[bittorrent] Piece download strategy

chris erway cce at cs.brown.edu
Thu Apr 23 14:47:09 EDT 2009


Following up what Nikitas said, there are quite a few BitTorrent  
streaming papers:
   http://scholar.google.com/scholar?&q=video%20streaming%20bittorrent

For the last couple of years, BT streaming has been one of the  
suggested project ideas for the P2P networking seminar course that my  
advisor teaches here.  It's not too hard to get a naive strategy  
working; even easier for heavily-seeded torrents & low-bitrate files.

Libtorrent has "sequential download support"; one of our seminar  
groups once worked on tweaking its strategy to mix rarest-first with  
sequential.
   http://www.rasterbar.com/products/libtorrent/manual.html#set-sequential-download-is-sequential-download

I agree there isn't really a good production client out there that  
does this.  Except for Bitlet, which plays torrents of MP3s via a Java  
applet in your browser -- I imagine they're probably doing sequential  
downloading:
   http://www.bitlet.org/music

Hope these links help!

chris

On Apr 23, 2009, at 7:07 AM, Nikitas Liogkas wrote:

> I recall there have been some papers discussing this as part of a  
> bigger
> system (usually having to do with video streaming), but I don't  
> remember
> the titles off the top of my head. You can look for them at P2P
> conferences, such as IPTPS.
>
> HTH
> nikitas
>
> Rayson Ho wrote:
>> (I've read the FAQ, and watched Bram's talk online [1])
>>
>> I know that the download strategy used by BT is usually rarest first.
>> However, this means that there usually are many "holes" in a file  
>> when
>> downloading.
>>
>> It's not a problem if the torrent is well seeded. However if the
>> availability of seeds is not stable, or if there is only 1 seed, then
>> I think using the sequential order can give the user quite a lot of
>> benefits -- if it is a music or movie file, then the user can at  
>> least
>> view the beginning of it, and if it is a source tarball, then at  
>> least
>> some part of the directory can be extracted...
>>
>> Any one has worked on this before?? I am not replacing the rarest
>> first strategy, but if the availability is same, then I want to bias
>> towards sequential order (or even biggest consecutive piece first --
>> try to construction a bigger piece).
>>
>> Thanks,
>> Rayson
>>
>> [1]:
>> http://www.stanford.edu/class/ee380/Abstracts/050216.html
>> http://stanford-online.stanford.edu/courses/ee380/050216- 
>> ee380-100.asx
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