4 ms·

I down voted against the example. It's really bad because latency has no relevance to FPS and games can actually approach 100 ms and work just fine (consider re

I down voted against the example. It's really bad because latency has no relevance to FPS and games can actually approach 100 ms and work just fine (consider rendering time and TV delay as well). It's fine because the latency is constant. Your brain internalizes that there is a delay between moving buttons and things happening. Your brain internalizes that you need to shoot where things are going not where they are now. If anything, latency is an example that consistency is more important than speed.

Terretta 6y ago
Latency has no relevance to FPS (frames per second, not first person shooter)? Why do gamers care about not just TV frame rates, but how many frames delay (latency) come from the TV's video scalar / processor? When dealing with round trip times (RTT) for TCP or video gaming, latency limits the number of round trips or control loops per second and the gap between input and action. To your consistency point, agree -- jitter matters a lot to human perception and response too, why so many games "lock" to 30 or 60 fps rather than vary at rates above 30 or 60. Also, it was not an example. It was an analogy to put the differences in milliseconds into amounts of time that matter to a broader set of people than networking times matter to.
- user5994461 6y ago
  Latency is not related to frame per seconds, yes. You could feed a thousand frames per second to a TV and the TV can have 100 ms latency (delay to display a frame after it received it). You could feed 30 frames per second to the same TV and it'd still have a 100 ms latency. The latency is rarely advertised. It's highly variable per TV and per image. There's the time it takes to start displaying an image and the time until the image is fully set (it is much longer to go white to black than white to grey).
  - Terretta 6y ago
    I take it you're explaining this for our readers. That said, anyone who wonders why they can't download a file over TCP/IP at gigabit speeds on their gigabit FIOS is realizing there is a link between latency and throughput (network frames per second). Put another way, latency is not related to number of frames that can be sent at once (bandwidth) but if RTT factors in flow control, those two work together to limit throughput.
    - user5994461 6y ago
      That's the thing, there isn't a link between latency and throughput in a pipe. TCP is not exactly a pipe. It's sending a message and waiting to receive a confirmation back before sending more. It's control logic to control the flow in a pair of pipes, that's affected by the latency back and forth. UDP doesn't do that. The Ethernet link doesn't do that. The HDMI link to a TV doesn't do that.
      - Terretta 6y ago
        If you're still writing to enlighten readers, this last information may risk losing them, as it's no longer relevant to their real world experience. In their real world experience, these are linked, as the control logic you acknowledge is affected by latency impacts their download, which is over TCP/IP. But this is a diversion, as I was not attempting the make that connection. I was relating the size of 15 ms and 100 ms to an experience where people can perceive those intervals. If, by contrast, you're showing me you understand this, sounds like you do. We had developed an internal tool before Aspera's FASP[1], for our clients to deliver us video, and us to distribute content among hubs at scale, at speeds that saturated links. Understanding the mechanics and limiting factors of information propagation was necessary to be on that team. Turns out most devs don't have a great grip on the physics -- in the most common mental model, everything happens instantly. And so things get slow. 1. https://en.wikipedia.org/wiki/Fast_and_Secure_Protocol https://en.wikipedia.org/wiki/Fast_and_Secure_Protocol
        user5994461 6y ago
        Well, we went from video games to TV to TCP. That's quite a lot of different things, no wonder we lost people on the way. =) There is one thing I'd like to insist on though, I'm not sure whether people could actually notice 100 ms of latency after user input. You assume that users do? but I don't think they necessarily do. I think the full delay between when you press a button on a gamepad and when the frame changes on the TV is somewhere around that and gaming consoles are generally considered very usable. (Of course latency in computer networks is a different matter). My daily job among other things is to optimize software and networking infrastructure covering 4 continents and 50 datacenters. I'd say I have a certain grasp of networking. ;)

Terretta 6y ago

Latency has no relevance to FPS (frames per second, not first person shooter)? Why do gamers care about not just TV frame rates, but how many frames delay (latency) come from the TV's video scalar / processor? When dealing with round trip times (RTT) for TCP or video gaming, latency limits the number of round trips or control loops per second and the gap between input and action. To your consistency point, agree -- jitter matters a lot to human perception and response too, why so many games "lock" to 30 or 60 fps rather than vary at rates above 30 or 60. Also, it was not an example. It was an analogy to put the differences in milliseconds into amounts of time that matter to a broader set of people than networking times matter to.

user5994461 6y ago
Latency is not related to frame per seconds, yes. You could feed a thousand frames per second to a TV and the TV can have 100 ms latency (delay to display a frame after it received it). You could feed 30 frames per second to the same TV and it'd still have a 100 ms latency. The latency is rarely advertised. It's highly variable per TV and per image. There's the time it takes to start displaying an image and the time until the image is fully set (it is much longer to go white to black than white to grey).
- Terretta 6y ago
  I take it you're explaining this for our readers. That said, anyone who wonders why they can't download a file over TCP/IP at gigabit speeds on their gigabit FIOS is realizing there is a link between latency and throughput (network frames per second). Put another way, latency is not related to number of frames that can be sent at once (bandwidth) but if RTT factors in flow control, those two work together to limit throughput.
  - user5994461 6y ago
    That's the thing, there isn't a link between latency and throughput in a pipe. TCP is not exactly a pipe. It's sending a message and waiting to receive a confirmation back before sending more. It's control logic to control the flow in a pair of pipes, that's affected by the latency back and forth. UDP doesn't do that. The Ethernet link doesn't do that. The HDMI link to a TV doesn't do that.
    - Terretta 6y ago
      If you're still writing to enlighten readers, this last information may risk losing them, as it's no longer relevant to their real world experience. In their real world experience, these are linked, as the control logic you acknowledge is affected by latency impacts their download, which is over TCP/IP. But this is a diversion, as I was not attempting the make that connection. I was relating the size of 15 ms and 100 ms to an experience where people can perceive those intervals. If, by contrast, you're showing me you understand this, sounds like you do. We had developed an internal tool before Aspera's FASP[1], for our clients to deliver us video, and us to distribute content among hubs at scale, at speeds that saturated links. Understanding the mechanics and limiting factors of information propagation was necessary to be on that team. Turns out most devs don't have a great grip on the physics -- in the most common mental model, everything happens instantly. And so things get slow. 1. https://en.wikipedia.org/wiki/Fast_and_Secure_Protocol https://en.wikipedia.org/wiki/Fast_and_Secure_Protocol
      - user5994461 6y ago
        Well, we went from video games to TV to TCP. That's quite a lot of different things, no wonder we lost people on the way. =) There is one thing I'd like to insist on though, I'm not sure whether people could actually notice 100 ms of latency after user input. You assume that users do? but I don't think they necessarily do. I think the full delay between when you press a button on a gamepad and when the frame changes on the TV is somewhere around that and gaming consoles are generally considered very usable. (Of course latency in computer networks is a different matter). My daily job among other things is to optimize software and networking infrastructure covering 4 continents and 50 datacenters. I'd say I have a certain grasp of networking. ;)