當行動節點 (mobile node) 在不同網段移動時，行動 IP (Mobile IP) 技術提供了行動管理機制，可以讓行動節點持續的存取資料，但行動 IP技術因為過長的換手延遲 (handover latency) 時間，因而造成較低的網路效能。換手延遲包含了階層二 (layer 2) 與階層三 (layer 3) 的延遲時間，可能會造成封包遺失與降低網路效能。在本論文中我們設計了無線行動網路階層三行動管理機制 (layer 3 mobility management for wireless mobile networks) 來降低換手延遲時間。在此管理機制中，我們使用了預先換手準備功能，其中包含了兩種方法： (1) 使用者端運用多重介面技術 (multihomed) 的預先換手準備方法 (2) 伺服端運用快速換手 (fast handover) 技術的預先換手準備方法。
在第一種方法中，我們設計了階層二驅動 (layer 2 trigger) 來輔助多重介面技術，此階層二驅動是用來監控無線連線的訊號強度，當目前無線訊號微弱時，可以自動連線到附近區域訊號較強的無線存取點 (access point)。使用多重介面技術時，行動節點可以裝備兩個無線連線介面，其中一個無線連線介面連接到目前無線連線來存取資料，而另一個無線連線介面用來選擇較合適的無線存取點來連線，使用這種方式，行動節點可在換手過程中持續接收資料，因此可以在無線行動網中無縫的漫遊。
快速換手技術利用以下方法來做預先換手準備：(1) 預先取得轉交位址 (CoA: care-of-addres) (2) 在換手前預先建立一條通道 (tunnel) 來轉送 (forwarding) 封包。因此快速換手技術比行動 IP技術有較好的網路效能，但快速換手仍有兩個問題待解決：(1) 轉送封包之通道會形成三角傳輸，而需要較長的封包傳輸時間 (2) 如果行動節點無法在目前連線斷線前做好換手準備時，換手效能將會降低。因此在伺服端換手準備方法中，我們提出兩種技術來克服以上問題： (1) 動態傳輸點 (DFP: dynamic forwarding point) 管理機制 (2) 反應式通道 (RT: reactive tunneling) 管理機制。在動態傳輸點管理機制中，利用一個合適的中繼傳輸點來轉送封包，以減少多餘的封包傳輸路徑。在反向通道管理機制中，行動節點將可以在換手前取得新的轉交位址、並且可以用較少的時間來建立通道，因此行動節點將花費較少的時間在換手準備上，其結果就有較高的機會在斷線前做好換手準備。

Mobile IP defines a mobility management for mobile nodes (MNs) to continuously access data
when they change current attachment to another. However, Mobile IP suffers from the problem
of inefficient network performance due to long handover latency. The handover latency,
which consists of layer 2 (L2) and layer 3 (L3) handover delay time, may cause packet loss
and downgrade the performance of network transmission. In the dissertation, some L3 mobility
management schemes are designed and analyzed. In order to reduce handover latency,
a handover preparation procedure is applied in the proposed L3 mobility management. Two
approaches that are adopted in the dissertation are: (1) a client-side handover preparation using
multihomed technique and (2) a network-side handover preparation using fast handover
technique.
In the client-side handover preparation using multihomed technique, a L2 assisted multihomed
control scheme is proposed. It includes the design of L2 trigger and multihomed techniques.
Based on the L2 trigger, MN can collect signal strengths of nearby Access Points (APs)
and switch to a new link automatically when the current link becomes unsuitable to connect.
Using the multihomed technique, MN can prepare for handover using 2 interfaces, in which (1)
one is connected with the original link to receive packets and (2) the other one is used to access
nearby APs and select the most suitable one as the new link, in the same time. In this way, MN
can continuously transmit and receive packets during handover.
The fast handover scheme can prepare handover using two functionalities: (1) obtaining
a new care-of-address (CoA) in advance and (2) building a tunnel for packet forwarding before
handover. Therefore, the fast handover scheme has better performance than Mobile IP scheme.
However, two problems are remained to be resolved: (1) tunnel for packet forwarding causes
triangle transmission, which results in longer packet delivery time. (2) handover performance
is downgraded if MN can not complete the handover preparation before the associated link is
broken. In the network-side handover preparation scheme using the fast handover technique,
we propose (1) a dynamic forwarding point control scheme (DFP) (2) a reactive tunneling (RT)
scheme to resolve the aforementioned problems. In the DFP scheme, a forwarding point is
selected to dispatch packets to the MN. During handover, packets sent from corresponding
node (CN) to MN will be intercepted by the forwarding point and then be forwarded to MN. In
this way, the packet transmission path are reduced. In the RT scheme, a new CoA is obtained
before handover and a tunnel is built with short delay time. As a result, MN has a better chance
to finish handover preparation than fast handover scheme.

