Implementation of a unified userspace time handling library under the Linux OS

An appropriate assessment of end-to-end network performance presumes highly efficient time tracking and measurement with precise time control of the stopping and resuming of program operation. In this paper, a novel approach to solving the problems of highly efficient and precise time measurements on PC-platforms and on ARM-architectures is proposed. A new unified High Performance Timer and a corresponding software library offer a unified interface to the known time counters and automatically identify the fastest and most reliable time source, available in the user space of a computing system. The research is focused on developing an approach of unified time acquisition from the PC hardware and accordingly substituting the common way of getting the time value through Linux system calls. The presented approach provides a much faster means of obtaining the time values with a nanosecond precision than by using conventional means. Moreover, it is capable of handling the sequential time value, precise sleep functions and process resuming. This ability means the reduction of wasting computer resources during the execution of a sleeping process from 100% (busy-wait) to 1-1.5%, whereas the benefits of very accurate process resuming times on long waits are maintained.

Untersuchung der Auswirkung der MAC-Zugriffsverfahren im IEEE 802.11 auf die L4-Performance in mobilen IP-Netzen

Gegenstand der hier vorliegenden Arbeit ist die Untersuchung der Auswirkung der MAC-Zugriffsverfahren CSMA/CA auf das Transportschicht-Protokoll in WLAN-Netzen. Zum Erreichen des Ziels dieser Arbeit wurde es zuerst nachgewiesen, dass CSMA/CA zum TCP-Retransmission führen könnte. Dann die kumulative Verteilung der OWDs auf jedem Szena-rio analysiert. Am Ende wurde die kumulative Verteilung der Abstände zwischen den Spitzenwerten der OWD nach der Datenverarbeitung auf jedem Szenario analysiert.

Improving TCP Performance on CSMA/CA Connections

In IP networks, most of packets, that have been dropped, are recovered after the expiration of retransmission timeouts. These can result in unnecessary retransmissions and needless reduction of congestion window. An inappropriate retransmission timeout has a huge impact on TCP performance. In this paper we have proved that CSMA/CA mechanism can cause TCP retransmissions due to CSMA/CA effects. For this we have observed three wireless connections that use CSMA/CA: with good link quality, poor link quality and in presence of cross traffic. The measurements have been performed using real devices. Through tracking of each transmitted packet it is possible to analyze the relation between one-way delay and packet loss probability and the cumulative distribution of distances between peaks of OWDs. The distribution of OWDs and the distances between peaks of OWDs are the most important parameters of tuning TCP retransmission timeout on CSMA/CA networks. A new perspective through investigating the dynamical relation between one-way delay and packet loss ratio depending on the link quality to enhance the TCP performance has been provided.

A Model of Video Traffic Transmission in IP Networks

Telecommunications and network technology is now the driving force that ensures continued progress of world civilization. Design of new and expansion of existing network infrastructures requires improving the quality of service(QoS). Modeling probabilistic and time characteristics of telecommunication systems is an integral part of modern algorithms of administration of quality of service. At present, for the assessment of quality parameters except simulation models analytical models in the form of systems and queuing networks are widely used. Because of the limited mathematical tools of models of these classes the corresponding parameter estimation of parameters of quality of service are inadequate by definition. Especially concerning the models of telecommunication systems with packet transmission of multimedia real-time traffic.

Comparison of Contemporary Protocols for High-speed Data Transport via 10 Gbps WAN Connections

This work is dedicated to comparison of open source as well as proprietary transport protocols for highspeed data transmission via IP networks. The contemporary common TCP needs significant improvement since it was developed as general-purpose transport protocol and firstly introduced four decades ago. In nowadays networks, TCP fits not all communication needs that society has. Caused of it another transport protocols have been developed and successfully used for e.g. Big Data movement. In scope of this research the following protocols have been investigated for its efficiency on 10Gbps links: UDT, RBUDP, MTP and RWTP. The protocols were tested under different impairments such as Round Trip Time up to 400 ms and packet losses up to 2%. Investigated parameters are the data rate under different conditions of the network, the CPU load by sender andreceiver during the experiments, size of feedback data, CPU usage per Gbps and the amount of feedback data per GiByte of effectively transmitted data. The best performance and fair resources consumption was observed by RWTP. From the opensource projects, the best behavior is showed by RBUDP.

The Research of Increase of Channel Efficiency for IP Traffic Transmission over Digital Power Line Carrier Channels

This article is devoted to the research of channel efficiency for IP-traffic transmission over Digital Power Line Carrier channels. The application of serial WAN connections and header compression as methods to increase channel efficiency is considered. According to the results of the research an effective solution for network traffic transmission in DPLC networks was proposed.

