Usenet NEWS vs. Bittorrent

[Leo Mauler]

--- On Sun, 7/6/08, Jeffrey Watts <jeffrey.w.watts at gmail.com> wrote:

> On Sat, Jul 5, 2008 at 4:41 AM, Leo Mauler
> <webgiant at yahoo.com> wrote:
> 
> > Bittorrent suffers from the requirement that someone
> > with 100% of the original file has to sit there for 
> > days uploading the file if someone else doesn't have 
> > all the bittorrent parts.
> 
> Well, that's really not how it works.  If there's 1
> seed and 10 peers, all of those peers will eventually 
> become seeds, so that situation really isn't that 
> common.

Yes, if there's one seed and 10 peers, that one seed with 100% of the original file has to sit there for days uploading the file until someone else (i.e., the other 10 peers) become seeds (i.e., become someone else who has all the bittorrent parts).

All you did was restate what I said, using slightly different wording, and then claimed it meant something else.  The aforementioned situation is entirely too common prior to the *swarm* receiving 100% of the seeder's uploaded file(s), a situation which can take days to change into "all seeders".

> Also, those peers are sharing what _they have_ with 
> other peers as well, so the seed doesn't really have 
> to share all of what it has.

The seed has to seed itself out to 100% before the *swarm* gets a complete set of parts, so the seeder really does need to spend days sharing out *all* of what it has.  By definition all the peers start off at 0%, so the seeder has to seed out 100% to the swarm before 100% of the file is available to everyone in the swarm.

You might as well argue that a person can create a new book that no one else has, then only give out 80% to everyone else, and yet everyone somehow manages to get 100% of the book they didn't have to begin with, using only 80% of the original book.

> In practice it works very well.

In theory it works well.  In practice it doesn't work very well, because everyone isn't using the basic Bittorrent client.

For example, some bittorrent clients permit individual torrent upload bandwidth throttling.  This allows a peer to download the entire file but share very little, putting more of an uploading burden on the original seeder.  

Also, bittorrent clients which permit encryption have the option of only allowing connections from other encrypted clients.  If the seeder allows for both types of connections, the seeder is the sole seeder for a peer which refuses unencrypted connections.
 
Bittorrent is completely reliant on polite sharing.  If the peer, upon reaching 100%, performs a "hit-and-run" maneuver and disconnects from the swarm, the peer does not become a seeder and all of his or her parts vanish from the swarm.  If this means that the only person left with 100% is the seeder, the seeder must continue seeding even longer.

To contrast with Usenet NEWS binary groups, the uploader uploads once, to one location, with PAR2 files for additional security.  Thereafter the parts are available for usually a week or longer and downloadable at much faster speeds than bittorrent.