[1] J. Abley, B. Black, and V. Gill, ”Goals for IPv6 Site-Multihoming Architectures”, RFC 3582, Aug. 2003.
[2] I. F. Akyildiz, J. Xie, and S. Mohanty, ”A survey of mobility management in nextgeneration all-IP-based wireless systems”, IEEEWireles Communications, VOL. 11, NO. 4, pp. 16-28, Aug. 2004.
[3] N. Blefari-melazzi, M. Femminella and F. Pugini, ”A Layer 3 Movement Detection Algorithm Driving Handovers in Mobile IP”, ACM Wireless Networks VOL. 11, NO. 3, pp. 223-233, 2005.
[4] C. Blondia, O. Casals, L. Cerda, N. van den Wijngaert and G. Willems, ”Performance Evaluation of Layer 3 Latency HandoffMechanisms”, ACM Mobile Networks and Application, VOL. 9, NO. 6, pp. 633-645, 2004.
[5] JinHyoeck Choi, DongYun Shin, ”Fast Router Discovery with RA”, IETF draft-jinchoimobileip-frd-00.txt, June 2002.
[6] JH. Choi, DongYun. Shin, W. Haddad ”Fast Router Discovery with L2 support”, IETF Draft-ietf-dna-frd-02.txt, August 30, 2006.
[7] S. Debashis, M. Amitava, M. I Saha, and C. Mohuya, ”Mobility Support in IP: A Survey of Related Protocols,” IEEE Network, November 2004.
[8] S. Deering and R. Hinden, ”Internet Protocol, Version 6 (IPv6)”, RFC 2460, IETF, December, 1998.
[9] G. Daley ”Effects of Fast Router Advertisement on Mobile IPv6 Handovers,” ISCC 2003.
[10] L. Dimopoulou, G. Leoleis, and I. S. Venieris, ”Fast handover support in a WLAN environment: challenges and perspectives”, IEEE network, VOL. 19, NO. 3, pp. 14-20, June 2005.
[11] N. A. Fikouras, A. J. Konsgen, and C. Gorg, ”Accelerating Mobile IP Handoffs through Link Layer Information”, Proceedings of International Multiconference on Measurement, Modelling, and Evaluation of Computer-Communication Systems (MMB’01), Aachen, Germany, Sept. 2001.
[12] W. Fritsche, F. Heissenhuber, ”Mobile IPv6: Mobility Support for Next Generation Internet”, IPv6 Forum, white paper, 2000.
[13] E. Gustafsson, A. Jonsson, and C. E. Perkins, "Mobile IPv4 regional registration”, Internet draft, IETF, draft-ietf-mobileip-reg-tunnel-09.txt, June 2004.
[14] D. Hadaller, S. Keshav, and T. Brecht, ”MV-MAX: Improving wireless infrastructure access for multi-vehicular communication”, Proceedings of the 2006 SIGCOMM workshop on Challenged networks, 2006.
[15] J. HeeYoung and K. SeokJoo, ”Fast handover support in hierarchical Mobile IPv6”, Proceedings of the 6th International Conference on Advanced Communication Technology, VOL. 2, pp. 551-554, 2004.
[16] A. Helmy, ”AMulticast-based Protocol for IPMobility Support”, Proceedings of the ACM SIGCOMM 2nd International Workshop on Networked Group Communication (NGC 2000), pp. 49-58, Palo Alto, Nov. 2000.
[17] R. Hsieh, A. Seneviratne, ”A Comparison of Mechanisms for ImprovingMobile IP Handoff Latency for End-to-End TCP”, Proceedings of the 9th Annual International Conference on Mobile Computing and Networking, pp. 29-41, September 2003.
[18] R. Hsieh, Z. G. Zhou and A. Seneviratne, ”S-MIP: A Seamless Handoff Architecture for Mobile IP”. Proceedings of IEEE INFOCOM, VOL 3, pp. 1774-1784, 2003.
[19] S. H. Hwang, et.al, ”Signaling Time Analysis for Optimal Fast Handovers for Mobile IPv6”, 2004 IEEE 60th Vehicular Technology Conference, VOL.5, pp.3275-3280, 2004.
[20] R. Koodli, Ed., ”Fast Handovers for Mobile IPv6,” RFC 4068, IETF, July, 2005.
