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

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

On optimal computation of MPLS label binding for multipoint-to-point connections

Most network operators have considered reducing Label Switched Routers (LSR) label spaces (i.e. the number of labels that can be used) as a means of simplifying management of underlaying Virtual Private Networks (VPNs) and, hence, reducing operational expenditure (OPEX). This letter discusses the problem of reducing the label spaces in Multiprotocol Label Switched (MPLS) networks using label merging - better known as MultiPoint-to-Point (MP2P) connections. Because of its origins in IP, MP2P connections have been considered to have tree- shapes with Label Switched Paths (LSP) as branches. Due to this fact, previous works by many authors affirm that the problem of minimizing the label space using MP2P in MPLS - the Merging Problem - cannot be solved optimally with a polynomial algorithm (NP-complete), since it involves a hard- decision problem. However, in this letter, the Merging Problem is analyzed, from the perspective of MPLS, and it is deduced that tree-shapes in MP2P connections are irrelevant. By overriding this tree-shape consideration, it is possible to perform label merging in polynomial time. Based on how MPLS signaling works, this letter proposes an algorithm to compute the minimum number of labels using label merging: the Full Label Merging algorithm. As conclusion, we reclassify the Merging Problem as Polynomial-solvable, instead of NP-complete. In addition, simulation experiments confirm that without the tree-branch selection problem, more labels can be reduced

Full label space reduction in MPLS networks: asymmetric merged tunneling

Traffic Engineering objective is to optimize network resource utilization. Although several works have been published about minimizing network resource utilization in MPLS networks, few of them have been focused in LSR label space reduction. This letter studies Asymmetric Merged Tunneling (AMT) as a new method for reducing the label space in MPLS network. The proposed method may be regarded as a combination of label merging (proposed in the MPLS architecture) and asymmetric tunneling (proposed recently in our previous works). Finally, simulation results are performed by comparing AMT with both ancestors. They show a great improvement in the label space reduction factor

Label Space Reduction in MPLS Networks: How Much Can A Single Stacked Label Do?

Most network operators have considered reducing LSR label spaces (number of labels used) as a way of simplifying management of underlaying virtual private networks (VPNs) and therefore reducing operational expenditure (OPEX). The IETF outlined the label merging feature in MPLS-allowing the configuration of multipoint-to-point connections (MP2P)-as a means of reducing label space in LSRs. We found two main drawbacks in this label space reduction a)it should be separately applied to a set of LSPs with the same egress LSR-which decreases the options for better reductions, and b)LSRs close to the edge of the network experience a greater label space reduction than those close to the core. The later implies that MP2P connections reduce the number of labels asymmetrically

All-Optical Label Stacking: Easing the Trade-offs Between Routing and Architecture Cost in All-Optical Packet Switching

All-optical label swapping (AOLS) forms a key technology towards the implementation of all-optical packet switching nodes (AOPS) for the future optical Internet. The capital expenditures of the deployment of AOLS increases with the size of the label spaces (i.e. the number of used labels), since a special optical device is needed for each recognized label on every node. Label space sizes are affected by the way in which demands are routed. For instance, while shortest-path routing leads to the usage of fewer labels but high link utilization, minimum interference routing leads to the opposite. This paper studies all-optical label stacking (AOLStack), which is an extension of the AOLS architecture. AOLStack aims at reducing label spaces while easing the compromise with link utilization. In this paper, an integer lineal program is proposed with the objective of analyzing the softening of the aforementioned trade-off due to AOLStack. Furthermore, a heuristic aiming at finding good solutions in polynomial-time is proposed as well. Simulation results show that AOLStack either a) reduces the label spaces with a low increase in the link utilization or, similarly, b) uses better the residual bandwidth to decrease the number of labels even more

Partial disjoint path for multi-layer protection in GMPLS networks

In this paper, different recovery methods applied at different network layers and time scales are used in order to enhance the network reliability. Each layer deploys its own fault management methods. However, current recovery methods are applied to only a specific layer. New protection schemes, based on the proposed partial disjoint path algorithm, are defined in order to avoid protection duplications in a multi-layer scenario. The new protection schemes also encompass shared segment backup computation and shared risk link group identification. A complete set of experiments proves the efficiency of the proposed methods in relation with previous ones, in terms of resources used to protect the network, the failure recovery time and the request rejection ratio

