Fast Handoff Mobile IP Protocol Using A Novel Route Optimization Technique

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1 Fast Handoff Mobile IP Protocol Using A Novel Route Optimization Technique Sajal Saha 1, Asish K Mukhopadhayay 2, and Surajjan Ghose 3 1 Narula Institute of Technology/Dept. of Computer Application, Kolkata, India sajalkrsaha@rediffmail.com 2 Dr.B.C.Roy Engg. College / Dept. of ECE, Durgapur, India akm55@gmail.com 3 Jadavpur University / Dept. of CSE, Kolkata, India sghose@cse.jdvu.ac.in Abstract Route optimization is a common technique to solve the triangular routing problem in Mobile IP. This paper evaluates various route optimization schemes available in the literature and prepares a comparative analysis of those schemes. It proposes a novel pilot agent based route optimization technique that reduces the handoff delay efficiently. The scheme has been simulated using OPNET and the results show that the proposed scheme ensures packet transfer through correspondent node in a secure manner with smooth handoff even during frequent movement of mobile node without call dropping. Index Terms Route optimization, Mobile IP, Triangular routing. I. INTRODUCTION Mobile IP protocol allows a Mobile node (MN) to move from one place to another in the Internet and still maintains communication with other nodes known as correspondent nodes (CNs). In Mobile IP packets coming from CN is received by the HA which redirects it to the MN through the FA. However, the MN can send the packets directly to the CN. Thus, overall routing path becomes triangular as shown in Fig. 1. This extended routing path is known as triangular routing problem. IETF defined route optimization (RO) [2][9][10] technique in 1996 to resolve triangular routing problem. In this technique, the CN can send the packets directly to the MN. Whenever MN is away and attached to a Foreign Agent (FA) with its care-of-address (CoA), it updates the binding cache by sending binding update request to the CN. In case of further change of FA while roaming, the old FA maintains a binding cache entry for the MN, and delivers the packets to the MN s new CoA so that packet drop can not occur. The rest of the paper is organized as follows. We compare different existing RO schemes in Section 2. We present our proposed scheme in Section 3. The simulation results are presented in Section 4. Finally we present our conclusion in Section 5. Figure 1. Triangular routing in Mobile IP. II. COMPARISON OF EXISTING RO SCHEMES Pekka Nikander et el. [1] analyzed the security issues with RO in MIPv6 using Return Routability technique. Perkins [2] introduced RO extension in MIPv6 that enables reliable handoff between FA and MN. MOTOROLA introduced route optimization for iden (Integrated Dispatch Enhanced Network) system [3] where FA keeps all the binding updates for a MN and transmit those directly through tunneling to the destination node. When a new MN comes into the foreign network, the binding update is forwarded to all the FAs so that no binding warning (BW) message is introduced to HA. Quang Gao et el [5] proposed virtual HA based route optimization scheme. The basic idea presented in this paper is based on two major assumptions, a) there is actually no need of a permanent HA throughout and b) MN tends to be highly localized during session period (The period in which all active connections starts and terminates). Thus, if the temporary address is not changed during this session period, there will be no connection disruption. Actually one of the hosts within the MN's footprint is set as its virtual HA (VHA). It retains its Virtual Home Address (VHoA) during a particular session period. According to the 2nd assumption a MH is closer to its VHA (abiding to locality concepts during session period). Thus tunneling packets by VHA to MH will lower or almost eliminate the triangle routing problem. The Basic idea of [6] is to set up a correspondent agent (CA) similar to HA & FA. The proposed solution gives the task of maintaining and updating binding caches & encapsulating messages to a single CA instead of a number of correspondent hosts in a network. Chun-Hsin Wu et el. [7] proposed bi-directional route optimization technique. This technique enables a CN and a MN to communicate with each other directly without the intervention of the HA and solves the triangular routing problem using a bi-directional tunnel. Here, a correspondent agent (CA) is also introduced to keep the transparency to the CN s and also to serve multiple CN s of its subnet. The CA maintains a Binding cache and intercepts all the packets which are sent to and from the CN s. Similarly, a FA maintains a tunneling cache to implement a bi-directional technique. In [8], a new entity called Mobile Router (MR) has been proposed. These MRs are places all the way around the network so that in between every path there is at least one MR. These MRs are also designed to have wireless links. There will be high probability that there exists one or more MR in the path between HA to CN or CN to HA. Also there is high probability that the MR in the path from HA to CN will be 207