[21] S. Krishnan, N. Montavont, E. Njedjou, S. Veerepalli, A. Yegin, Ed.,”Link-layer Event Notifications for Detecting Network Attachments”, IETF draft-ietf-dna-link-information-06, February 15, 2007.
[22] H. W. Lee, S.H. Kim, W. Ryu and C. H. Yoon, ”Performance of an efficient method for association admission control in public wireless LAN systems”, Proceeding of the 60th IEEE Vehicular Technology Conference, VOL. 7, pp. 5049- 5053, Sept. 2004.
[23] R. Li, J. Li; K. Wu, Y. Xiao, and J. Xie, ”An Enhanced Fast Handover with Low Latency for Mobile IPv6”, IEEE Transactions on Wireless Communications,VOL. 7, NO. 1, Jan. 2008.
[24] Lei LI and Shinji ABE, ”A Xcast-based Seamless Handover Scheme overWireless LAN”, IEICE Transactions on Communication, VOL. E88-B, NO. 3, pp. 965-972, March 2005.
[25] M. Liebsch, A. Singh, H. Chaskar, D. Funato, and E. Shim, ”Candidate access router discovery,” Internet Draft draft-ietf-seamoby-card-protocol-08.txt, IETF, Sept. 2004.
[26] B. Liu, P. Martins, P. Bertin, ”The operation mode selection in FMIPv6”, IEEE Symposium on Computers and Communications (ISCC), pp.742-749, 2008.
[27] K. El Malki and H. Soliman, ”Simultaneous Bindings for Mobile IPv6 Fast Handovers”, Internet Draft draft-elmalki-mobileip-bicasting-v6-06.txt, July 2005.
[28] H. V. Nguyen, S. H. Roh, J. K. Ryu and S. Park, ”A Modification for Fast Handover in Hierarchical Mobile IPv6”, Proceeding of the 9th IEEE International Conference on Advanced Communication Technology, pp. 815-818, Feb 2007.
[29] A. Mishra,M. Shin, andW. Arbaugh, ”An empirical analysis of the ieee 802.11 mac layer handoff process”, SIGCOMM Comput. Commun. Rev., vol. 33, no. 2, pp. 93-102, 2003.
[30] W. Ma, Y. Fang, ”Dynamic hierarchical mobility management strategy for mobile IP networks”, IEEE Journal on Selected Areas in Communications, VOL. 22, NO. 4, pp. 664-676, May 2004.
[31] S. Mohanty, Ian F. Akyildiz, ”Performance Analysis of Handoff Techniques Based on Mobile IP, TCP-Migrate, and SIP”, IEEE Transactions on Mobile Computing, VOL. 6,
NO. 7, JULY 2007.
[32] N. Montavont and T. Noel, ”Anticipated handover over IEEE 802.11 networks”, Proceeding of IEEE International Conference on Wireless And Mobile Computing, Networking
And Communications (WiMob’2005), 2005.
[33] N. Moore, ”Optimistic Duplicate Address Detection”, IETF RFC 4429, April 2006.
[34] T. Narten, E. Nordmark, W. Simpson, H. Soliman, ”Neighbor Discovery for IP version 6 (IPv6)”, RFC 2461, IETF, December 1998.
[35] M. Nicolas and T. Noel, ”Analysis and Evaluation of Mobile IPv6 Handovers over Wireless LAN”, ACM Mobile Networks and Applications, VOL. 8, NO. 6, pp. 643-653, 2003.
[36] B. Park, S. Lee, and H. Latchman, ”A Fast Neighbor Discovery and DAD Scheme for Fast Handover in Mobile IPv6 Networks”, Proceedings of International Conference on
Mobile Communications and Learning Technologies (ICN/ICONS/MCL), pp. 201-206, April 2006.
[37] C. Perkins, Ed. ”IP Mobility Support,”, RFC 2002, IETF, 1996.
[38] C. Perkins, IP Mobility support for IPv4. RFC 3344, IETF, August 2002.
[39] C. Perkins and D. Johnson, ”Route optimization in Mobile IP”, Internet Draft draft-ietfmobileip-optim-08.txt, IETF, Feburary 1999.
[40] C. Perkins and D. Johnson, ”Mobility Support in IPv6,” RFC 3775, IETF, 2004.
[41] P. Pongpaibool, P. Sotthivirat, S. I. Kitisin, and C. Srisathapornphat, ”Fast Duplicate Address Detection for Mobile IPv6”, Proceedings of 15th IEEE International Conference on Networks (ICON), 2007.
