Computers are becoming smaller and more mobile, as they do they are becoming relied upon more and more for critical applications. These applications require an always on high bandwidth connection from the field to the internet. It is this reason that techniques must be developed. In a system where a mobile router chooses amongst several differing types of networks, the router must be given as much information as possible so that it can make the best choice as to who it should connect to when it leaves its home network. This paper proposes that the mobile router be given a metric, called dynamic preference level, based upon the conditions of each possible next hop so that when the router needs to handoff from one access point to another it makes the best, informed, decision it can. This metric will use the amount of free bandwidth available in addition to other factors such as path loss.

With a rapid growth in wireless technology in recent years, Mobile IP has become very important for consumers and businesses by providing mobility based on IP addresses using several applications, which keep the employees connected with each others with critical information. In mobile IP the node can change its location by maintaining the same IP address and keep connected to the internet, which solves the issue of terminating the communication once it moves. Since Mobile IP uses open airwaves as a transmission medium, it is subject to the many security threats that are routed in mobile IP network .Protecting mobile IP from threats and attacks is one of the most challenging task now days. IPSec is a standard security protocol solution for TCP/IP network that provides security through Authentication, Encryption and data integrity services. Mobile IP data traffic can be secured by combining with IP Security (IPSec) protocol. This thesis describes Mobile IP operations, security threats, different existing methods for securing mobile IP and then IPSec standard, how it works and why IPSec is the best solution. This thesis also describes how to combine IPSec with a mobile IP to provide a solution called (SecMIP) that protects the mobile device’s communication from any threats. Finally it describes Mobile IPv6, binding update and associated security concern.

<p>The past few years have seen great increases in the use of portable devices like laptops, palmtops, etc. This has also led to the dramatic increase demand on wireless local area networks (WLAN) due to the flexibility and ease of use that it offers. Mobile IP and handover are important issues to be considered as these devices move within and between different networks and still have to maintain connectivity. It is, therefore, imperative to ensure seamless mobile IP handover for these devices as they move about.</p><p>In this thesis we undertake a survey to describe the real processes involved in mobile IP handover in WLAN environment for different scenarios. Our work also identifies individual sources of delay during the handoff process, the sum total of which makes up the total latency. Other factors that could militate against the aim of having a seamless handoff in an inter-subnet network roaming were also considered as well as some proposed solutions. These factors are security, packet loss and triangle routing.</p>

The past few years have seen great increases in the use of portable devices like laptops, palmtops, etc. This has also led to the dramatic increase demand on wireless local area networks (WLAN) due to the flexibility and ease of use that it offers. Mobile IP and handover are important issues to be considered as these devices move within and between different networks and still have to maintain connectivity. It is, therefore, imperative to ensure seamless mobile IP handover for these devices as they move about. In this thesis we undertake a survey to describe the real processes involved in mobile IP handover in WLAN environment for different scenarios. Our work also identifies individual sources of delay during the handoff process, the sum total of which makes up the total latency. Other factors that could militate against the aim of having a seamless handoff in an inter-subnet network roaming were also considered as well as some proposed solutions. These factors are security, packet loss and triangle routing.

In mobile IP, a triangular routing problem usually leads to additional delays and non-seamless handoff, which causes the loss of a large amount of in-fly packets. In this thesis we propose an adaptive route optimization scheme that considers the seamless handoff and mobility rate. The proposed scheme adopts the mobile routing table scheme and includes an efficient cost function. The cost function is a trade-off between network bandwidth utilized by the routing path, signaling messages and processing loads of agents. The primary idea is to adaptively determine when to perform route optimization. The effect of the mobility rate and the cell sojourn time of a mobile node are studied. Both new call and handoff call are considered in the cost calculation. Simulation result shows that the proposed scheme can effectively reduce the total cost composed of link and signaling costs.

With the flourishing development of the Internet and progress of science and technology, the wireless network technology is growing up rapidly at present. People can make connections through the Internet whenever and wherever possible. Mobile IPv6 is proposed in order to support mobility in IPv6 network, offers safer and more efficient mobile communication service to users than Mobile IPv4. However, it still suffers long delays and high packet losses. In order to enable smooth handovers, many researches in which use buffering and forwarding methods have been proposed. Although these proposals significantly improve handover performances, they suffer from the out-of-order delivery problem. This paper proposes a scheme which integrates multicast technologies with FMIPv6 for improving the handover performance. By switching between unicast addressing mode and multicast addressing mode, and letting the access router of the new network (NAR) join the multicast group in anticipation during handover, correspondent nodes (CNs) can transmit data packets to the new and old networks of mobile nodes (MNs) directly at the same time. It not only averts the out-of-order delivery problem, but also reduces the effect of the Duplicated Address Detection (DAD) time on the service disruption time.

