Faster end game

From EMule Wiki
(Difference between revisions)
Jump to: navigation, search
m
(Undo revision 3005 by Izegiwera (Talk))
 
(7 intermediate revisions by 5 users not shown)
Line 1: Line 1:
−
Faster Endgame aka ''Dynamic Block Requests'' is a technique which shall speed up the file completion.
+
Faster Endgame AKA ''Dynamic Block Requests'' is a technique employed for faster file completion.
  
  
−
== Netfinitys Dynamic Block Requests ==
+
== Netfinity's Dynamic Block Requests ==
  
−
Faster endgame by not requesting many blocks if the downloading file is near completion. A requested data range is blocked for downloading, you cannot download a certain datarange from multiple clients (by design of emule, the protocol would allows this). So by requesting less blocks from slower clients we can request more blocks from faster uploading clients which results in a speedup and faster file completion.
+
Faster endgame by not requesting many blocks if the downloading file is near completion.  
  
−
This feature only makes sense if only a small size of a file is left to download.
+
Downloading procedure goes as follows:
 +
*Connection to a peer is made and it is determined what [[chunk]]s the peer has.
 +
*A Data range on the local client is reserved for downloading. This a small part of the file. That same data range will not be requested from other peers.
 +
*That data range is then requested from the peer.  
  
−
An earlier implementation included "dropping" of too slow sources 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)
+
So, by requesting fewer blocks from slower peers we can request more/bigger blocks from faster peers, 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.
  
−
== Dazzles Faster Endgame ==
+
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 after a while (e.g. if you're on a trickle slot).
  
−
Another implementation is "Dazzles 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.
+
=== Netfinity's Explanation ===
 +
'''Phase 1: Block request sizes'''
  
 +
*1. Estimate the time to completion.
 +
time_to_complete = bytes_left_to_download / datarate_all_sources
 +
 +
*2. Estimate the number of bytes to request so that source doesn't complete later than 10 seconds after the estimated file completion.
 +
bytes_to_request = source_datarate / (time_to_complete + 10)
 +
 +
*3. Split the request in three to fill the OP_PARTREQ, but round numbers to nearest  10kB.
 +
 +
'''Phase 2: Put the source on hold if it can't request enought bytes, without breaking the completion estimate'''
 +
 +
This means that if calculation in phase 1 returned less than 10kB then the source is put on hold for 20 seconds, then it's dropped if no new blocks becomes available. Note this is only done when the source has sent all the pieces we requested. This is done in case the other sources fails or the part is corrupt, then we can recontinue download with this source.
 +
 +
'''Phase 3: Dropping slow sources'''
 +
 +
This phase is only entered if a fast source can't allocate any more blocks. Here we drop in the middle of a transaction, thus data will be lost.
 +
 +
*1. Find the slowest source that is slower than 1kB/s and would break the completion estimate.
 +
The calculations is basicaly the same as in phase 1.
 +
 +
*2. Cancel the download and free all allocated blocks
 +
This causes data loss (upto ~20kB), as there is likely to be incomplete packets transfer. You have to take much care when doing this!
 +
 +
 +
NOTE! My actual algorithm is much more complex, but this is the primary basics. Also, I always keep my request within the 180kB AICH block bounds in hope to handle curruption better.
 +
 +
/netfinity
 +
 +
This text has taken from http://forum.emule-project.net/index.php?showtopic=92937&view=findpost&p=662988
 +
 +
== Dazzle's Faster Endgame ==
 +
 +
Another implementation is "Dazzle's faster endgame" 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 peer 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.
 +
 +
How is this bad? The source could be used for A4AF. What else? --[[User:134.130.183.101|134.130.183.101]] 05:07, 22 August 2008 (CEST)
  
 
== Morph Approach ==
 
== Morph Approach ==
  
 
TODO:
 
TODO:
−
I've seen that Morph includes an own version of DBR, though I hadn't have any time to check it in detail... if anyone knows more, please add it --WiZaRd 21:34, 15 Jun 2006 (CEST)
+
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 ==
 
== Official Approach ==
  
−
The official client partially adapted Netfinitys feature by introducing 2 new features:
+
The official client partially adapted Netfinity's feature by introducing two new features:
  
−
* if a file is near completion and downloadspeed of a source is pretty low then less block requests will be created
+
* if a file is near completion and the download speed of a source is pretty low then fewer block requests will be created for that client.
−
* block requests are shrunk now to avoid "already requested ranges"  
+
* block requests are reduced in size to avoid "already requested ranges".
  
  
 
== Conclusion ==
 
== Conclusion ==
  
−
Netfinitys 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 Dazzles version
+
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.
  
 
[[category:features]]
 
[[category:features]]

Latest revision as of 09:06, 24 November 2010

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


Contents

[edit] 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 reserved for downloading. This a small part of the file. That same data range will not be requested from other peers.
  • That data range is then requested from the peer.

So, by requesting fewer blocks from slower peers we can request more/bigger blocks from faster peers, 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 after a while (e.g. if you're on a trickle slot).

[edit] Netfinity's Explanation

Phase 1: Block request sizes

  • 1. Estimate the time to completion.

time_to_complete = bytes_left_to_download / datarate_all_sources

  • 2. Estimate the number of bytes to request so that source doesn't complete later than 10 seconds after the estimated file completion.

bytes_to_request = source_datarate / (time_to_complete + 10)

  • 3. Split the request in three to fill the OP_PARTREQ, but round numbers to nearest 10kB.

Phase 2: Put the source on hold if it can't request enought bytes, without breaking the completion estimate

This means that if calculation in phase 1 returned less than 10kB then the source is put on hold for 20 seconds, then it's dropped if no new blocks becomes available. Note this is only done when the source has sent all the pieces we requested. This is done in case the other sources fails or the part is corrupt, then we can recontinue download with this source.

Phase 3: Dropping slow sources

This phase is only entered if a fast source can't allocate any more blocks. Here we drop in the middle of a transaction, thus data will be lost.

  • 1. Find the slowest source that is slower than 1kB/s and would break the completion estimate.

The calculations is basicaly the same as in phase 1.

  • 2. Cancel the download and free all allocated blocks

This causes data loss (upto ~20kB), as there is likely to be incomplete packets transfer. You have to take much care when doing this!


NOTE! My actual algorithm is much more complex, but this is the primary basics. Also, I always keep my request within the 180kB AICH block bounds in hope to handle curruption better.

/netfinity

This text has taken from http://forum.emule-project.net/index.php?showtopic=92937&view=findpost&p=662988

[edit] Dazzle's Faster Endgame

Another implementation is "Dazzle's faster endgame" 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 peer 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.

How is this bad? The source could be used for A4AF. What else? --134.130.183.101 05:07, 22 August 2008 (CEST)

[edit] 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)


[edit] Official Approach

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

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


[edit] 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.

Retrieved from "?title=Faster_end_game&oldid=3017"
Personal tools