Aruna Seneviratne

Survey on network mobility support

Providing unperturbed Internet connectivity to mobile hosts has been studied in the IETF for some years now, and protocols such as Mobile IP and Mobile IPv6 have been developed. We are now witnessing the emergence of mobile networks, namely a set of hosts that move collectively as a unit, such as on ships and aircrafts. The protocols for mobility support therefore need to be extended from supporting an individual mobile device to supporting an entire mobile network. In this paper we examine the state-of-the-art in network mobility support. We first motivate the problem by considering typical network mobility scenarios and identify the characteristics that require new solutions. We then study the design requirements of the protocols that support network mobility. Thereafter, we review some of the current approaches for network mobility support, and discuss their strengths and weaknesses in addressing the design requirements. We conclude by identifying some open research issues in the realization of mobile networks.

A comparison of mechanisms for improving mobile IP handoff latency for end-to-end TCP

Handoff latency results in packet losses and severe End-to-End TCP performance degradation as TCP, perceiving these losses as congestion, causes source throttling or retransmission. In order to mitigate these effects, various Mobile IP(v6) extensions have been designed to augment the base Mobile IP with hierarchical registration management, address pre-fetching and local retransmission mechanisms. While these methods have reduced the impact of losses on TCP goodput and improved handoff latency, no comparative studies have been done regarding the relative performance amongst them. In this paper, we comprehensively evaluated the impact of layer-3 handoff latency on End-to-End TCP for various Mobile IP(v6) extensions. Five such frameworks are compared with the base Mobile IPv6 framework, namely, i) Hierarchical Mobile IPv6, ii) Hierarchical Mobile IPv6 with Fast-handover, iii) (Flat) Mobile IPv6 with Fast-handover, iv) Simultaneous Bindings, and v) Seamless handoff architecture for Mobile IP (S-MIP). We propose an evaluation model examining the effect of linear and ping-pong movement on handoff latency and TCP goodput, for all above frameworks. Our results show that S-MIP performs best under both ping-pong and linear movements during a handoff, with latency comparable to a layer-2 (access layer) handoff. All other frameworks suffer from packet losses and performance degradation of some sort. We also proposed an optimization for S-MIP which improves the performance by further eliminating the possibility of packets out of order, caused by the local packet forwarding mechanisms of S-MIP.

Performance analysis on hierarchical Mobile IPv6 with fast-handoff over end-to-end TCP

Mobile IPv4 has been considered as the de facto standard in providing Internet mobility. However, as the demand for wireless mobile devices capable of executing real-time applications increases, it is necessary to provide superior handoff latency and quality of service (QoS). Mobile IPv6 is designed to resolve these issues, and has numerous applicable optimization techniques. Two ways of reducing the handoff latency, in both IPv4 and IPv6, have been proposed in the literature. One aims to reduce the (home) network registration time while the other aims to reduce the lengthy address resolution time when in a visiting network. We present a performance analysis of the current IETF proposals, namely, the hierarchical Mobile IPv6 architecture and the fast-handoff mechanism. The former is aimed at reducing the registration time while the later in reducing the address resolution time. We show through simulation that managing the registration process in a hierarchical fashion greatly reduces the overall handoff latency. Comparatively, the fast-handoff mechanism is even more capable of reducing the handoff latency. The simple superimposition of these two frameworks produces the best overall handoff latency result. However, the overall improvement is not a simple aggregation of the individual handoff latency gains. In fact, we discovered some rather non-trivial traffic behavior when these two frameworks are combined. We identify the causes which hinder the handoff performance and hence devise a set of design guidelines to improve the handoff latency further.

Measuring and Improving the Performance of Network Mobility Management in IPv6 Networks

Measuring the performance of an implementation of a set of protocols and analyzing the results is crucial to understanding the performance and limitations of the protocols in a real network environment. Based on this information, the protocols and their interactions can be improved to enhance the performance of the whole system. To this end, we have developed a network mobility testbed and implemented the network mobility (NEMO) basic support protocol and have identified problems in the architecture which affect the handoff and routing performance. To address the identified handoff performance issues, we have proposed the use of make-before-break handoffs with two network interfaces for NEMO. We have carried out a comparison study of handoffs with NEMO and have shown that the proposed scheme provides near-optimal performance. Further, we have extended a previously proposed route optimization (RO) scheme, OptiNets. We have compared the routing and header overheads using experiments and analysis and shown that the use of the extended OptiNets scheme reduces these overheads of NEMO to a level comparable with Mobile IPv6 RO. Finally, this paper shows that the proposed handoff and RO schemes enable NEMO protocol to be used in applications sensitive to delay and packet loss

SLM, a framework for session layer mobility management

This paper describes a novel framework for managing connections to mobile hosts in the Internet. The framework, SLM, integrates the notions of quality of service management and mobility management and forms a base for overall session management. We compare SLM with the currently most widely adopted mobility management framework, Mobile IP, and show how some of Mobile IPs deficiencies are overcome. The paper further presents some initial experimental results and future research.

