Ask HN: Why is there no P2P streaming protocol like BitTorrent?

The protocol seems like an excellent idea, but #3365a3 on black for the website text is one of the worst designs for open-source project websites I've seen yet.

Off-topic but I'm impressed with how many potentially revolutionary projects get funding from NLNet.

Twitch streamers seem to be fine with the 10-60 second latency Twitch adds, depending on how bad their network is performing. Requirements will differ per industry but I don't think latency is a killer necessarily.

I don't think people are appreciating the nuance of what you're saying. Most of what you are saying isn't accurate for netflix style streaming, which would actually be more aptly called "video on demand", but is very applicable to "live streaming" in the sense of live sporting events or news broadcasts.

Video-on-demand is perfectly implementable on top of BitTorrent. As you say, there are some latency pitfalls you'll have to avoid, but that's nothing you can't hack yourself out of.

Livestreaming is a different beast. As you say, the problem with livestreaming is that everyone needs the same content at the same time. If I spend 200ms downloading the next 500ms worth of content, then there's nobody to share it with, they all spent the 200ms doing the same. BitTorrent relies on the time shift that is allowed between me downloading the content and you requesting it. If you request it before I've got it, well I can't fulfil that request, only the guy I intend to get it from can.

If you wanted to implement something like that, you would probably pick a tree of seeders where the protocol would pick a subset of trusted nodes that it would upload the content to before then allowing them to seed it, and the have them doing the same recursively.

That would obviously introduce a bunch of complexity and latency, and would very much not be BitTorrent anymore.

If everybody starts at the start then it will be very poorly seeded when everybody wants it, before the being well seeded right when nobody needs it.

This comments on why bittorrent as is isn't used for live streaming, not why P2P shouldn't be used for live streaming

> Latency matters. In bit torrent if the peer goes away, no big deal, just try again in 5 minutes with another peer, you are downloading in random order, who cares if one piecs is delayed 5 minutes. In a live stream your app is broken if it cuts out for 5 minutes.

First of all, BitTorrent clients do not download in random order or wait 5 minutes. They usually download the rarest block first, but can do whatever they want, whenever they want.

Second, standard HLS sets a nominal segment size of 6 seconds (some implementations will go as high as 10 seconds), and a client will usually cache multiple segments before playing (e.g., 3). This mean that you have 18 seconds before a segment becomes critical.

This is not a difficult thing for a P2P network to handle. You'd adapt things to introduce timing information and manage number of hops, but each client can maintain a connection to a number of other clients and have sufficient capacity to fill a segment if a connection fails. Various strategies could be used to distribute load while avoiding latency penalties.

Low-latency HLS uses much smaller segments and would be more demanding, but isn't impossible to manage.

> BitTorrent punishes people who dont contribute

Private communities punish this behavior, BitTorrent clients do not. Most new downloads will appear as freeriders for a long time, and only over long periods far exceeding the download time will enough compatible seeding opportunities arise for them to contribute in any substantial way.

The network does not need everyone to seed, it only needs enough people to seed.