INFOCOM 2003Return to Main MenuS-MIP: A Seamless Handoff Architecture for Mobile IP Robert Hsieh, Zhe Guang Zhou, Aruna Seneviratne School of Electrical Engineering and Telecommunications The University of New South Wales Sydney, 2052, Australia {roberth, zheguang}@ee.unsw.edu.au, [email protected] Abstract—As the number of Mobile IP (MIP) [2] users grow, so will the demand for delay sensitive real-time applications, such as audio streaming, that require seamless handoff, namely, a packet lossless Quality-of-Service guarantee during a handoff. Two well-known approaches in reducing the MIP handoff latency have been proposed in the literature. One aims to reduce the (home) network registration time through a hierarchical management structure, while the other tries to minimize the lengthy address resolution delay by address pre-configuration through what is known as the fast-handoff mechanism. We present a novel seamless handoff architecture, S-MIP, that builds on top of the hierarchical approach [4] and the fast-handoff mechanism [3], in conjunction with a newly developed handoff algorithm based on pure software-based movement tracking techniques [16]. Using a combination of simulation and mathematical analysis, we argue that our architecture is capable of providing packet lossless handoff with latency similar to that of L2 handoff delay when using the 802.11 access technology. More importantly, S-MIP has a signaling overhead equal to that of the well-known ‘integrated’ hierarchical MIP with fast-handoff scheme [4], within the portion of the network that uses wireless links. In relation to our S-MIP architecture, we discuss issues regarding the construction of network architecture, movement tracking, registration, address resolution, handoff algorithm and data handling. Keywords – Mobile IP, Hierarchical Mobile IPv6, Seamless Handoff, Fast-handoff (Low Latency Handoff), Software-based Mobile Device Tracking I. INTRODUCTION Mobile IP (MIP) [2] describes a global mobility solution that provides host mobility management for a diverse array of applications and devices on the Internet. In Internet (IP) environments, when a mobile node moves and attaches itself to another network, it needs to obtain a new IP address. This changing of the IP address requires all existing IP connections to the mobile node be terminated and then re-connected. This is necessary as the IP routing mechanisms rely on the topological information embedded in the IP address to deliver the data to the correct end-point. Mobile IP overcomes this by introducing a level of indirection at the network (IP) layer. This indirection is provided with the use of network agents and does not require any modification to the existing routers or end correspondent nodes. With MIP, each mobile node is identified by a static home network address from its home network, regardless of the point of attachment. While a mobile node is away from its home network, it updates a special entity, a home agent, with information about its current IP address. The home agent intercepts any packets destined to the mobile node, and tunnels them to the mobile node’s current location. Thus, it is necessary for a mobile node to register its location at the home agent. The time taken for this registration process combined with the time taken for a mobile node to configure a new network care-of address in the visiting network, amounts to the overall handoff latency. Thus the handoff latency in Mobile IP is primarily due to two procedures, namely, the address resolution and the (home) network registration. There have been numerous proposals for minimizing the handoff latency of MIP. These can be broadly classified into two groups. The first group aims to reduce the network registration time by using a hierarchical network management structure while the second group attempts to reduce the address resolution time through address pre-configuration. The former is generally referred to as hierarchical handoff and the latter as fast-handoff or low-latency handoff. IETF drafts [4] and [3] incorporate the concepts of hierarchical and fast-handoff mechanisms in the IPv6 network, based on Mobile IPv6 [1]. However, although it has been shown that the combined use of hierarchical handoff and fast-handoff improves the performance, it is nonetheless not sufficient in providing a packet lossless handoff environment at IP layer, since an approximate delay of 300 to 400 milliseconds has been observed [10]. Furthermore, this combined scheme does not address the mobile ‘ping-pong’ movement problem effectively with respect to handoff delay. This paper presents an architecture which minimizes the handoff latency, in large indoor open environments, to one that is similar to that of the L2 handoff schemes, thus virtually eliminating packet loss at the L3 IP layer. The architecture is able to achieve the above with handoff signaling overheads no greater than the well understood integrated hierarchical and fast-handoff scheme, whilst being scalable, highly available and sustains fault tolerance. S-MIP explores the intersection between mobile device tracking techniques, handoff algorithms and hierarchical Mobile IP Architecture and synthesizes together key advantages from each of those in achieving a seamless handoff architecture. The rest of the 0-7803-7753-2/03/$17.00 (C) 2003 IEEE IEEE INFOCOM 2003paper is organized as follows. Section II provides the background and the related work. Then we describe the architecture which we refer to as S-MIP in Section III. The evaluation of S-MIP is presented in Section IV and we provide some concluding remarks in Section V. II. BACKGROUND AND RELEATED WORK A. Hierarchical Mobile IPv6 Hierarchical handoff schemes separate mobility management into micro mobility and macro mobility management, otherwise known as intra-domain mobility and inter-domain mobility management respectively. The central element of these schemes is the inclusion of a special conceptual entity called Mobility Anchor Point (MAP) [4]. It is normally placed at the edges of a network, above a set of access routers, which constitute its network domain. The MAP is a router or a set of routers and maintains a binding between itself and mobile nodes currently visiting its network domain. Thus, when a mobile node (MN) attaches itself to a new network, it is required to register with the MAP serving that network domain (MAP domain). The MAP intercepts
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