2 same as in the path from CN to HA. Instead of the CN, these MRs will keep their binding caches updated on the basis of the messages that they catch in its transition from HA to CN or vice versa. Now every time CN sends a message to HA, if it gets encountered by any of the MR in its path that has the relevant information then it intercepts the packet and tunnels it to the MN bypassing the HA. But if in any case there is no MR encountered, then the HA receives the message and tunnels it to MN as in MIP. The binding entries in MR will have a specific life time after which it will be discarded. We have considered these salient optimization schemes and prepared a comparative analysis as summarized in Table 1. TABLE I. A COMPARISON OF EXISTING PROTOCOLS Protocol/Methodology IP version Advantage / Contribution Drawback/shortcomings Hand off Latency Return Routibility 2003[1] 6 Provide Security Against active attacks through return rout ability. RO extension 1998 [2] 6 Decrease in Handoff Latency through modified registration request message and agent advertisement message. MIP RO in iden System 1997 [3] NS2 Simulation of RO in MIP 2003 [4] Virtual HA based scheme 2000 [5] 6 MN sends the packet directly to FA bypassing the HA and reduce handoff latency. The lifetime of the state created at CN is deliberately restricted to a few minutes, this leads to worthless exchange HoT message through HA every few minutes. Security Required larger memory for FA to maintain the binding cache. 4 Enables IPv4 to support RO. Only two RO messages have been used (Binding Update & Binding Warning). 4 No need of secure distribution of mobile binding, transparency, runs on basic MIP. Agent Based RO 2001[6] 6 Mobility is completely transparent to the MN, scalable, simple, performance is better than [2]. Bidirectional RO in Mobile 4 CN and MN directly IP over wireless LAN 2002 communicate with each [7] without the intervention of the HA. Mainly client application is considered, Assuming that MNs are highly localized during session period. Single Point of Failure(CA s binding cache),accessing & updating of binding cache will be time taking. Agents need to be upgraded to support some extra functionalities like binding and tunneling cache. High RO using mobile router(mr) 2003[8] 4 Scalable, Transparent, Problem of one point failure is reduced as there is a number of copies kept in all the intermediate MR. Not cost effective as a number of MNs have to be installed, More memory is needed as two MRs may keep same informations, that will be redundant. III. PROPOSED ARCHITECTURE We propose one of the Home or Foreign agents in the network to be assigned as the Pilot Agent (PA). It will act on behalf of each individual CN to maintain binding caches, and tunneling the datagram to the MNs. In this way, the route optimization function becomes transparent to the end nodes, without requiring any modification in the CNs. In addition, a PA can manage binding caches for a number of end nodes in the same subnet. When multiple CNs in the same subnet communicates with a particular MN, a single Binding Update message is required to be sent to the PA, thereby reducing signaling traffic. The binding table consists of three fields, namely home address (HoA), care-of-address (CoA) and Time to Leave (TTL). We keep the binding table as binary search tree format to reduce the mapping time in the binding table. It will speed up the searching of CoA and reduce 208

3 the handoff latency. As a binding warning message comes from an external network, security needs to be imposed. Each MN has a unique id in the binding message which can be encoded using Huffman encoding technique to obtain a compressed data. It can then be used as a checksum and appended with the binding warning message which contains the CoA of MN. On the other hand, the HA keeps record of all its MN s id and the corresponding hash function. After receiving the binding warning message, the HA itself works out the hash function with MN s unique id and its HoA and produce the checksum. If it matches the one that is received, then the HA accepts the message otherwise rejects it. After the successful authentication of binding warning message, HA sends MN s CoA to PA. In this way we achieve highly secured RO with lower handoff latency. TABLE II. SOME IMPORTANT PARAMETERS TAKEN IN SIMULATION TTL threshold 7 Sec Binding cache lifetime 100 Sec Input buffer size 8mb Maximum buffer size 50 bytes Binding update lifetime 1800sec MN registration retry maximum 4 Registration request interval 4 Minimum retransmission timeout 10 Sec Minimum retransmission timeout 120 Sec CN data rate 1 Mbps MN,CN transmitter power Watt MN,CN packet reception power threshold 0.95 dbm Figure 2. Proposed architecture. IV. RESULTS AND DISCUSSIONS We have used OPNET modeler simulator to evaluate the performance of the proposed RO scheme with the assumption that the CN s are also within the mobile IP domain. Some important parameters considered in simulation are shown in Table 2. The basic functional modules included in simulation are MN, HA, PA and two foreign agents FR0 and FR1 as shown in Fig. 2. Initially, the MN resides at the home network and receives packets from CN through the PA. When the MN starts moving towards FR0 in the foreign network, handoff occurs at 1.16 min. MN starts receiving packets at FR0 directly from PA through tunneling and bypassing HA. At 4min, the MN moves from FR0 towards FR1 via home network and handoff occurs at 5.34 and 7.96 min respectively. At FR1, the MN starts receiving packets from PA. Finally, the MN returns to its home network. During the entire movement, the MN always receives packets through the PA. Fig. 3 shows the scenario of packet sending and receiving by the CN and MN respectively. Packet receiving at the MN is more because of excess control messages. Fig. 4 shows the load analysis of different agents. There are Figure 3. Packet transfer between Corresponding node (sender) & Mobile node (receiver). Figure 4. Load analysis of different agents. 209

