Joan Triay

From Delay-Tolerant Networks to Vehicular Delay-Tolerant Networks

This paper provides an introductory overview of Vehicular Delay-Tolerant Networks. First, an introduction to Delay-Tolerant Networks and Vehicular Delay-Tolerant Networks is given. Delay-Tolerant schemes and protocols can help in situations where network connectivity is sparse or with large variations in density, or even when there is no end-to-end connectivity by providing a communications solution for non real-time applications. Some special issues like routing are addressed in the paper and an introductory description of applications and the most important projects is given. Finally, some research challenges are discussed and conclusions are detailed.

An ant-based algorithm for distributed routing and wavelength assignment in dynamic optical networks

Future optical communication networks are expected to change radically during the next decade. To meet the demanded bandwidth requirements, more dynamism, scalability and automatism will need to be provided. This will also require addressing issues such as the design of highly distributed control plane systems and their associated algorithms to respond to network changes very rapidly. In this work, we propose the use of an ant colony optimization (ACO) algorithm to solve the intrinsic problem of the routing and wavelength assignment (RWA) on wavelength continuity constraint optical networks. The main advantage of the protocol is its distributed nature, which provides higher survivability to network failures or traffic congestion. The protocol has been applied to a specific type of future optical network based on the optical switching of bursts. It has been evaluated through extensive simulations with very promising results, particularly on highly congested scenarios where the load balancing capabilities of the protocol become especially efficient. Results on a partially meshed network like NSFNET show that the ant-based protocol outperforms other RWA algorithms under test in terms of blocking probability without worsening other metrics such as mean route length.

Time shared optical network (TSON): A novel metro architecture for flexible multi-granular services

This paper presents the TSON metro mesh network architecture for guaranteed, statistically-multiplexed services. It proposes tunable time-wavelength assignment, one-way tree-based reservation and node architecture. Results demonstrate high network efficiency, fast service delivery and guaranteed QoS.

Dynamic Anycast Routing and Wavelength Assignment in WDM Networks Using Ant Colony Optimization (ACO)

Ant colony optimization (ACO) is a probabilistic technique used for solving complex computational problems, such as finding optimal routes in networks. It has been proved to perform better than simulated annealing and genetic algorithm approaches for solving dynamic problems. ACO algorithms can quickly adapt to real-time changes in the system. In this paper, we propose an ACO-based algorithm to solve the dynamic anycast routing and wavelength assignment (RWA) problem in wavelength-routed WDM networks. Using extensive simulations, we show that ACO-based anycast RWA significantly reduces blocking probability compared to the fixed shortest-path first (SPF) and other dynamic algorithms.

Demonstration of C/S based hardware accelerated QoT estimation tool in dynamic impairment-aware optical network

An enhanced version of hardware accelerated QoT estimation tool in impairment-aware optical network is demonstrated and evaluated against the different number of lightpaths and wavelengths per link. It outperforms the software version by 28 times in the order of millisecond.

Analytical blocking probability model for hybrid immediate and advance reservations in optical WDM networks

Immediate reservation (IR) and advance reservation (AR) are the two main reservation mechanisms currently implemented on large-scale scientific optical networks. They can be used to satisfy both provisioning delay and low blocking for delay-tolerant applications. Therefore, it seems reasonable that future optical network provisioning systems will provide both mechanisms in hybrid IR/AR scenarios. Nonetheless, such scenarios can increase the blocking of IR if no quality-of-service (QoS) policies are implemented. A solution could be to quantify such blocking performance based on the current network load and implement mechanisms that would act accordingly. However, current blocking analytical models are not able to deal with both IR and AR. In this paper, we propose an analytical model to compute the network-wide blocking performance of different IR/AR classes within the scope of a multiservice framework for optical wavelength-division multiplexing (WDM) networks. Specifically, we calculate the blocking on two common optical network scenarios using the fixed-point approximation analysis: on wavelength conversion capable and wavelength-continuity constrained networks. Performance results show that our model provides good accuracy compared to simulation results, even in a scenario with multiple reservation classes defined by different book-ahead times.

Distributed contention avoidance in Optical Burst-Switched ring networks

Optical burst switching (OBS) is a promising technology for future optical networks. Due to its less complicated implementation using current optical and electrical components, OBS is seen as the first step towards the future optical packet switching (OPS). Regarding network topologies, the ring is extensively used on current metropolitan environments, and this does not seem it will change in the foreseeable future. In this paper we propose a new medium access protocol for optical burst-switched networks over metropolitan rings that enables the nodes to access the channel in a distributed way. This new protocol avoids burst blockings in transit nodes, turning itself into an efficient and simple burst contention avoidance mechanism. The use of this protocol maximizes the throughput of the network without deteriorating excessively other parameters such as end-to-end delay or ingress queues.

On extending ESnet's OSCARS with a multi-domain anycast service

Current scientific data applications require advanced network provisioning systems to support the transport of large volumes of data. Due to the availability of diverse computing and Grid clusters, these applications can benefit from anycasting capabilities. In contrast to unicasting, anycast routing allows the selection of a node from a group of candidate destinations. This new means of communication allows for greater routing flexibility and better network resource consumption. However, current provisioning systems do not provide fully compliant anycast implementations. In this paper, we extend ESnets OSCARS virtual circuit provisioning system with anycast routing capabilities to support destination-agnostic applications on single- and multi-domain network scenarios. The proposed implementation significantly improves provisioning success over the native unicast implementation in compliance with the existing OSCARS framework.

Integration of Optical and Wireless Technologies in the Metro-Access: QoS Support and Mobility Aspects

Future metropolitan and access networks are expected to comprise heterogeneous optical and broadband wireless technologies. The growing demand of users for transparent, ubiquitous access to diverse communication services poses several challenges. We envision a future metro-access architecture that comprises Optical Burst Switching networks that feed Ethernet Passive Optical Networks (PON) or upcoming Wavelength-Division Multiplexing PON, which in turn feed IEEE 802.16 and IEEE 802.11 nodes. Nodes in the wireless realm may communicate in a multihop fashion, forming mesh networks. To maintain cost and resource efficiency, we propose the introduction of Quality of Service (QoS) proxies at the border between different link technologies. These entities handle QoS requirements and aid to the support of mobility. The architecture requires no modification of the Medium Access Control mechanisms of the different technologies.

An ant-based algorithm for distributed RWA in optical burst switching

To meet the demanded bandwidth requirements of future optical communication networks, more dynamism, scalability and automatism will need to be provided, which will require, as well, new control plane designs to respond to network changes very rapidly. In this work, we propose the use of an ant colony optimization (ACO) algorithm to support the routing and wavelength assignment in wavelength continuity constraint optical burst-switched networks. The main advantage of the protocol is its distributed nature, which provides higher survivability to network failures or traffic congestion. From the results we see that the new protocol responds effectively to congestion while at the same time providing better performance in comparison to the shortest path routing with random wavelength assignment.