Capital Controls and Monetary Policy in Developing Countries

This paper looks at both the theoretical and empirical literature on capital controls and finds that capital controls can play an important role in developing countries by helping to insulate them from some of the harmful effects of volatile and short-term capital flows. The authors look at controls on capitalinflows in Malaysia (1989-1995); Colombia (1993-1998); Chile (1989-1998); and Brazil (1992-1998), and also consider the case of Malaysia’s controls on outflows in 1998-2001. They conclude that there is sufficient backing in both economic theory and empirical evidence to consider more widespread adoption of capital controls in order to address some of the macroeconomic problems associated with short-term capital flows, to enable certain development strategies, and to allow policy makers more flexibility with regard to crucial monetary and exchange rate policies.capital controls, capital flows

On MPR-OSPF Specification and Implementation in Quagga/GTNetS

This document analyses the MPR-OSPF current specification and compares it with the implemented version for the Quagga / Zebra routing suite, adapted for the GTNetS network simulator. It presents the relationship between Quagga/Zebra core and the GTNetS simulation framework, describes the inner architecture of the MPR-OSPF extension in the OSPF Quagga general implementation and identifies the different protocol main elements in the implemented code

La mediación de la información en Internet: evolución, tendencias y riesgos

La expansión de Internet está modificando la estructura y la dinámica del espacio mediático en las sociedades en las que está presente. En poco tiempo, ha adquirido una enorme importancia como cauce de circulación y contraste de información, espacio de discusión y debate público, marco de formación de la opinión colectiva y, de manera embrionaria pero cada vez más nítida, instrumento de movilización social y acción política. Las expectativas y esperanzas depositadas en Internet han sido muy elevadas. Simplificando, la “promesa de Internet” ha consistido en hacer posible una comunicación y un acceso a la información no mediados, y, en consecuencia, en reducir el poder de los grandes operadores mediáticos. No obstante, las transformaciones observables en Internet en los últimos años, en buena parte ligadas a la emergencia del llamado «Internet de los contenidos», sugieren que el futuro de la red de redes podría orientarse en sentido contrario, hacia un modelo de red más persuasiva y más mediada, en la que la influencia de nuevos operadores mediáticos podría incrementarse y conferirles, por tanto, mayor capacidad para condicionar los procesos de conformación de la opinión pública. Este artículo recorre algunos de los principales cambios tecnológicos en curso en Internet y examina su posible impacto sobre la autonomía y la capacidad de elección de los usuarios, por un lado, y sobre el ideal de libre información, comunicación directa y no mediada que en su momento constituyó el núcleo del diseño de Internet, por otro. The expansion of the Internet is significantly modifying both the structure and dynamics of the news media, especially in those societies where it is more present. In a short time, the Internet has become a relevant channel for information flow, fact checking, and public discussion, as well as an increasingly important space for public opinion formation. More recently, it has also been used a means for social mobilization and political action. Expectations and hopes around the Internet have been extremely high. In short, the“Internetpromise”hasconsistedonproviding free information access and non-mediated communication, thereby dramatically reducing the power of hegemonic media. However, ongoingtransformations,especiallythoserelated to the so-called “content-centric Internet”, rather suggest that its evolution may point to the opposite direction, towards a more persuasive, increasingly mediated network, in which the power of the news media would increase —rather than decrease—, and would therefore provide them with a more prominent role in public opinion formation process. This paper examines some of the most relevant technological changes that are taking place in the Internet and discusses their possible impact on the autonomy and freedom of final users, on the one hand, and the ideal of free information access and direct and non-mediated communication that was at the core of the Internet original architecture, on the other.

Adjacency Persistency in OSPF MANET

Link-state routing remains as one of the most challenging issues in ad hoc networking, due to the special conditions and requirements that hold in such networks, which cannot be handled by classical routing protocols. In the last decade, several efforts have been deployed either to design new routing solutions adapted to ad hoc conditions, either to extend existing solutions for wired networks to the domain of wireless mobile scenarios. This paper elaborates on the latter alternative, focusing on the standard OSPF MANET extension RFC 5449. It analyzes the impact and interest of the persistency principle to the main OSPF MANET operations, in particular the adjacency synchronization and the other operations that relate to it (flooding and route construction). The presented results show that such persistent approach is appropriate for managing adjacencies in the context of RFC 5449, and significant improvements might be achieved by extending the persistent principle into the topology selection mechanism.Le routage d'état-lieu (link-state) reste comme l'une des questions les plus difficiles dans un réseau ad hoc, en raison des conditions particulières et des exigences qui tiennent à de tels réseaux, qui ne peuvent êre traitées par les protocoles de routage classiques. Dans la dernière décennie, plusieurs efforts ont été déployés, soit pour concevoir de nouvelles solutions de routage adaptées aux conditions ad hoc, soit pour étendre les solutions existantes pour les réseaux filaires au domaine des scénarios wireless mobiles. Ce document détaille la dernière alternative, en se concentrant sur l'extension standard RFC 5449 OSPF MANET. Il analyse l'impact et l'intérêt du principe de "persistance" sur des opérations principales au context OSPF MANET, en particulier la synchronisation des adjacences et les autres opérations qui s'y rapportent (flooding et construction de routes). Les résultats présentés montrent que cette approche persistante est appropriée pour la gestion des adjacences dans le cadre du RFC 5449, et des améliorations significatives peuvent être obtenues en étendant le principe de "persistance" au mécanisme de sélection topologique