Wireless networks introduce a whole range of challenges to the traditional TCP/IP network, especially Virtual Private Network (VPN). Changing IP address is a difficult issue for VPNs in wireless networks because IP addresses are used as one of the identifiers of a VPN connection and the change of IP addresses will break the original connection. The current solution to this problem is to run VPN tunnels over Mobile IP (MIP). However, Mobile IP itself has significant problems in performance and security and that solution is inefficient due to double tunneling. This thesis proposes and implements a new and novel solution on simulators and real devices to solve the mobility problem in a VPN. The new solution adds mobility support to existing L2TP/IPsec (Layer 2 Tunneling Protocol/IP Security) tunnels. The new solution tunnels Layer 2 packets between VPN clients and a VPN server without using Mobile IP, without incurring tunnel-re-establishment at handoff, without losing packets during handoff, achieves better security than current mobility solutions for VPN, and supports fast handoff in IPv4 networks. Experimental results on a VMware simulation showed the handoff time for the VPN tunnel to be 0.08 seconds, much better than the current method which requires a new tunnel establishment at a cost of 1.56 seconds. Experimental results with a real network of computers showed the handoff time for the VPN tunnel to be 4.8 seconds. This delay was mainly caused by getting an IP address from DHCP servers via wireless access points (4.6 seconds). The time for VPN negotiation was only 0.2 seconds. The experimental result proves that the proposed mobility solution greatly reduces the VPN negotiation time but getting an IP address from DHCP servers is a large delay which obstructs the real world application. This problem can be solved by introducing fast DHCP or supplying an IP address from a new wireless access point with a strong signal while the current Internet connection is weak. Currently, there is little work on fast DHCP and this may open a range of new research opportunities.

The content of this thesis is to research possibilities of using SNMP for management of Mobile IP activated entities. The first two chapters deal with theoretical analysis of Mobile IP protocol, and Simple Network Management Protocol. The Mobile IP protocol analysis focuses especially on the elements Home agent and Foreign agent. In the SNMP chapter the analysis focuses mainly on ways to exchange messages. Another part of the document is devoted to a description of laboratory networks com- posed of routers Cisco 1841 and the configuration of them. Finally is described the programmed application to manager these devices in JAVA, which is included in Annex. The program periodically sends SNMP queries and finds relationships between the Home agent and the mobile nodes, and between the foreign agent and the mobile nodes. The application has a user-friendly interface that is shown on the attached flash animation. Finally, the thesis summarizes the concepts described in previous chapters and the goals to achieve.

The Transmission Control Protocol (TCP), used in the Internet, was not developed for a mobile, wireless environment. One reason why TCP might encounter problems in such an environment is rapid changes of the link characteristics. These rapid changes can occur due to handover between two subnetworks (macro handover), e.g., when a mobile node switches between different access networks. A possible and realistic handover scenario could be when a mobile node is roaming between a high bandwidth local area network (LAN) with limited coverage and a low bandwidth radio link with wide area coverage. The goals of this thesis were to set up a realistic environment for measurements of the handover performance of TCP, and to observe TCP behavior when the link characteristics suddenly change. Further objectives were to analyze the results and propose solutions for improving the performance. The mobility management in the measurement setup is handled by Mobile IP. Handovers are performed between a wireless LAN (WaveLAN) and a PPP link over a GSM circuit switched data connection. Our investigation shows that several spurious TCP timeouts occur after handover from the fast link to the slow link, triggering unnecessary retransmissions and hence resulting in TCP performance degradation. To avoid unnecessary retransmissions, we suggest a resetting of the retransmission timeout value (RTO) at the moment of handover. In the case of handover from the low bandwidth link (PPP) to the high bandwidth link (WaveLAN), our measurements show that queued packets in the link layer buffer continue to flow over the PPP link even after the handover. The high bandwidth available after the switch is thus poorly utilized before the buffer of the low bandwidth link has been emptied. The IP sending process should delay putting packets in the queue of a slow link, thus avoiding large link layer queues and enabling utilization of the high bandwidth link faster. This could be achieved by flow control between the IP layer and the link layer. After the packets have started flowing over the WaveLAN, the RTO value is unnecessarily high, which could result in extensive delays in the case of packet losses. To alleviate the problems we recommend resetting the RTO value or modifying the algorithm for calculating the RTO value to faster adapt to sudden and significant decrease of the round-trip time (RTT) in the case of handover. In both handover scenarios mentioned above we have found that a small window size is favorable to mitigate the negative effects due to the rapid changes of the link characteristics. The use of Active Queue Management to avoid large window sizes would be an interesting approach for future investigations. Another interesting approach could be to have flow control between the IP layer and the link layer to avoid a large link layer queue when the handover from [one link to another occurs.]

This thesis addresses the paucity of research on network mobility with a taxonomy and a quantitative comparison on a real test bed of existing and forthcoming network mobility solutions. Broadly, network mobility solutions can be divided into two broad categories, intra-domain and inter-domain solutions. The two are distinct enough to warrant separate solutions. Network mobility solutions can also be divided into four catogories according to their implementation, (i) Mobile IP-based solutions, (ii) Mobile IP Mobile Routing, (iii) intra-domain routing protocols, and (iv) Mobile IP Foreign Agent-based solutions. This latter division by implementation serves as a useful starting point for a discussion and study of these protocols. The qualitative and quantitive comparisons presented here yield two "winning" solutions, Mobile IP with Network Address Translation (NAT) and Mobile IP Mobile Routing, both based on Mobile IP, the draft standard for Internet mobility. The two were chosen because they are the only solutions fit for production networks, not necessarily because they are the best performing solutions. Indeed, nearly all of the other solutions are promising alternatives and some, such as mobile ad hoc network (MANET) routing protocols and the solutions based on the next generation Internet (IPv6) version of Mobile IP, are particularly so. One of the solutions uses a novel extension for Mobile IP, the Multiple Home Address extension, developed and specified in this thesis, that turns a Mobile IP mobile node into a mobile router able to support dynamically sizing mobile networks while using the existing Mobile IP infrastructure. / Master of Science