Gustavo Sousa Pavani

Distributed approaches for impairment-aware routing and wavelength assignment algorithms in GMPLS networks

This work proposes two different distributed strategies for provisioning lightpaths in the presence of optical physical-layer impairments in GMPLS networks. The first approach is a more classical one, which introduces new extensions to the OSPF-TE routing protocol. The other approach makes use of an Ant Colony Optimization (ACO) algorithm to adaptively calculate routes in the network by actively monitoring the aggregate optical power of each link. By using an analytical model to incorporate the constraints of the Amplified Spontaneous Emission (ASE) noise of the optical amplifiers into the routing, we demonstrate the effectiveness of our approaches by means of an illustrative numerical example.

Traffic Engineering and Restoration in Optical Packet Switching Networks by means of Ant Colony Optimization

In this paper, we propose an ACO-based algorithm that can adaptively balance the network load to mitigate congestion, and hence reduce the overall loss of packets in an OPS network. In addition, the proposed algorithm is fault-tolerant, with the recovery from a failed link or node starting even before detection and localization of the failure event. Since both routing and restoration rely on pheromone levels laid by ant-like agents, any failure will be promptly perceived by some ants, which will then try to circumvent the affected part of the network, thus adapting the routing to the new topology.

Key parameters for contention resolution in multi-fiber Optical Burst/Packet Switching nodes

Optical networking paradigms based on statistical multiplexing, such as Optical Burst Switching or Optical Packet Switching, require the adoption of suitable contention resolution mechanisms at the optical nodes due to packets/bursts attempting to get access to the shared output channel at the same time. In the most general case of multi-fiber output links, contentions are tried to be solved by exploiting different domains — namely space, wavelength and time — and by applying an optimal scheduling policy. This paper focuses on the key parameters that can be used to design and optimize an optical packet/burst contention resolution scheme and shows how such parameters should be correlated for a correct performance assessment, taking into account feasibility trade-offs due to limited optical buffering and wavelength conversion capability.

Routing and wavelength assignment with crankback re-routing extensions by means of ant colony optimization

Crankback re-routing extensions can offer significant improvements in the successful setup of Label Switched Paths (LSPs) by allowing new retries on alternate paths that circumvent blocked links or nodes. These extensions can be incorporated into a fully-distributed algorithm based on Ant Colony Optimization metaheuristics, taking advantage of its self-adapting, emergent behavior. By comparing with traditional fixed-alternate re-routing mechanisms, simulations have demonstrated that the proposed algorithm can efficiently mitigate lightpath blocking, both during normal operation and in case of network failure, by locally repairing failed LSP setups due to blocked/failed resources.

Grid Resource Management by means of Ant Colony Optimization

The use of a manageable optical network is an important requirement for the new advanced data-intensive grid applications that begin to emerge on the e-Science field. In this paper, we propose an ACO-based algorithm that can provision on-demand and dynamically lightpaths on a grid system. Indeed, the proposed algorithm can schedule jobs by discovering processing and network resources on the grid, assigning the job to a specific system and executing the job. This is achieved with the help of an integrated GMPLS control plane, which allows both resource monitoring and management of networking resources.

Restoration in wavelength-routed optical networks by means of ant colony optimization

Because of the distributed control of the network, the dynamic nature of the traffic and the unpredictability of a failure event, the flexibility and robustness of ant colony optimization (ACO) make it a suitable candidate for provisioning lightpaths in an optical network. In this work, we propose a fault-tolerant dynamic routing and wavelength assignment (RWA) algorithm based on the ACO framework, presenting its integration into the Generalized multi-protocol label switching (GMPLS) control plane. By simulating two different scenarios, we demonstrate the effectiveness of this algorithm when a single link or node failure occurs.

Adaptive routing and wavelength assignment with power constraints using Ant Colony Optimization

This work proposes a novel routing algorithm for transparent optical networks, which is based on the ant colony optimization (ACO) meta-heuristics. It takes into consideration the bit error rate (BER) of the connections that is derived from amplified spontaneous emission (ASE) noise accumulated along the lightpath. We implement a call admission control (CAC) to verify if a connection meets the following criteria: it has a BER below the maximum level, which is given by the sensitivity power at each component, and the total aggregate power on every network link is below a threshold, which is necessary to mitigate fiber non-linear effects. By using an integrated generalized multi-protocol label switching (GMPLS) control plane, we demonstrate the effectiveness of our proposed algorithm over a fixed-alternate routing scheme to reduce the overall blocking probability.

Addressing self-similarity in optical switching networks by means of ant colony optimization

In this work, we propose the use of an Ant Colony Optimization (ACO) algorithm to mitigate packet loss in an optical packet switching network that carries self-similar traffic, which is known to have a great impact in the buffer performance in terms of loss probability as exemplified in this work. By adaptively routing the packets and balancing the network load, we demonstrate by some simulations the effectiveness of this approach when compared with a shortest-path routing scheme, achieving a performance that is comparable to the Poisson traffic scenario in some cases. The proposed algorithm can be used as a viable alternative to traffic shaping techniques.

An implementation of an OSPF-TE to support GMPLS-controlled all-optical WDM networks

GMPLS-controlled all-optical networks are the promise to handle the increasing volume of IP traffic. The GMPLS routing and signaling protocols, mainly OSPF and RSVP, work in such a way that the route calculation for optical circuits does not take into account the label (lambda) availability. This is not optimal in terms of network usage and blocking probability of new circuits. To deal with this scenario, more efficient RWA algorithms could be used to calculate the route and the wavelength assignment at one time. These RWA engines need to know the optical topology in a way that is not described by the current OSPF standards. This paper proposes Traffic Engineering extensions to the OSPF protocol to enable the GMPLS control plane to take advantage of the most effective RWA classes. A prototype was developed and deployed in an optical-simulated copper-based network to verify its feasibility based on the bandwidth overhead generated in the control plane.

Analysis of Ant Colony Optimization-based routing in optical networks in the presence of byzantine failures

Byzantine failures during the execution of the routing algorithm may degrade or disrupt the normal operation of the network. Ant Colony Optimization (ACO)-based routing algorithms are especially vulnerable to those failures. In this work, we propose the use of crankback re-routing extensions associated to the ACO algorithm in wavelength-routed optical networks to deal with byzantine failures. We investigate three different byzantine failure scenarios: misdirection of forward ants, dropping of forward ants and dropping of backward ants. Those failures affect the routing information of the network, but they are very hard to detect and cannot be fully addressed by integrity and authentication techniques. Without any need for a byzantine failure detection mechanism, simulations have demonstrated that the proposed approach is effective in mitigating the impact on the blocking probability due to network nodes exhibiting a byzantine behavior.