Comment by 1vuio0pswjnm7 | Hacker News Reader

Comment by 1vuio0pswjnm7 | Hacker News Reader

"Full mesh: Each call participant sends its media (audio and video) directly to each other call participant. This works for very small calls, but does not scale to many participants. Most people just don't have an Internet connection fast enough to send 40 copies of their video at the same time.

Server mixing: Each call participant sends its media to a server. The server "mixes" the media together and sends it to each participant. This works with many participants, but is not compatible with end-to-end encryption because it requires that the server be able to view and alter the media.

Selective Forwarding: Each participant sends its media to a server. The server "forwards" the media to other participants without viewing or altering it. This works with many participants, and is compatible with end-to-end-encryption."

Imagine an end user who is interested in "very small calls" with friends and family. She is not interested in communicating to an infinitely large audience ("broadcasting"). She never has group calls on Signal with 40 people, even ones with Grandmother and full extended family are well under 40 people. We have to use our imagination because this user does not actually exist.

The imaginary user reads this blog post and she thinks to herself "Full mesh sounds like the best design. There is less/no reliance on a third party, traffic does not need to be sent to an additional third party server." With full mesh, there is no need to mention the caveat "without viewing or altering it", or selectively choosing not to forward it to certain recipients. Full mesh seems to give the user the most control and require the least dependence on third party servers (not necessarily "no dependence", but the least dependance).

Then she reads this line: "Because Signal must have end-to-end encryption and scale to many participants, we use selective forwarding."

Just an FYI full mesh would still require communicating with a third-party server, at the very least for initial networking when joining/leaving a group call.

The whole point of E2E encryption is so that passing data through a third party shouldn't matter in the first place.

And lastly, even when you have just a 1:1 video chat, sending and receiving full resolution/quality multimedia can still be way too much for some peoples' internet connections. UX is extremely important for Signal, as unreliable video chat is a surefire way for those less caring about privacy to hop back over to a privacy-violating alternative.

I feel sorry for those working on bringing security/privacy to everyone, as they have to appease power users and privacy absolutists, along with one's grandmother and the TikTok generation.

Author here.

I guess if there is enough interest from users, we could look into adding a full mesh mode. It's been a year so far with group calls and no one has asked for it, probably because there isn't really much to be gained. Even 1:1 calls, which are p2p, sometimes need to be relayed through a TURN server.

"Even 1:1 calls, which are p2p, sometimes need to be relayed through a TURN server."

What percentage is "sometimes". For example, maybe it is only where two callers are behind the same NAT or some other situation that could be rare relative to the majority of calls.

In any event, it sounds like TURN is not used unless it is needed. The same idea could apply with server forwarding, where forwarding is only used if it is needed. For a small group call, forwarding might not be necessary and full mesh might suffice.

As one user, I would be interested in a full mesh option alongside a server forwarding option.

There is P2P software for small groups I have always used that has a traffic forwarding (relaying) option after the peers are connected, but the default is direct connection, with no need for a relay. The forwarding option is useful for situations where it is needed, but it is not the default. Personally, I have never had to use it.

We don't have a percentage because for 1:1 calls, we don't even know how many calls there are (it's completely p2p), but I've ofte heard quoted somewhere between 5-10% of calls.

Yes, TURN is only used if needed in those cases, and, yes, you could use a forwarding server instead of a TURN server (although with different tradeoffs).

I'll add the full mesh option to our list of options for future work that we discuss regularly.

> We don't have a percentage because for 1:1 calls, we don't even know how many calls there are (it's completely p2p)

Don't the clients have to coordinate through the server to share IPs? (One side at least.)

Yes, that's called "signaling". In the case of Signal, it's done through Signal messages, which pass through a server. But the server doesn't know they are calling related messages. They could be any message.

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