobile Hotspots with Heterogeneous Multihop Wireless Links,” IEEE Communications Magazine, vol. 45, no. 9, pp. 106–112, Sep. 2007.
[29] E. Perera, V. Sivaraman, and A. Seneviratne, “Survey on Network Mobility Support,”ACM SIGMOBILE Mobile Computing and Communications Review, vol. 8, no. 2, pp. 7–19, Apr. 2004.
[30] C. Perkins and Ed, “IP Mobility Support for IPv4,” IETF RFC 3344, Aug. 2002. [31] J. Rosenberg, H. Schulzrinne, G. Camarillo, A. Johnston, J. Peterson, R. Sparks, M. Handley, and E. Schooler, “SIP: Session Initiation Protocol,” IETF RFC 3261, Jun. 2002.
[32] K. Shima, Y. Uo, N. Ogashiwa, and S. Uda, “Operational Experiment of Seamless Handover of a Mobile Router using Multiple Care-of Address Registration,” JOURNAL OF NETWORKS, vol. 1, no. 3, p. 23, 2006.
[33] R. Sparks, “The Session Initiation Protocol (SIP) Refer Method,” IETF RFC 3515, Apr. 2003.
[34] P. Thubert, R.Wakikawa, and V. Devarapalli, “Network Mobility Home Network Models,”IETF RFC 4887, July 2007.
[35] M. Tsukada, T. Ernst, R. Wakikawa, and K. Mitsuya, “Dynamic Management of Multiple Mobile Routers,” 13th IEEE International Conference on Networks jointly held with the 7th IEEE Malaysia International Conference on Communication, vol. 2, pp. 1108–1113, Nov. 2005.
[36] R. Wakikawa, V. Devarapalli, T. Ernst, and K. Nagami, “Multiple Care-of Addresses Registration,” IETF Monami6 DRAFT: draft-ietf-monami6-multiplecoa-09.txt, Aug. 2008.
[37] E. Weiss, G. Gehlen, S. Lukas, and C. Rokitansky, “Mycarevent- vehicular communication gateway for car maintenance and remote diagnosis,” Computers and Communications, 2006. ISCC ’06. Proceedings. 11th IEEE Symposium on, pp. 318–323, June 2006.