Metrologia de redes: estimativa da capacidade do caminho em uma rede embutido no protocolo TCP

Abstract

The Metrics Network is to measure the network performance and the difficulty increases with the growth of these as the Internet. Certain applications on the Internet would work best if they could obtain characteristics of trodden paths. There are a number of research techniques that aim to measure these characteristics. As an example, we can estimate the capacity of the path in a network, estimate the available bandwidth, identify the best ways considering the load balancing and measuring the performance of a path with respect to loss, oneway delay, the RTT (Round Trip Time) and jitter. Are determining factors in obtaining metrology characteristics of networks, and take no help from the network equipment that are on the way, use the least traffic and further processing, ie, low cost, and above all, keep timeliness of the features, enough for one application can use the results. This work reproduces and compares the main solutions that enable the estimation of capacity of a path using the Transmission Control Protocol (TCP). We used the technique created by the group of measurements of the Federal University of Espirito Santo, TCP-ECAP (Embedded Path Capacity Estimator in TCP) used passively, without the use of search packages and the estimated capacity is obtained by performing inferences in the protocol TCP respecting the minimum number of changes from the method of obtaining the estimate of capacity per pair of packets. There have been changes in the application files in Linux TCP resulting in the need to compile a Kernel. The data network of the Brazilian Army was used for the experiments of the tool, with the selection of Web servers located in Brasilia, São Paulo, Porto Alegre and Rio de Janeiro. Tests were conducted with a graphics generator called Pathcrawler in order to visually enhance the results.