>Oh, and aren't newsgroups more or less peer-to-peer messaging using a >more efficient model than regular P2P? It's like P2P with a local ISP >cache.
Sorta, kinda? USENet is actually pretty bandwidth inefficient beast. "Your" server is peered with any number of other servers. Periodically your server asks all its peers "got anything new?" - if so they send everything. At the same time they're asking your server the same question - when you post a message it gets added to your server and then propagates from peer to peer (this process might take a significant amount of time) until "everybody" has it. In specific however each peer may choose to accept "everything", only some groups or only certain messages (just new ones, or ones younger than a certain age for example). In the end however if you've got a network of a million peers then you've got a million copies of the message. Since the servers have vastly different speed and storage profiles you get huge diffences in "retention" - a huge server might be able to store a year's worth of data while an average server only a month and a tiny server only a day or two. Compared to peer-to-peer which leaves the actual data on the "home" servers until requested and, until then, just sends metadata USENet isn't as resource friendly. Even a large binary message is shared amongst ALL peers even if NOBODY ever requests it - if it's posted, it's transfered (again and again and again). USENet was also not designed for binary transfers (although they make up the vast bulk of the bandwidth used) and need to convert any binary files to text - this often expands the files making them bigger in transmission than in the native format. Because of the uncertainty of USEnet (retention rate, peerage, etc) most groups have adopted procedures for ensuring quality transfers. One of these is provide PAR (parity) files for large binaries. Using these files any corrupted or missing message parts can be rebuilt (as far as I'm concerned it's witchcraft pure and simple). The trouble is a full "PAR set" needs to be, usually, about 20% of the file size. It's also generally accepted practice to include a sample of any media files. So a 700 Meg movie downloaded from peer-to-peer would be 700 meg. A 700 Meg movie on USENet is 750 meg converted to text, plus, say 160 meg of PAR files plus maybe a 30 meg sample file. And, again - these are all copied to every peer regardless of demand. A 700 Meg movie on a peer-to-peer network that nobody ever requests uses essentially zero bandwidth. USENet is also limited geographically: you connect to whatever server you connect to. A closer server (even a peer) might be faster, but you don't have access. Peer-to-peer attempts to optimize the connection by downloading files from the closest/fastest peer that hosts them and downloading using multiple hosts. Once you have the file you also become a new node, a new host, for that file thus allowing the system to optimize even further. Once I download something from USENet it's mine and nobody else can see it. In short USENet servers act a lot like a peer-to-peer network where everybody is constantly requesting every file from everybody else. For the end user USENet is more like the Web - a provider and a consumer with a very large downstream and very small upstream data flows. This is simplistic of course - there are all sorts of tricks. On-the-wire compression helps text-only USEnet more than peer-to-peer and much of USENet traffic is still run over the relatively open backbone connections - it's the last mile connections that are truly getting clogged and these are exactly what's leveraged most by peer-to-peer. But in the end I'm still a little suprised that USENet doesn't have a stronger showing. Jim Davis ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~| Adobe® ColdFusion® 8 software 8 is the most important and dramatic release to date Get the Free Trial http://ad.doubleclick.net/clk;203748912;27390454;j Archive: http://www.houseoffusion.com/groups/CF-Community/message.cfm/messageid:262625 Subscription: http://www.houseoffusion.com/groups/CF-Community/subscribe.cfm Unsubscribe: http://www.houseoffusion.com/cf_lists/unsubscribe.cfm?user=89.70.5
