Biblio

Traffic normalization, i.e. enforcing a constant stream of fixed-length packets, is a well-known measure to completely prevent attacks based on traffic analysis. In simple configurations, the enforced traffic rate can be statically configured by a human operator, but in large virtual private networks (VPNs) the traffic pattern of many connections may need to be adjusted whenever the overlay topology or the transport capacity of the underlying infrastructure changes. We propose a rate-based congestion control mechanism for automatic adjustment of traffic patterns that does not leak any information about the actual communication. Overly strong rate throttling in response to packet loss is avoided, as the control mechanism does not change the sending rate immediately when a packet loss was detected. Instead, an estimate of the current packet loss rate is obtained and the sending rate is adjusted proportionally. We evaluate our control scheme based on a measurement study in a local network testbed. The results indicate that the proposed approach avoids network congestion, enables protected TCP flows to achieve an increased goodput, and yet ensures appropriate traffic flow confidentiality.

Food safety policies have aim to promote and develop feeding and nutrition in society. This paper presents a system dynamics model that studies the dynamic behavior between transport infrastructure and the food supply chain in the city of Bogotá. The results show that an adequate transport infrastructure is more effective to improve the service to the customer in the food supply chain. The system dynamics model allows analyze the behavior of transport infrastructure and supply chains of fruits and vegetables, groceries, meat and dairy. The study has gone some way towards enhancing our understanding of food security impact, food supply chain and transport infrastructure.