Analitzador del tràfic de Xarxa per entorn Linux 'Sniff All'

L'objectiu d'aquest treball de final de carrera és clar pel que fa a la funcionalitat: es tracta de fer un analitzador de xarxa (vulgarment conegut com a detector) que funcioni en entorns Linux i amb interfícies d'usuari gràfiques.

Localitzador Gràfic d' Adreces IP

Aquest projecte estudia el problema de l'extracció i la visualització de manera entenedora de la informació pública més rellevant d'una adreça IP, tot i que no aborda els problemes relacionats amb la informació insuficient perquè pertanyen a un àmbit de recerca diferent.

Estadítiques de crides al sistema en plataforma GNU/Linux

Aquest projecte es basa en la modificació del kernel (nucli) del sistema operatiu GNU/Linux per dotar-lo de la capacitat d'extreure estadístiques de les crides al sistema (syscalls). A partir de la compilació i instal·lació d'un nou nucli es registra la informació del nombre de vegades i la freqüència amb què es fan aquestes crides al sistema, i posteriorment es representa en un informe d'estadístiques explicatives.

Proyecto de migración a un sistema de telefonia IP (VOIP) basado en software libre.

Una empresa de grandària mitja s'embarca en un projecte de migració del seu sistema telefònic, basat en un model tradicional i amb múltiples problemes, tant a nivell de funcionalitat com de costos, i decideix apostar per una solució basada en programari lliure, amb Linux i Asterisk com peces angulars del disseny del projecte.

Enhancing MPLS QoS routing algorithms by using the network protection degree paradigm

IP based networks still do not have the required degree of reliability required by new multimedia services, achieving such reliability will be crucial in the success or failure of the new Internet generation. Most of existing schemes for QoS routing do not take into consideration parameters concerning the quality of the protection, such as packet loss or restoration time. In this paper, we define a new paradigm to develop new protection strategies for building reliable MPLS networks, based on what we have called the network protection degree (NPD). This NPD consists of an a priori evaluation, the failure sensibility degree (FSD), which provides the failure probability and an a posteriori evaluation, the failure impact degree (FID), to determine the impact on the network in case of failure. Having mathematical formulated these components, we point out the most relevant components. Experimental results demonstrate the benefits of the utilization of the NPD, when used to enhance some current QoS routing algorithms to offer a certain degree of protection

IpViSix : Distribución LiveCD GNU/Linux con herramientas IPv6

Este documento describe qué contiene IpViSix, cómo se ha construido y para qué puede ser útil esta distribución de GNU/Linux que incorpora una serie de herramientas basadas en software libre que permiten tanto probar aplicaciones y redes como implementar servicios de red básicos.

Disseny i implementació d'un algorisme predictiu de coscheduling dins l'espai d'usuari en un cluster Linux

Dissenyar i implementar un planificador en l'espai d'usuari basant-se en la tècnica de coscheduling, en concret s'utilitzarà coscheduling predictive. L'objectiu és intentar obtenir un rendiment similar al que es va assolir en implementacions de la mateixa tècnica realitzada en l'espai de kernel.

Time Series Input Selection using Multiple Kernel Learning

In this paper we study the relevance of multiple kernel learning (MKL) for the automatic selection of time series inputs. Recently, MKL has gained great attention in the machine learning community due to its flexibility in modelling complex patterns and performing feature selection. In general, MKL constructs the kernel as a weighted linear combination of basis kernels, exploiting different sources of information. An efficient algorithm wrapping a Support Vector Regression model for optimizing the MKL weights, named SimpleMKL, is used for the analysis. In this sense, MKL performs feature selection by discarding inputs/kernels with low or null weights. The approach proposed is tested with simulated linear and nonlinear time series (AutoRegressive, Henon and Lorenz series).

Implantació de la telefonia IP en un entorn empresarial

L’objectiu d’aquest treball és dissenyar un model general d’un sistema de telefonia IP per a una petita o mitjana empresa. El model ha de tenir en compteles característiques actuals de la xarxa de l’empresa i proposar una solució adient. Un altre requeriment és la utilització de software de lliure distribució, des del sistema operatiu fins al relatiu a VoIP, i més concretament, el software de centraleta VoIP Asterisk sobre GNU/Linux.En primer lloc s’estudiaran els conceptes bàsics de la telefonia IP (protocols,codificadors, servidors, etc.). En segon lloc, s’analitzaran els diferents escenarispossibles i es proposaran solucions adequades per cadascun d’ells. Després s’estudiarà el funcionament de les centraletes Asterisk i la seva configuració encada escenari. Finalment s’aplicarà aquest estudi a una empresa concreta