What extensions are important/mandatory for a modern bittorrent client?

[feross]

The bittorrent extension protocol (BEP10) allows clients to innovate and come up with their own extensions to the protocol. A few extensions, like torrent metadata (BEP9), DHT (BEP5), and the PORT message are widely supported. WebTorrent already has basic support for these.

However, there are probably other extensions that are de facto mandatory in modern clients. Once nearly all clients support a feature, I'd guess that clients without the feature are at risk of being ignored, or at a speed disadvantage. Which extensions fit this description?

If you're familiar with bittorrent, please feel free to chime in. I'd love more help from people who know about bittorrent!

[feross]

Looking at what other clients support, I think we should support:

• encryption
• peer exchange protocol (PEX)
• µTP
• UPnP and NAT-PMP port forwarding
• webseed support

[gauravsaini]

By encryption you mean the data encryption , if yes then it will be great.

I think anonymising the user is heavily required looking at how the snooping is being done everywhere.
I'm really looking forward to an elegant way of hiding the user identity , which I think nobody has provided in the torrent client till now .

[feross]

Yes, I'm referring to BitTorrent protocol encryption. Anonymizing the user is another issue completely, and much harder.

[gauravsaini]

And then I thought people at Stanford can do anything..Must be harder..;)

[cagedwisdom]

Mutable torrent support would be really good. Here's a BEP39, although I'd prefer an implementation that let torrent clients push a new torrent file iff it's an updated version.

[transitive-bullshit]

I added individual issues tracking each of these extensions.

• PEX Implement PEX extension #65
• Web (HTTP) seeding Implement Web (HTTP) Seeding (BEP17+BEP19) #67
• µTP Implement µTP extension (BEP29) #68
• Encryption (PE/MSE) Implement Protocol Encryption (PE/MSE) #69

Note that I couldn't find any substantive background info on bittorrent UPnP, so I left that one off for now. @feross I think this issue should be closed as answered and further progress should be tracked in these sub issues.