William Lau

Universal network of small wireless operators (UNSWo)

The recent auctioning of wireless bandwidth in various countries indicates that the service provided by Telcos over these networks will be very expensive. A new type of architecture is currently evolving as a low cost alternative cellular wireless service by allowing the users to play the role of a wireless network operator. Some users of the current Internet may install a low cost base station based on their needs and interconnection between these base stations will form a grid of wireless Internet. This paper provides a survey on related work that either uses ad-hoc mobile networking or a combination of fixed and wireless networking. Finally we present an alternate architecture and describe new issues that arise from this new type of architecture.

Failure-Oriented Path Restoration Algorithm for Survivable Networks

A new polynomial-time approximation algorithm called service path local optimization (SPLO) is presented. SPLO is shown to perform competitively with existing non-polynomial approximations based on the failure-oriented approach. SPLO is designed for online computation where only one request is computed at a time, and the decision making does not depend on future requests. The polynomial-time and online nature of the algorithm makes SPLO suitable for use in real-time on-demand path request applications. In addition, a non-polynomial approximation algorithm based on SPLO called nSPLO is proposed. Result shows that spare capacity is reduced significantly but at the cost of substantially higher computation run-time. The paper also introduces a new concept called path intermix where the service paths allocated bandwidth can be used by the backup paths protecting that particular service path. The result shows that path intermix can reduce spare capacity by up to 5% for single node failure.

Failure-oriented path restoration algorithm for survivable networks

In this article, a new polynomial-time approximation algorithm called Service Path Local Optimization (SPLO) is proposed for the online restoration problem. SPLO is shown to perform competitively with existing offline heuristics algorithm in terms of spare capacity. SPLO is designed for online computation where only one request is computed at any one time, and the decision making does not depend on future requests. The polynomial-time and online nature of the algorithm makes SPLO suitable for use in real-time on-demand path request applications. SPLO can be combined with a non-polynomial post-processing component that re-optimizes the backup paths. Significant reductions in spare capacity requirements are achievable at the expense of higher computation time. Further, the potential for SPLO as an algorithm in traffic engineering applications is investigated by looking at the performance impact when source-destination-based traffic aggregation is applied. We also introduce a new concept called path intermix where the service path¿s allocated bandwidth can be used by the backup paths protecting that particular service path.

Recent directions in virtual private network solutions

VPN services have been around for decades but it did not get wide-spread usage until recently. A combination of new VPN technologies, network technologies and business communication requirements are the driving force behind the VPN services. This survey gives an overview of the recent approaches of VPN solutions and compare their scalability and flexibility aspects. The survey also categorises VPN solutions and relates them to potential customer segments with a view to provide a better understanding of the trade-offs that a network provider faces.

Efficient bandwidth guaranteed restoration algorithms for multicast connections

This paper defines a new restoration strategy for provisioning bandwidth guaranteed recovery for multicast connections in presence of link failures. The new restoration strategy is formulated into a new Integer Linear Programming (ILP) algorithm and is compared with other existing restoration strategies. We also present a new heuristic algorithm based on this new restoration strategy. Results show that our heuristic algorithm performs competitively close to the ILP-based algorithm, and is more bandwidth efficient than other existing heuristic algorithms that are based on different restoration strategies.

An analysis of virtual private network solutions

VPN services have been available for decades but not widely used until recently. A combination of new VPN technologies, network technologies and business communication requirements is the driving force behind the take-up of VPN services. This paper gives an overview of recent VPN solutions and analyses their scalability and flexibility. VPN solutions are categorized and related to potential customer segments. Furthermore, measurements based on a large north-American carriers backbone are presented. The results show that provision of a moderate number of large VPNs puts higher constraints on the provider network than a large number of moderately sized VPNs.

Current directions in active programmable network

The active programmable network (APN) has begun a new phenomenon in the logical view towards network in the Internet domain. Traditional technologies based on IP have viewed the network as a black box where the network is hidden from the upper layers. The advantage of this model is the simplicity and the robustness it can offer. However, this model may not be appropriate for the future applications of the Internet where the integration of services are expected. The APN can be considered as an alternative model where components within the network are open for programmability.

Joint-path computation algorithms for restoration networks

This paper presents a new approach called the backup path cost estimation (BPCE) for calculating the service (working) path in the online restoration problem. The objective of BPCE is to increase bandwidth efficiency and reduce the number of blocked requests in limited capacity networks. We propose two new algorithms that combine the BPCE approach with an existing restoration algorithm called shortest path local optimization (SPLO). One of the algorithms called BPCE-SPLO aims to reduce the total bandwidth requirement of the service path and the backup paths. The second algorithm called biased-SPLO aims to reduce the backup bandwidth requirement only. Both BPCE-SPLO and biased-SPLO have polynomial-time complexity. A comparative analysis is used to evaluate the performance of BPCE-SPLO and biased-SPLO. For the comparison, we include another known polynomial-time algorithm. Results have shown that BPCE-SPLO has a slightly lower total bandwidth requirement and has a significantly lower number of blocked requests in limited capacity networks than the other algorithms.

Bandwidth guaranteed restorable multicast virtual private networks

We propose heuristic algorithms to compute optimized tunnel paths between single source and multiple destinations in a multicast VPN scenario. This is achieved by first building up a CPE based layout for the minimal cost (MC) multicast VPN problem and then selecting few core routers strategically. These we call active paths. We also compute backup paths for every active path for the sake of restorability, allowing sharing of backup bandwidth. This is also a type of online routing problem. For comparison purposes, we also formulate a mathematical model of the MC-multicast VPN problem using integer linear programming and solve it using the CPLEX tool.

APLS: active protocol label switching

The current trend of increasing accessibility and reachability of the Internet has resulted in many new services at the application layer. The potential growth of services on the Internet is only restricted by the network technologies that realize the Internet. In particular, layer 3 technologies are conventionally inflexible and do not adapt well to rapid changes in the Internet environment. Service-oriented networks should be more user-focused, which includes providing mechanisms that show value to the network providers, service providers, and clients. The next generation networking technologies must not only excel in performance, but also in flexibility, control, and scalability. This paper introduces a new network architecture called active protocol label switching (APLS), which establishes a foundation offering the same level of performance and scalability as current label-switching architectures lack. All existing label-switching architectures position the label as a shim layer between layers 2 and 3. The major reason behind this is to make the architecture network protocol independent. However, in designing APLS we investigated the merit of a new concept: label switching over IP. Several other new concepts are introduced: virtual label space, micro-instruction architecture, and micro-policy based forwarding. We will also focus on how APLS can be combined with active programmable networks to offer services at an unprecedented level.