A QoS adaptive mobility prediction scheme for wireless networks

Mobility prediction based on an individuals movement history has been reported as an effective means to decrease the call-dropping probability and to shorten handover latency. Applying various basic prediction schemes to a realistic office environment, it is shown that mobility prediction using an individuals movement history has limitations, and the statistical randomness of the user motion can prevent accurate prediction performance. We propose a QoS adaptive mobility prediction scheme to resolve these problems. A stricter QoS compliance can be achieved through a pro-active probability update mechanism, a supplementary correlative movement history and the concept of prediction confidence ratio.

Integrated personal mobility architecture: a complete personal mobility solution

The high expectations and demand for users to access the Internet from anywhere at anytime has made user mobility an important part of the design and development of the next generation mobile communications and computing. Traditionally user mobility has been divided into two areas: Terminal Mobility and Personal Mobility. In recent years terminal mobility has focused on the movement of the terminal and developed extensions to IP protocols such as Mobile IP. In contrast, personal mobility has only received limited attention, and is somewhat lagging behind. This research has either focussed on personal mobility in communications or personalisation of operating environments. As a result, to date no framework for providing true personal mobility has emerged. In this paper, we introduce a new personal mobility framework called IPMoA (Integrated Personal Mobility Architecture), which integrates both aspects of personal mobility to provide a complete personal mobility solution, and illustrate the viability of this approach through a proof-of-concept implementation.

Cost-effective broadcast for fully decentralized peer-to-peer networks

Fully unstructured and decentralized peer-to-peer networks such as Gnutella are appealing for a variety of applications, among which file-sharing is the most prominent one. The decentralized nature of these systems provides a high degree of robustness and the ability to cope with a highly dynamic and transient network environment. However, the lack of centralized directory nodes makes the task of searching more expensive and difficult. In completely unstructured peer-to-peer networks, searching can only be realized via application-layer broadcast, where query messages are routed to every node in the network. Gnutella implements application-layer broadcast by using flooding as the underlying message routing mechanism. Flooding creates a large amount of traffic and can quickly exhaust the resources of nodes in a large network. In this paper, we explore Rumor mongering (also known as Gossip) as a more cost-effective and scalable alternative to flooding for implementing services such as searching in decentralized peer-to-peer networks. We further present a new variant of the Rumor mongering protocol, which exploits the power-law characteristics of typical peer-to-peer networks and achieves a significant further reduction in cost.

The cost of peer discovery and searching in the Gnutella peer-to-peer file sharing protocol

A lot of attention has been focused on peer-to-peer file sharing systems. Gnutella is a fully distributed peer-to-peer protocol without the need for a central entity. This increases the reliability of the system by avoiding a single point of failure as well making it more immune to legal attack. The two main features of the Gnutella protocol discovery of peers and searching for files are implemented by passing different types of messages between the nodes of the Gnutella overlay network. Due to its fully distributed nature, Gnutella relies on flooding to route most of these messages, which immediately raises the question of cost and scalability. We study these aspects of the Gnutella protocol by means of simulation also considering the influence of the topology of the Gnutella network.

A practical user mobility prediction algorithm for supporting adaptive QoS in wireless networks

A number of user mobility prediction algorithms have been reported in the literature. These may be used for resource reservation and service pre-configuration/adaptation in future wireless networks to provide QoS guarantees. However, our analysis of some of these techniques using measured cellular performance shows that these models do not accurately represent the mobility patterns of users. As a result, resource reservation schemes need to reserve excessive resources, and the pre-configuration/adaptation does not work well. To overcome this, we propose an adaptive user mobility prediction algorithm that limits the reservation and configuration procedure to a subset of cells around the user. The viability and effectiveness of the proposed scheme is then demonstrated through a simulation based on measured data.