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Hybrid and v2 Torrents

Quick version:

Please create v1 only torrents.
Uploads of hybrid and/or v2 torrents can cause issues with legacy clients and tracker.

Detailed version:

As the BitTorrent protocol matured over time there have been new features and implementation details added to it. One of the more recent additions is the specification of a new .torrent file format to address some issues with the previous specification.

You can read more about the technical details here at libtorrent's (rasterbar) blog. Libtorrent (rasterbar) is a popular implementation of the BitTorrent protocol, used in such clients as qBittorrent, so it is expected that these changes will propagate to other clients as well. For the time being, however, qBittorrent 4.4.0 has become an early adopter of these changes.

What this means in practical terms is that there are now three types of .torrent files in circulation:

v1 or old format,
v2 or new format,
hybrid, which contains sufficient information for both v1 and v2 to work.

AsianCinema being in the Private Tracker "business" means we will have to make some decisions at this point regarding how we want to react to these changes. Superficially, it seemed to us that hybrid format torrents would be ideal because they allow a way forward while keeping backward compatibility. Unfortunately, it has come to our attention that not all is well on the hybrid front. Not to mention, the benefits of BitTorrent v2 for private trackers are marginal to non-existent. It is in public and open trackers, and the distribution of trackerless torrents, that the new specification delivers most of its benefits.

Although hybrid torrents are expected to work in-place with all manners of BitTorrent client and tracker software, it turns out that older software raises some issues. As a side-effect of the changes enshrined in v2, v1 tracker frontends and clients will see a directory named .pad alongside the actual torrent contents. As long as a user is downloading or seeding a torrent they will need to keep this directory intact. What's more, we have learnt that Transmission, another relatively popular client, currently has problems reading hybrid torrent files at all.

While the issue with .pad directory is largely a cosmetic one, the problem of a range of software being unable to read the torrent files is more serious because it handicaps a significant number of users who are for some reason or another tied to these clients. We also understand that at least some of these software are "baked" into embedded devices which most likely will not see an update any time soon, or ever. As long as these older versions don't pose known security threats to the users or the swarm it would be ideal to keep the environment hospitable to this part of the user base as well.

Taking these issues into account, we have decided to make the following policy requests from our users:

If you use qBittorrent version 4.4 and above, or other software capable of creating v2 and/or hybrid .torrent files for the purpose of uploading to trackers, please consider the above issues and set your client software to generate v1 only .torrent files. Please double-check to make sure your setting has taken effect before uploading your torrent.
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