MPR-based Pruning Techniques for Shortest Path Tree Computation

Multi-Point Relaying (MPR) is a well-known relay pruning algorithm that has proved to be useful for efficient dissemination in Mobile Ad hoc Networks (MANETs). But this technique may be useful for other tasks in MANET link-state routing as well. In particular, the approach is attractive for the selection of topology information to be flooded across the network. Requirements for such topology selection are however different from those applying for efficient dissemination, so approaches in such direction need to address these requirements and adapt or complement the MPR mechanism accordingly. This paper analyzes the main asymptotic properties of MPR and MPR-based topology selection algorithms, and provides sufficient conditions for the correctness of MPR-based topology selection. It examines as well in detail the MPR-based topology selection algorithm of MPR-OSPF, Path MPR, and shows that this algorithm may be unable, in certain conditions, to preserve optimal routes in its topology selection. The paper concludes by proposing and validating a modification of the Path MPR algorithm to overcome this sub-optimal performance

Maximal slicings in spherical symmetry: local existence and construction

We show that any spherically symmetric spacetime locally admits a maximal spacelike slicing and we give a procedure allowing its construction. The construction procedure that we have designed is based on purely geometrical arguments and, in practice, leads to solve a decoupled system of first order quasi-linear partial differential equations. We have explicitly built up maximal foliations in Minkowski and Friedmann spacetimes. Our approach admits further generalizations and efficient computational implementation. As by product, we suggest some applications of our work in the task of calibrating Numerical Relativity complex codes, usually written in Cartesian coordinates.Comment: 25 pages, 6 figure

Wired/Wireless Compound Networking

International audienceThis chapter explores techniques that enable efficient link state routing on compound networks. These techniques rely on the selection and maintenance of a subset of links in the network (i.e. an overlay) along which the different operations of link-state routing can be performed more efficiently. This chapter provides a formal analysis of such techniques, a qualitative evaluation of their specific properties and example applications of such techniques with a standard routing protocol

A Theoretical Model for Analyzing the Impact of Jitter-based Techniques on Flooding over Wireless Ad Hoc Networks

Jitter is used in wireless ad hoc networks to reduce the number of packet collisions and the number of transmissions. This is done by scheduling random back-off for each packet to be transmitted and by piggybacking multiple packets in a single transmission. This technique has been standardized by the IETF in RFC 5148. This paper investigates on the impact of the standardized jitter mechanism on network-wide packet dissemination -- i.e. flooding, an important component for many protocols used today. A novel analytical model is introduced, capturing standard jitter traits. From this model is derived accurate characterization of the effects of jittering on flooding performance, including the additional delay for flooded packets on each traversed network interface, the reduction of the number of transmissions over each network interface, and the increased length of transmissions, depending on jitter parameters. This report also presents an analysis of the use of jitter in practice, over an 802.11 wireless link layer based on CSMA. The analytical results are then validated via statistical discrete event simulations. The report thus provides a comprehensive overview of the impact of jittering in wireless ad hoc networks.Le délai aléatoire, ou jitter, est utilisé dans les réseaux ad hoc pour réduire le numéro de collisions de paquet, aussi bien que le numéro de transmissions. Cela se fait en ajoutant un back-off aléatoire avant la retransmission de chaque paquet, et en envoyant plusieurs paquets d'une seule fois, en une seule transmission (piggybacking). Cette technique fût standardisée par l'IETF au RFC 5148. Ce rapport analyse l'usage et l'impact du mécanisme du jitter dans la dissémination de paquets à travers le réseau (flooding), qui est un composant importante de plusieurs protocoles, en particulier protocoles de routage, couramment utilisées aujourd'hui. Le rapport propose un nouvel modèle analytique qui capture et décrit les traits et caractéristiques principales du jitter. Depuis ce modèle, le rapport déduit l'effet du jittering sur la performance de l'opération de dissémination périodique ou flooding, notamment le délai additionnel souffert par les paquets disséminés à travers le réseau, la réduction du nombre de retransmissions par interface et la longueur des paquets retransmis, en fonction des paramètres du mécanisme de jitter. Le rapport étudie aussi l'usage pratique du jitter dans des réseaux sans fils, au-dessus de technologies 802.11, basées sur CSMA. Les résultats analytiques obtenus à traves de ce modèle théorique sont validés par moyen de simulations à évents discrets. En somme, le rapport offre une perspective générale sur l'effet des techniques de jitter dans des réseaux ad hoc sans fils