Enhanced multi-layer protection in multi-service GMPLS networks

This paper focuses on QoS routing with protection in an MPLS network over an optical layer. In this multi-layer scenario each layer deploys its own fault management methods. A partially protected optical layer is proposed and the rest of the network is protected at the MPLS layer. New protection schemes that avoid protection duplications are proposed. Moreover, this paper also introduces a new traffic classification based on the level of reliability. The failure impact is evaluated in terms of recovery time depending on the traffic class. The proposed schemes also include a novel variation of minimum interference routing and shared segment backup computation. A complete set of experiments proves that the proposed schemes are more efficient as compared to the previous ones, in terms of resources used to protect the network, failure impact and the request rejection ratio

Adding new components to the knowledge plane GMPLS over WDM networks

A recent study defines a new network plane: the knowledge plane. The incorporation of the knowledge plane over the network allows having more accurate information of the current and future network states. In this paper, the introduction and management of the network reliability information in the knowledge plane is proposed in order to improve the quality of service with protection routing algorithms in GMPLS over WDM networks. Different experiments prove the efficiency and scalability of the proposed scheme in terms of the percentage of resources used to protect the network

[Ressenya del llibre Rediscovering geography: new relevance for science and society, de Rediscovering Geography Committee, National Research Council]

El llibre ressenyat pretén ser una síntesi i una avaluació de la situació de la geografia als Estats Units. Estructurat en vuit capítols, els sis primers són una anàlisi de diversos aspectes de la geografia i els dos últims expliquen quina estratègia hauria de portar-se a terme per enfortir el paper de la geografia en el món acadèmic i en la societat en general

[Ressenya del llibre La sociabilitat epistolar de la família Burgués de Girona (1799-1803)]

Ressenya del llibre La sociabilitat epistolar de la família Burgués de Girona (1799-1803). Es tracta d’un epistolari adreçat a un noble de rang menor i d’àmbit local, en aquest cas Girona. La intenció de l’editor és formulada ben explícitament: «Obrir una finestra al passat i posar a l’abast dels investigadors i de les persones interessades i curioses un recull de les pràctiques socials, culturals, familiars, relacionals i literàries d’una família noble de la ciutat de Girona en el trànsit del segle XVIII al segle XIX»

Richard Rorty i una aproximació pragmatista al liberalisme polític de John Rawls

Aquest article es proposa explorar la possibilitat d'apropar a la concepció del liberalisme polític metafilosòfic de John Rawls des del punt de vista pragmatista de Richard Rorty. La proposta està motivada per les similituds que es poden observar entre elles respecte de la finalitat i la sortida d'una concepció política. El resultat final de l'article és ambigua: d'una banda, no sembla tan descabellat afirmar que la teoria de Rawls es pot llegir sense més dificultats des d'una perspectiva pragmàtica, d'altra banda, hi ha alguns aspectes importants en els quals un liberalisme polític de Rawls segueix sent incompatible amb una concepció política de Rorty

Ideologia, política i llenguatge de classes en el primer sindicalisme, 1840-1870

Estudi del sindicalisme a Espanya des dels seus orígens i fins el 1870. L’autor planteja dues qüestions: la ideologia elaborada pel sindicalisme entre 1840 i 1856, i en segon lloc alguns aspectes de les relacions entre sindicalisme i política, i l’elaboració d’un llenguatge de classes

Noves aportacions a l'estudi dels orígens de Gerunda

Revisió de les teories sobre els orígens de Gerunda. Es tracten aspectes com ara el nom de la ciutat, la situació topogràfica i la planta del municipi romà, la localització sobre el perímetre emmurallat que envolta la ciutat romana i la troballa de ceràmica indígena anterior a la conquesta romana

Noves llums sobre la Guerra de Successió [Ressenya del llibre Els catalans i Felip V: De la conspiració a la revolta, 1700-1705, de Joaquim Albareda i Salvadó]

Historiografia de la guerra catalana de Successió. El llibre que ressenya va obtenir el IV Premi Internacional Jaume Vicens Vives de Ciències Socials