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Comment by pedrocr | Hacker News Reader

The first-person shooter crowd has probably run into these limits so that's a good market to go see what works and what doesn't. Your music example may be a little misleading. Although we can detect small delays (10 or 20ms) our reaction time for input is an order of magnitude greater (100ms or more), so we may be able to tell a note is off by 10ms but we only do it 100ms after the fact. Depending on what you're doing that distinction can be important. For human communication for example a 500ms roundtrip time would still allow a conversation easily.

Your math is also slightly off because the speed of light in fiber optic is only 200000km/s, so the minimum latency between two opposite points on the globe using fiber is 100ms.

PS: The circumference of the earth is also 40 thousand km not 40km, so I suppose the correct notation is 40Mm, although that's unusual.

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> The first-person shooter crowd has probably run into these limits

Too true. Early on, when people were still connecting over modems, the ping times were pretty much guaranteed to be well north of 100ms, even to servers that were relatively local. As universities started getting equipped with expensive low-latency/high-bandwidth internet connections players started getting <100ms pings and as a result these "low ping bastards" (lpb) ended up dominating servers.

Very quickly hpb and lpb servers developed to serve and enforce a bifurcation of the two groups of technology users. Scripts usually ran to kick/ban lpb players from hpb server and to warn hbp players they were on an lpb server.

Importantly, if you get get <100ms ping times, the predictive engines in the games (designed to help "help ping bastards" or hpb players) solved most of the rest. A good player with a <50ms ping was virtually unstoppable.

You could also tell when certain players were likely cheating, Team Fortress snipers with >200ms pings but incredibly high kill:shot ratios were usually the form it took on the games I played. From their perspective, everybody was jumping around in huge gaps and prediction by the player, even once you got used to the lag, would have been virtually impossible.

I used to work at an ISP connected to a tier-1 provider connected to MAE-EAST and routinely had 10-20ms ping times and enjoyed high placement on leaderboards for quite a while.

More recently, with my in-laws now on the other side of the planet, and having spent some time conversing on Satellite Communication links, 500ms for voice communications is doable, but definitely disruptive.

On a sidenote, I checked pingtimes from my FiOS connection to Japan (yahoo) and to a local server and inside my home network.

Home Network: <1ms

Local site (10 minutes away): <25ms 12 hops

Japan: <200ms 16 hops

Even if the reaction time is higher than what we detect as a latency, it's still a bad news, but delivered ... later. :)

I left 300000 km/s, because I thought that maybe this is the absolute theoretical limit (there might be some breakthrough in reflective materials, who knows?).

Sorry for the typo of the circumference of the earth, I think I've fixed it before your comment. https://news.ycombinator.com/item?id=7862387

>Even if the reaction time is higher than what we detect as a latency, it's still a bad news, but delivered ... later. :)

It would be hard to do a distributed band. It's an interesting case because it's not a question-response situation where the roundtrip is crucial, because for the most part each musician is playing independently and only listening to the rest to stay in sync. I wonder if you could do this:

1) Have every member stream to every other member directly with an accurate absolute timecode (good NTP-adjusted or even GPS clocks)

2) Have every member mix in all the streams using the absolute time code and buffering as much as needed for the slowest stream (so you'd have 100ms of buffer in the worst case).

This would give you a synced up band where every member listens to the same mixed stream and yet everyone is listening to themselves on a slight delay. I wonder how well our brains could cope with that introduced delay and if it would then screw up live performance, or if we can adapt to that sort of thing quickly.

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