Pere Vilà

Ant Colony Behaviour as Routing Mechanism to Provide Quality of Service

Quality of Service (QoS) guarantees must be supported in a network that intends to carry real-time and multimedia traffic effectively. The effort of satisfying the QoS different requirements of these applications has resulted in the proposals of several QoS-based frameworks, such as Integrated Services (IntServ) [1], Differentiated Services (DiffServ) [2], and Multi-Protocol Label Switching (MPLS) [6].

Enhancing MPLS QoS routing algorithms by using the network protection degree paradigm

IP based networks still do not have the required degree of reliability required by new multimedia services, achieving such reliability will be crucial in the success or failure of the new Internet generation. Most of existing schemes for QoS routing do not take into consideration parameters concerning the quality of the protection, such as packet loss or restoration time. In this paper, we define a new paradigm to develop new protection strategies for building reliable MPLS networks, based on what we have called the network protection degree (NPD). This NPD consists of an a priori evaluation, the failure sensibility degree (FSD), which provides the failure probability and an a posteriori evaluation, the failure impact degree (FID), to determine the impact on the network in case of failure. Having mathematical formulated these components, we point out the most relevant components. Experimental results demonstrate the benefits of the utilization of the NPD, when used to enhance some current QoS routing algorithms to offer a certain degree of protection.

Availability analysis of GMPLS connections based on physical network topology

This paper presents a study of connection availability in GMPLS over optical transport networks (OTN) taking into account different network topologies. Two basic path protection schemes are considered and compared with the no protection case. The selected topologies are heterogeneous in geographic coverage, network diameter, link lengths, and average node degree. Connection availability is also computed considering the reliability data of physical components and a well-known network availability model. Results show several correspondences between suitable path protection algorithms and several network topology characteristics.

Topology-focused availability analysis of basic protection schemes in optical transport networks

We present a novel study of the availability in optical networks based on network topology. Connection availability is studied under two basic path protection schemes. Different topologies are selected in order to have heterogeneity in geographic coverage, network diameter, link lengths, and average node degree. Connection availability is also computed considering the reliability data of physical components and a well-known network availability model. Results report some useful information to select the suitable protection algorithms according to the network topology features and the required levels of availability.

ATM network management based on distributed artificial intelligence architecture

In this paper, we describe a multi-agent architecture for Virtual Path (VP) management (i.e. bandwidth and restoration) in Asynchronous Transfer Mode (ATM) networks. The intention is not to propose new strategies, but to improve the management integrating these different management mechanisms by using distributed artificial intelligence. Major objectives are scalability and robustness of the system. Our approach uses two different multi-agent systems. The first one consists of simple and small reactive agents that control and monitor the network elements (nodes and virtual path). The second one is another multi-agent system of more complex agents that monitors and controls the previous ones, while it is also allowed to change the allocated resources.

Multicast Extension of Unicast Charging for QoS Services

In order to successfully deploy multicast services in QoS-aware networks, pricing architectures must take into account the particular characteristics of multicast sessions. With this objective, we propose a charging scheme for QoS multicast services, assuming that the unicast cost of each interconnecting link is determined and that such cost is expressed in terms of quality of service (QoS) parameters. Our scheme allows determining the cost distribution of a multicast session along a cost distribution tree (CDT), and basing such distribution in those pre-existing unicast cost functions. The paper discusses in detail the main characteristics of the problem in a realistic interdomain scenario and how the proposed scheme would contribute to its solution

Efficient Routing in Data Center with Underlying Cayley Graph

Nowadays data centers are becoming huge facilities with hundreds of thousands of nodes, connected through a network. The design of such interconnection networks involves finding graph models that have good topological properties and that allow the use of efficient routing algorithms. Cayley Graphs, a kind of graphs that represents an algebraic group, meet these properties and therefore have been proposed as a model for these networks. In this paper we present a routing algorithm based on Shortlex Automatic Structure, which can be used on any interconnection network with an underlying Cayley Graph (of some finite group). We show that our proposal computes the shortest path between any two vertices with low time and space complexity in comparison with traditional routing algorithms.

Improving the Resilience of Transport Networks to Large-scale Failures

Telecommunication networks have to deal with fiber cuts, hardware malfunctioning and other failures on a daily basis, events which are usually treated as isolated and unrelated. Efficient methods have been developed for coping with such common failures and hence users rarely notice them. Although less frequently, there also arise cases of multiple failures with catastrophic consequences. Multiple failures can occur for many reasons, for example, natural disasters, epidemic outbreaks affecting software components, or intentional attacks. This article investigates new methods for lessening the impact of such failures in terms of the number of connections affected. Two heuristic-based link prioritization strategies for improving network resilience are proposed. One strategy is built upon the concept of betweenness centrality, while the second is based on what we call the observed link criticality. Both strategies are evaluated through simulation on a large synthetic topology that represents a GMPLS-based transport network. The provisioning of connections in a dynamic traffic scenario as well as the occurrence of large-scale failures are simulated for the evaluation.

Geometric Routing With Word-Metric Spaces

As a potential solution to the compact routing problem, geometric routing has been proven to be both simple and heuristically effective. These routing schemes assign some (virtual) coordinates in a metric space to each network vertex through the process called embedding. By forwarding packets to the closest neighbor to the destination, they ensure a completely local process with the routing table bounded in size by the maximum vertex degree. In this letter, we present an embedding of any finite connected graph into a metric space generated by algebraic groups, and we prove that it is greedy (guaranteed packet delivery). Then, we present a specialized compact routing scheme relying on this embedding for scale-free graphs. Evaluation through simulation on several Internet topologies shows that the resulting stretch remains below the theoretical upper bounds.

An ATM distributed simulator for network management research

Due to the high cost of a large ATM network working up to full strength to apply our ideas about network management, i.e., dynamic virtual path (VP) management and fault restoration, we developed a distributed simulation platform for performing our experiments. This platform also had to be capable of other sorts of tests, such as connection admission control (CAC) algorithms, routing algorithms, and accounting and charging methods. The platform was posed as a very simple, event-oriented and scalable simulation. The main goal was the simulation of a working ATM backbone network with a potentially large number of nodes (hundreds). As research into control algorithms and low-level, or rather cell-level methods, was beyond the scope of this study, the simulation took place at a connection level, i.e., there was no real traffic of cells. The simulated network behaved like a real network accepting and rejecting SNMP ones, or experimental tools using the API node.