Introduction

“P2P” or “peer-to-peer networking” is maybe one of the most controversial and interesting trends in the dawn of the new century; its complete decentralization challenges all definitions of private intellectual property and creates new technological, commercial and juridic challenges.

In this article I will enumerate some companies that provide P2P file-sharing services, after providing a short overview of the concept and implementation of P2P.

Technology

In a few words, the term peer-to-peer

“refers to the concept that in a network of equals (peers) using appropriate information and communication systems, two or more individuals are able to spontaneously collaborate without necessarily needing central coordination”

(Schoder & Fischbach, 2006).

In this broad category not only enter the well-known (and hated, see “The Register” reference below) file sharing networks, some of which will be enumerated later; but also applications old as the Internet itself, such as the Usenet or FidoNet, which can also be called P2P networks (Wikipedia, 2006).

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TCP congestion control tries to bring solutions to the problem of packet loss, which happens in networks for several reasons:

1. Increasing number of hosts connected to the network;
2. Increased traffic to and from the hosts;
3. Limited capacity of routers in between hosts and networks (Kurose & Ross, page 254).

Congestion is an important problem raised by multimedia streaming applications, where a high quantity of UDP packets (typically with audio and video information) is sent through the network with important rates. The problem with this approach is that UDP has no congestion traffic, and as such packets might be dropped by routers if a buffer overflow occurs. TCP, on the other hand, provides network congestion management, but

“TCP is not well-suited for many applications such as streaming multimedia, because TCP congestion control algorithms introduce large variations in the congestion window size (and corresponding large variations in the sending rate)”

(Kyasanur)

Network congestion, in turn, has complex consequences in terms of lower perceived quality of service, which is easily seen by the low quality of IP telephony communications in peak hours, bad quality video connections, and the commercial implications of these problems (difficulty to newcomers to provide innovative services, low acceptance by end users, etc). Continue reading →