Compound Wired/Wireless Internetworking with OSPF

As wireless ad hoc networks become more deployed, there is a growing interest for compound internetworks, that is, internetworks that contain both fixed and ad hoc networks. Routing is one of the main challenges that arise in such compound internetworks. Although specialized routing protocols exist for wired and for ad-hoc networks, and several such specialized protocols could be used together in a compound internetwork, it has been shown that the use of a single routing solution in the whole internetwork brings several advantages. The IETF has standardized extensions of the Open Shortest Path First (OSPF) protocol for ad hoc operation. While previous performance evaluations of these extensions have focused on the wireless part of the internetwork and have been mostly performed by way of simulation tools, this paper studies practical issues of the use of a single protocol, extended OSPF, providing paths through a compound internetwork. In first term, it examines the behavior of OSPF in a real networking testbed. This testbed consists of an internetwork composed of 6 computers that form a static topology, \emph{i.e.}, computers do not move during network lifetime. In second term, the overall behavior of extended OSPF, both considering standard OSPF and its MANET extension, is examined. Despite the limitations of the testbed, these experiments provide both a proof-of-concept and complementary results compared to prior work in the domain, which was mostly based on simulations, and focused on wireless ad hoc network scenarios only.À mesure que les réseaux ad hoc sans fil deviennent de plus en plus déployés, il y a un intérêt croissant pour des internetworks (réseaux des réseaux) hybrides, c'est-à-dire, internetworks qui contiennent à la fois des réseaux ad hoc et des réseaux fixes. En ce domain-là, le routage est un des principaux défis qui se posent. Bien qu'il existe des protocoles de routage spécifiques pour réseaux filières et des réseaux sans fils et ad hoc, et plusieurs de ces protocoles pourraient être utilisés ensemble dans un internetwork hybride, il a été montré que l'utilisation d'une seule solution de routage dans un internetwork hybride a plusieurs avantages. L'IETF a standardisé trois extensions du protocole Open Shortest Path First (OSPF) ayant pour but le routage dans des réseaux ad hoc et à mobilité (MANETs). Les évaluations du rendement de ces extensions développées jusqu'à présent se sont concentrées sur la partie sans fil (ad hoc) de l'internetwork et ont été principalement effectuées à travers de simulations. Ce rapport étudie des questions pratiques liées a l'usage d'un seul protocol de routage, en l'occurrence OSPF, sur un internetwork hybride. D'abord, la performance de OSPF est analysée avec des experiénces sur un banc d'essai de réseaux (testbed). Ce testbed consiste en un internetwork hybride de 6 ordinateurs qui forment une topologie statique, c.-à.-d. où les ordinateurs ne bougent pas durant la vie du réseau. Deuxièmement, le comportement global du protocole OSPF étendu, à la fois sa version standard et son extension pour MANETs, est examiné. Malgré les limites du testbed, ces expériences fournissent à la fois une preuve de concept et des résultats qui confirment et complétent des travaux antérieurs dans le domaine, basés sur l'analyse du protocol sur MANETs à travers des simulations

Optimization of Critical Data Synchronization via Link Overlay RNG in Mobile Ad Hoc Networks

International audienceIn practice, ad hoc networks are still too unreliable for standard mobile and vehicular communications. It is thus important to complement current protocols in this context, with schemes guaranteeing the exchange of critical data when needed. A promising approach in this realm is to use an overlay subgraph, over which critical messages are exchanged and acknowledged in a peer to peer fashion. Overlay nodes' local databases remain thus synchronized over time, at least concerning critical data. This paper elaborates on the problem of performance, related to the discovery and maintenance of such overlay networks in a mobile ad hoc context. We analyze SLOT, an overlay selected based on a Relative Neighbour Graph (RNG) scheme. We then apply SLOT to a standard IP protocol: OSPF, a popular routing protocol which has recently been extended, with RFC 5449 and RFC 5614, to work also on mobile ad hoc networks, and which makes use of a similar overlay synchronization subgraph. This paper compares the performance of these existing OSPF mechanisms with that of SLOT-OSPF, a novel OSPF extension for mobile ad hoc networks using SLOT. Simulations show that SLOT-OSPF produces drastically less control traffic than RFC 5449 or RFC 5614, allowing SLOT-OSPF to function correctly while the other existing approaches stall, when the number of routers in the domain is large