Faster end game

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Faster Endgame AKA Dynamic Block Requests is a technique employed for faster file completion.


Contents

Netfinity's Dynamic Block Requests

Faster endgame by not requesting many blocks if the downloading file is near completion.

Downloading procedure goes as follows:

  • Connection to a peer is made and it is determined what chunks the peer has.
  • A Data range on the local client is reserverved for downloading. This a small part of the file. That same datarange will not be requested from other peers.
  • That same datarage is request from the peer.

So by requesting less blocks from slower clients we can request more/bigger blocks from faster uploading clients which results in a speed increase and faster file completion.

This feature only makes sense if a small part of a downloading file//chunk remains.

An earlier implementation included "dropping" of sources that are too slow in order to allow faster clients to take over. Dropping sources is not always a good idea since sources that are slow now might become fast sources in a while (e.g. if you're on a trickle slot).

Dazzle's Faster Endgame

Another implementation is "Dazzle's faster endgame" feature which simply drops the slowest source from a file if no more block requests can be created. This is bad because block requesting might also fail if a client simply has no more blocks for us (No Needed Part Source), thus dropping a source would be very bad in such a situation and won't help at all.


Morph Approach

TODO: I've seen that Morph includes an own version of DBR, though I have not had any time to check it in detail... if anyone knows more, please add it --WiZaRd 21:34, 15 Jun 2006 (CEST)


Official Approach

The official client partially adapted Netfinity's feature by introducing 2 new features:

  • if a file is near completion and the download speed of a source is pretty low then less block requests will be created for that client.
  • block requests are reduced in size to avoid "already requested ranges".


Conclusion

Netfinity's original implementation is by far superior to any present implementation as it combines better dynamic block requests than the version in ESE mod plus better/more intelligent slow source dropping than Dazzle's version.

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