[opendtv] Re: 5th gen receivers
- From: Kon Wilms <kon@xxxxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Sat, 22 Jan 2005 11:41:14 -0800
On Sat, 2005-01-22 at 14:17 -0500, Tom Barry wrote:
> Kon Wilms wrote:
>
> > P2P is unicast. Quite the contradiction there.
>
> Why must someone have only one peer? What do you call getting a file
> from BitTorrent where it comes from multiple P2P sources?
Even though it is coming from multiple sources, each connection to
retrieve and deliver a piece of the file is a one-to-one connection.
> Is there some reason that P2P nodes could not use multi-cast in
> conjunction with, say, anonymous DC-Nets (Herbivore)? It would seem
> some algorithms like that might gain something by sharing info with more
> than one peer at a time. But that is not my area, so I may well be
> overlooking something.
Multicast UDP isn't practical since routers block it - and - the P2P
networks' delivery model goes against everything that is multicast (i.e.
a continuous unreliable packet stream to multiple unknown (or knowlingly
pruned) hosts). With P2P the file and its integrity is the network, with
streaming multicast the packet stream and bitrate is the network.
IMHO The best way to create a P2P video delivery system would be to seed
and pad the entire file as it is done now, but change the algorithm so
that it attempts to collect packets linearly from the start of the file
(vs. collections of packets anywhere in the file). That in effect
changes the model from one of 'the more people download the faster the
file arrives' to 'the more people download the longer the play buffer'.
Ofcourse FF capability would be exponential, but RW and Pause shouldn't
be a problem. I've seen efforts to introduce FEC to P2P algorithms -
that would further help the system work if the file bitrate is slightly
below the watermark or there are not enough super/nodes feeding the
network.
Imagine the sheer delivery power of a (fairly) high-bitrate fec datacast
(where packet groups are randomized and carouseled) combined with a
backchannel using P2P swarmed delivery. :-) You could seed the buffer
with the forward channel and fill the file in with the P2P network.
Cheers
Kon
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