Ole Brun Madsen

Topological routing in large-scale networks

A new routing scheme, Topological Routing, for large-scale networks is proposed. It allows for efficient routing without large routing tables as known from traditional routing schemes. It presupposes a certain level of order in the networks, known from. Structural QoS. The main issues in applying Topological Routing to large-scale networks are discussed. Hierarchical extensions are presented along with schemes for shortest path routing, fault handling and path restoration. Further research in the area is discussed and perspectives on the prerequisites for practical deployment of Topological Routing in large-scale networks are given.

Applying 4-regular grid structures in large-scale access networks

4-Regular grid structures have been used in multiprocessor systems for decades due to a number of nice properties with regard to routing, protection, and restoration, together with a straightforward planar layout. These qualities are to an increasing extent demanded also in large-scale access networks, but concerning protection and restoration these demands have been met only to a limited extent by the commonly used ring and tree structures. To deal with the fact that classical 4-regular grid structures are not directly applicable in such networks, this paper proposes a number of extensions concerning restoration, protection, scalability, embeddability, flexibility, and cost. The extensions are presented as a tool case, which can be used for implementing semi-automatic and in the longer term full automatic network planning tools.

Performance Evaluation of Impairment-Aware Routing Under Single- and Double-Link Failures

This work evaluates the performance of an impairment-aware routing (IAR) scheme in the presence of single- and dual-link failures. Network resilience is provided through a shared backup path protection scheme, enhanced with a reinforced sharing mechanism. The results indicate that the IAR scheme provides significantly lower connection blocking compared with traditional minimum-hop routing because physical impairments have a significant contribution to the overall network blocking probability. Dual-link failures are also considered, and the performance of a network designed to be resilient to single-link failures is evaluated. Simulation results show low connection loss rates due to dual failures that can be further improved using a restoration mechanism activated on the occurrence of dual failures.

Increasing the cost-constrained availability of WDM networks with degree-3 structured topologies

This paper studies the impact of node degree distribution to availability and capital and deployment expenditure of optical WDM transport networks. Three structured degree-3 graphs with fair node degree distribution are proposed in this context. Using a realistic network optimization framework based on genetic algorithms, we evaluate the performance of structured topologies and compare it against a practical topology (NSFNET). The results manifest that nodal degree fairness leads to increased availability compared to conventional topologies, while not incurring higher capital and deployment cost.

Multilevel network characterization using regular topologies

Multilevel networks have been a good solution in large-scale networks scenarios. The implementation of a network into different levels or sub-layers improves the performance and reduces the investment against plain topologies. This paper tries to characterize important parameters on multilevel networks such as diameter, average distance and gateway location to be able to optimize the global network topology with no need for additional path calculations. The study focuses on the lower level of the network formed by subnetworks with regular structures such as Single Ring, Double Ring and Torus Grid. The achieved results will ease and improve the network planning of large-scale networks.

Improving topological routing in N2R networks

Topological routing is basically table free, and allows for very fast restoration and thus a high level of reliability in communication. It has already been satisfactorily proposed for some regular structures such as Grid or Honeycomb. An initial proposal has also been developed for the N2R structures. This paper proposes a modification of this previous algorithm, and in addition two other alternatives. The three options are systematically analyzed in terms of executing time and path distances, showing that trade-offs are needed in order to determine which algorithm is best for a given case. Also, the possible practical applications the methods could have, are discussed for different traffic scenarios.

Combining wired and wireless networks for a QoS-aware broadband infrastructure

We show how integrated planning of wired and wireless infrastructures can be used to build a QoS-aware broadband infrastructure. The outset is a case study of the municipality of Hals, a rural community in Denmark, where the objective is to establish a broadband infrastructure reaching all households and businesses. Two factors are considered particularly important when designing an infrastructure: the chosen technology must allow for sufficient bandwidth, and the physical network structures must allow for independent paths between any pair of nodes. A final solution is obtained by using fiber to the home for primary connections and fixed wireless access for backup. This is implemented over 15 years, during which temporary solutions ensure sufficient QoS and reliability for all users. These temporary solutions form parts of the final solutions.

Hybrid distributed iterative capacity allocation over Bluetooth network

With the current development of mobile devices, short range wireless communications have become more and more popular, and many researches on short range wireless communications, such as Bluetooth, have gained special interests, in industry as well as in academy. This paper analyzes capacity allocation issues in Bluetooth network as a convex optimization problem. We formulate the problem of maximizing the total network flows and minimizing the costs of flows. The hybrid distributed capacity allocation scheme is proposed as an approximated solution of the formulated problem that satisfies quality of service requirements and constraints in Bluetooth network, such as limited capacity, decentralized, frequent changes of topology and of capacities assigned to nodes in the network. The simulation shows that the performance of Bluetooth could be improved by applying the hybrid distributed iterative capacity allocation scheme.

Impact of dual-link failures on impairment-aware routed networks

This paper evaluates the impact of dual-link failures on single-link failure resilient networks, while physical layer constraints are taken into consideration during demand routing, as dual link failures and equivalent situations appear to be quite probable in core optical networks. In particular, a shared backup path protection scheme is used as a basis and an impairment-aware routing scheme is compared against classical minimum hop routing. Both approaches employ impairment-aware routing on the primary path, while impairment-aware is compared to min-hop on the backup path. The main metric used to illustrate the performance of the two schemes is the blocking occurring in the process of restoring the established connections that are affected by a dual-link failure. Simulation results show low restoration blocking, thus high ability of a single-failure resilient network to handle dual link failures, identifying the impairment-aware scheme as the choice of preference for both primary and backup paths when the path quality has to be considered.

A Framework for Planning a Unified Wired and Wireless ICT Infrastructure

The increase in the use of information and communication technology (ICT) has pushed the existing access networks to their limits. Whole new access networks are currently being deployed and are expected to fully support the already started synergy of services converging on to one network. Through a brief survey of synergy and technology trends, it is concluded that a future network will use wired and wireless as complementary technologies. In this context the paper proposes a framework for planning of unified wired and wireless ICT infrastructures. The framework includes different input parameters of relevance for the planning and implementation, which also include a step-wise implementation plan. Planning methods for wired and wireless planning is presented and a simplified large-scale case study is conducted to verify and illustrate the use of the framework. The framework is concluded to be useful and the discussion lists some areas for further consideration.