4 Average delay FR0 2 Average delay FR1 1 4 Average delay Home agent 3 5 Average delay Pilot agent Figure 7. Average delay of different agents. Figure 5. Average throughput analysis of different agents. sudden dips at about 1 min, 5 min and 8 min in MN and CN lines in the graph showing packet drops during handoff. It increases after handoff points 4 and 5 simultaneously as MN reaches to FR1 as shown in Fig.5. So, throughput of the agents increases depending on the presence of MN in the corresponding network as shown in Fig.6. Fig. 7 shows the propagation delay of different agents. Fig. 8 shows the average load analysis of CN and MN. Fig. 9 and Fig. 10 show the frame transmission delay of different agent and CN, MN respectively in MAC layer. Fig. 10 shows that MN changes its point of attachment from home network and enters FR0, that s why signal strength changes abruptly. It is to be noted that signal strength is always almost above the signal strength of CN. Fig. 11 shows the average propagation delay of CN and MN. Fig. 12 shows the average load of CN and MN. Fig. 14 shows the average throughput of CN and MN. Fig. 13 and 15 shows the traffic analysis of different agents. There is traffic burst for foreign routers and HA. This burst also absorbed by the PA. This proves the stabilization and optimization of the traffic in the PA. Figure 8. Average load analysis of CN and MN. Figure 9. Media access delay of different agents. Figure 6. Throughput analysis of CN and MN. Figure 10. Media access delay of CN and MN. 210

5 Figure 11. Average delay of CN and MN. V. CONCLUSION Our analysis of different existing solutions for route optimization and their comparative study reveals that none of the solutions can provide all the potential benefits of route optimization. Some of the solutions propose secure and safe packet transfer but can not overcome high handoff latency. Some of the solutions propose low handoff latency and low signaling overhead but without enough security. On the other hand, our novel scheme effectively solves the triangular routing problem without sacrificing performance, transparency and simplicity by unifying the flow of binding updates through the pilot agent. From the simulation and analysis, it is seen that our proposed PA based scheme stabilizes and optimizes mobile IP protocol with improved handoff latency. REFERENCES Figure 12. Average load of CN and MN. Figure 13. Traffic analysis of different agents. Figure 14. Average throughput of CN and MN. [1] Nikander, P.; Arkko, J.; Aura, T.; Montenegro, G., Mobile IP version 6 (MIPv6) route optimization security design Vehicular Technology Conference, VTC 2003-Fall IEEE 58th Volume 3, Issue, 6-9 Oct Page(s): Vol.3. [2] Charles E. Perkins and David B. Johnson, Route Optimization for Mobile IP, Springer journal cluster computing, (print) (online), Issue Volume 1,Number 2, June, [3] Rajesh Pal and Piy P. Peng, Mobile IP Route Optimization in an iden System, MOTOROLA Technical Developments, March [4] Hao Chen, Ljiljana Trajković, simulation of route optimization in MobileIP, [5] Qiang Gao; Acampora, A., A virtual HA based route optimization for mobile IP, Wireless Communications and Networking Conference, WCNC IEEE Volume 2, Issue, 2000 Page(s): vol. 2 [6] Vadali, R. Jianhui Li Yiqiong Wu Guohong Cao, Agentbased route optimization for mobile IP, Vehicular Technology Conference, VTC 2001 IEEE 54th Volume: 4, page(s): vol.4 [7] Chun-hsin Wu, Ann-tzung Cheng, Shao-ting Lee, Jan-ming Ho, D. T. Lee, Bi-directional Route Optimization in Mobile IP over WirelessLAN, [8] Amit Mahajan, Ben Wild, Route Optimizations In Mobile IP, f [9] Sajal Saha et al. A comparative Study of Route Optimization Protocols in Mobile IP, p , National Conference on Computing and Communication System (CoCoSys-2009), 2 nd - 4 th January [10] Abhishek Thakur et al. A Novel Route Optimization scheme in Mobile IP, BTech final dissertation, Narula Institute of Technology, West Bengal University of Technology, June 2009 Figure 15. Average traffic analysis of different agents. 211