Lluís Fàbrega

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 fault management performance of two-step QoS routing algorithms in GMPLS networks

In this paper a novel methodology aimed at minimizing the probability of network failure and the failure impact (in terms of QoS degradation) while optimizing the resource consumption is introduced. A detailed study of MPLS recovery techniques and their GMPLS extensions are also presented. In this scenario, some features for reducing the failure impact and offering minimum failure probabilities at the same time are also analyzed. Novel two-step routing algorithms using this methodology are proposed. Results show that these methods offer high protection levels with optimal resource consumption.

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.

A review of the architecture of admission control schemes in the Internet

Admission Control (AC) is an efficient way of dealing with congestion situations in a network. Using AC, when network resources in a path are not enough for all flows (i.e., during congestion), some of the flows receive the requested service and the rest do not. Congestion situations can be reduced by increasing network resources or by optimizing their use through better routing techniques, but if congestion still occurs, AC achieves efficient use of network resources by maximizing the number of satisfied flows. However, using AC complicates the network scheme, and therefore a major concern is making the AC as simple as possible. In this paper we review the main AC schemes that have been proposed for the Internet, focusing on the simplicity of their architectures in terms of the number of nodes that participate in the AC, the required state, the use of signaling, and others.

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.

Cayley-Graph-Based Data Centers and Space Requirements of a Routing Scheme Using Automata

Modern data centers connect tens of thousands of computers by an interconnection network. The design of such networks implies the selection of an appropriate routing scheme for them. Those schemes need to be efficient with respect to time and space requirements. Cayley Graphs (CG) has been proposed as models for large-scale interconnection networks with excellent properties and very efficient routing schemes. In a previous work, we presented a fast general-purpose shortest path routing scheme for CG with compact routing tables. The scheme uses the concept the Automatic Structures (AS) of a group. However, the size of such structures was not considered into the complexity analysis. Therefore, this paper evaluates the required space to keep such structures and the several intermediate finite state automata that arise during the process of constructing such AS. We perform the evaluation on six well-known families of CG. The results show which structures are space-efficient to implement the scheme, and how the size of such structures depends on the so-called k-fellow traveler property.

Throughput guarantees for elastic flows using end-to-end admission control

Internet applications such as web or ftp will be satisfactorily supported by a guaranteed minimum throughput service. We propose to build this service in a core-stateless network such as Differentiated Services with an Admission Control (AC) method based on end-to-end measurements, using the first packets of the flow. The whole scheme uses a small set of packet classes (with different discarding priorities), and is therefore simple and scalable. We evaluate the scheme through simulations in several scenarios using TCP flows. Finally, we propose an extension of the method aimed at improving its performance.

Measurement Methodology and Tools

Aiming at creating a dynamic between elaboration, realization, and validation by means of iterative cycles of experimentation, Future Internet Research and Experimentation (FIRE) projects have been rapidly confronted to the lack of systematic experimental research methodology. Moreover, the “validation by experimentation” objective involves a broad spectrum of experimentation tools ranging from simulation to field trial prototypes together with their associated measurement tools. As experimental measurement results and corresponding tools play a fundamental role in experimental research, devising a systematic experimentation and measurement methodology becomes thus crucial for experimental research projects to achieve this objective for their various realizations, including protocols, systems and components. In turn, and in order to meet scientific validity criteria, the measurement results obtained when performing experimental research implies the availability of reliable and verifiable measurement tools, including on-line measurement data analysis and mining.

Network schemes for TCP elastic traffic in the Internet

TCP elastic traffic is generated by the traditional “data” applications in the Internet, such as web browsing, peer-to-peer file sharing, ftp, e-mail and other. These applications are built on top of TCP, which provides reliable transfers and adjusts the sending rate to the network conditions to achieve the maximum possible throughput, a feature that makes TCP flows to be called “elastic”. From the point of view of the network, TCP elastic traffic requires the maximum possible throughput above a minimum value, a network service that we call the Minimum Throughput Service (MTS). In this paper we survey the main network schemes that have been proposed in the Internet to provide this service for TCP elastic traffic, classified in two broad groups, the ones that do not use Admission Control (AC) and the ones that do use it. For each network scheme we describe the main characteristics of the service (whether the minimum throughput can be different or is the same for all flows, whether isolation among flows is provided, etc.) and their architecture (the specific traffic conditioning, queue disciplines and AC mechanisms used, the required state, the use of signaling, etc.).