[42] I. Ramani and S. Savage. "SyncScan: Practical Fast Handoff for 802.11 Infrastructure Networks". Proceedings of IEEE INFOCOM, pp. 675- 684, March 2005.
[43] P. Savola and T. Chown, ”A Survey of IPv6 Site Multihoming Proposals”, Proceedings of the 8th International Conference of Telecommunications (ConTEL 2005), 2005.
[44] S. Sharma, N. N. Zhu and T. C. Chiueh, ”Low-Latency Mobile IP Handoff for Infrastructure-Mode Wireless LANs”, IEEE Journal on Selected Areas in Communications, VOL. 22, NO. 4, pp. 643-652, May 2004.
[45] M. Shin, A. Mishra, and W. Arbaugh, ”Improving the Latency of 802.11hand-offs using Neighbor Graphs,” Proceedings of the 2nd international conference on Mobile systems, applications, and services, pp. 70-83, June 2004.
[46] S. Shin, A. G. Forte, A. S. Rawat, and H. Schulzrinne, ”Reducing MAC layer handoff latency
in IEEE 802.11 wireless LANs”, Proceedings of the second international workshop on Mobility management and wireless access protocols, pp. 19-26, 2004.
[47] H. Soliman, C. Castelluccia, K. EL-Malki, and L. Bellier, ”Hierarchical MIPv6 Mobility Management (HMIPv6)”, IETF RFC 4140, August, 2005.
[48] A. Stephane, A. Mihailovic, A. H. Aghvami,”Mechanisms and hierarchical topology for fast handover in wireless IP networks”, IEEE Communications Magazine, VOL. 38, NO. 11, pp. 112-115, 2000.
[49] S. Thomson and T. Narten, ”IPv6 Stateless Address Autoconfiguration”, RFC 2462, IETF, Dec, 1998.
[50] C.-C. Tseng, Y.-C. Wong, L.-H. Yen, and K.-C. Hsu, ”Proactive DAD: A Fast Address-Acquisition Strategy for Mobile IPv6 Networks”, IEEE Internet Computing, VOL. 10,
NO. 6, Nov.-Dec 2006.
[51] D. SU, S.-J. YOO, ”Fast Handover Failure-Case Analysis in Hierarchical Mobile IPv6 Networks”, IECE Transactions on communications, VOL. E89-B, NO. 6, pp. 1892-1895, 2006.
[52] H. Velayos and G. Karlsson, ”Techniques to Reduce IEEE 802.11b MAC Layer Handover Time”, Sweden, Tech. Rep. TRITA-IMIT-LCN R 03:02, ISSN 1651-7717, ISRN
KTH/IMIT/LCN/R-03/02.SE, April 2003.
[53] I. Vivaldi, B. Ali, H. Habaebi, V. Prakash, and A. Sali,”Routing scheme for macro mobility handover in hierarchical mobile IPv6 network,” Proceeding of 4th National Conference on Telecommunication Technology, 2003, pp. 88-92.
[54] C. Vogt, ”A Comprehensive and Efficient Handoff Procedure for IPv6 Mobility Support”, Proceedings of the 2006 International Symposium onWorld ofWireless,Mobile andMultimedia Networks, pp. 212 - 218, 2006.
[55] R. Wakikawa, etc, ”Multiple Care-of Addresses Registration”, IETF draft-ietf-monami6-multiplecoa-01, Oct 2006.
[56] A. Yegin et al., ”Supporting Optimized Handover for IP Mobility Requirements for Underlying Systems”, Internet Draft draft-manyfolks-12mobilereq-02.txt, IETF, 2002.
[57] K. Yong-Sung, K. Dong-Hee, B. Kyung-Jin, and S. Young-Joo, ”Performance Comparison ofMobile IPv6 and Fast Handovers forMobile IPv6 overWireless LANs”, Proceedings of IEEE Vehicular Technology Conference (VTC 2005-Fall), pp.807-811, September 2005.
[58] http://www.isi.edu/nsnam/ns/.
[59] KAME project. http://www.kame.net/.
[60] the IETF IPv6 Multihoming Working Group. http://www.ietf.org/html.charters/multi6-charter.html.
[61] Open Source Software by the Naval Research Laboratory (NRL) PROTocol Engineering Advanced Networking (PROTEAN) Research Group - MGEN(version 4).
http://mgen.pf.itd.nrl.navy.mil/. http://www.isi.edu/nsnam.
[62] MIPL Mobile IPv6 for Linux - MIPL. http://www.mobile-ipv6.org/.