Port (computer networking)

Abstract: In combination with a wheel for a bicycle and the like having an annular rim, a hub rotatable about its axis, and axially offset groups of circumferentially spaced spokes which centrally support the hub on the rim; a wheel decorating ornament comprising an annular, planar sheet of material decorated on opposite sides, axially disposed between the groups of spokes and radially disposed between the rim and the hub.

Abstract: Well-known port numbers can no longer be used to reliably identify network applications. There is a variety of new Internet applications that either do not use well-known port numbers or use other protocols, such as HTTP, as wrappers in order to go through firewalls without being blocked. One consequence of this is that a simple inspection of the port numbers used by flows may lead to the inaccurate classification of network traffic. In this work, we look at these inaccuracies in detail. Using a full payload packet trace collected from an Internet site we attempt to identify the types of errors that may result from port-based classification and quantify them for the specific trace under study. To address this question we devise a classification methodology that relies on the full packet payload. We describe the building blocks of this methodology and elaborate on the complications that arise in that context. A classification technique approaching 100% accuracy proves to be a labor-intensive process that needs to test flow-characteristics against multiple classification criteria in order to gain sufficient confidence in the nature of the causal application. Nevertheless, the benefits gained from a content-based classification approach are evident. We are capable of accurately classifying what would be otherwise classified as unknown as well as identifying traffic flows that could otherwise be classified incorrectly. Our work opens up multiple research issues that we intend to address in future work.

Abstract: Recent literature has emphasized the importance of transport costs and infrastructure in explaining trade, access to markets, and increases in per capita income. For most Latin American countries, transport costs are a greater barrier to U.S. markets than import tariffs. We investigate the determinants of shipping costs to the U.S. with a large database of more than 300,000 observations per year on shipments of products aggregated at six-digit HS level from different ports around the world. Distance volumes and product characteristics matter. In addition, we find that ports efficiency is an important determinant of shipping costs. Improving port efficiency from the 25th to the 75th percentile reduces shipping costs by 12 percent. (Bad ports are equivalent to being 60% farther away from markets for the average country.) Inefficient ports also increase handling costs, which are one of the components of shipping costs. Reductions in country inefficiencies associated to transport costs from the 25th to 75th percentiles imply an increase in bilateral trade of around 25 percent. Finally, we try to explain variations in port efficiency and find that they are linked to excessive regulation, the prevalence of organized crime, and the general condition of the country's infrastructure.

Abstract: This paper argues that, with the rapid and pervasive restructuring of supply chains and of the logistics pathways in which ports are embedded, existing paradigms no longer offer adequate insights into the functions of ports or port authorities. Rather, ports must now be seen as elements in value-driven chain systems or in value chain constellations. They deliver value to shippers and to third party service providers; customer segmentation and targeting is on the basis of a clearly specified value proposition; and the port captures value for itself and for the chain in which it is embedded. The role of ports and port authorities, and the way in which they position themselves in the new business environments beyond 2001 must be defined within a paradigm of ports as elements in value-driven chain systems, not simply as places with particular, if complex, functions.