First among equals

 作者:风奁窕     |      日期:2019-03-07 07:09:02
By Will Knight New techniques are making the Gnutella file-sharing network flourish, but may be taking away the key benefits of pure peer-to-peer networking. The peak number of simultaneous Gnutella users reached more than 40,000 in May, according to a monitoring company called Clip2. This is 20 times more than could originally connect to the network. In peer-to-peer networking, each desktop computer both provides and receives information, i.e. it acts as both a server and a client. The approach was first made famous by the controversial music file sharing service, Napster. Napster’s system allows computers to serve and retrieve music files but it still relies on central servers to find the files. Gnutella was designed to create a more pure peer-to-peer network. The first version removed the need for Napster’s central servers by sending requests for files to every computer on the network. In practice, however, this overloaded the network when more than a few thousand users were connected. Ironically, Gnutella is now moving back to a system reminiscent of Napster. Recent refinements to Gnutella and related software reduce the burden on the network by stopping clients with slow connections acting as servers. Instead, proxy servers – called reflectors – host information for the slower clients and reduce the overall strain on the network. “There appears to be a hierarchical backbone emerging,” says Theodore Hong, a research student at Imperial College specialising in peer-to-peer technology. “The reflector takes this one stage further by positioning some clients off the network altogether.” These reflectors have improved the performance of the Gnutella system. However, the music industry mounted legal challenges to Napster on the basis that the central servers were allegedly promoting copyright infringements. Experts say this has taken away the technical benefit of a pure peer-to-peer system: network stability. “The main emphasis is avoiding centralisation to create robustness,” says Hong. “If you make all the clients equal, then if one falls down, it doesn’t really matter.” Hong is helping to develop a completely decentralised peer-to-peer technology called Freenet. This was devised to provide absolute privacy but could also hold the key to providing a truly scalable, decentralised file-sharing system. According to the creator of Freenet, Ian Clark, simulations show that the technology will scale to many millions of users without relying on any central authority for stability. “The reason Freenet is so scalable is that it searches intelligently,” he told New Scientist. “No matter how big it gets, searches won’t take significantly longer.” With Freenet,