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Author Topic: Interleave - psychology  (Read 958 times)

boost

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Re: Interleave - psychology
« Reply #15 on: July 06, 2018, 08:50:40 PM »

I'm not sure there's a psychological aspect to it.

Latency at the transport layer is sometimes magnified at the application layer. When you read about people 'whinging' because they're seeing a mere +10ms on their round trip game, you can almost guarantee it *feels* like an extra 250ms~ in their game or telnet session.

Visual reaction times for regular gamers have been measured in the 160 - 280ms region, however, auditory reaction times are lower still and start around 110ms. When you start adding 10 - 20ms for each datagram, those that are hypersensitive to such changes have to endure this state of incongruence. They have to retrain their eyes and ears to some new, unknown and somewhat unpredictable value.

What makes this worse, is when developers think it's a great idea to build lag compensation into the game. Please stop doing this :P
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spring

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Re: Interleave - psychology
« Reply #16 on: July 06, 2018, 09:18:25 PM »

playing at 30ms vs 80ms definitely feels entirely different for action games that don't use lag compensation, and makes 80ms look like 200ms [same ratio as 30ms vs 80ms], so 46ms is going to be noticeable compared to 30ms, or 54ms, 62ms, and so on. playing at 150ms due to distance lag it's less of a % difference, so 180ms is somewhat negligible in the context [speed of light not fast enough :o]

What makes this worse, is when developers think it's a great idea to build lag compensation into the game. Please stop doing this :P
yeah it makes it even more unfair when playing with lags, for the one that's more skilled, so the lags lessen the skill factor - despite being more "fun" :-\
« Last Edit: July 06, 2018, 09:33:22 PM by spring »
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ejs

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Re: Interleave - psychology
« Reply #17 on: July 06, 2018, 09:35:29 PM »

@boost

Have you seen this?
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Weaver

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Re: Interleave - psychology
« Reply #18 on: July 06, 2018, 11:19:12 PM »

I don't know why j0hn says that interleaving "takes 10% overheads off your sync speed". That simply is not true, from my reading of the standards docs for ADSL. Interleave factors not equal to 1 do not have any associate protocol overhead. See G.992.3 p 31 framing picture. I am not familiar with VDSL2 but a brief squint at the G.993.2 equation for NDR on page 74 does not mention interleave depth parameter and description of convolutional interleaver on p64 have not mention of overheads. Maybe I have missed something. Perhaps j0hn will explain.

The point made about latency affecting slow start is indeed a good one. That indeed critically affects effective throughout with small downloads. They are beyond help anyway as using TCP for small objects is just a performance disaster, and this is why HTTP 2 has fixed this by getting rid of the multiple slow-starts iirc.

[Moderator edit to fix an incorrect auto-correction.]
« Last Edit: July 06, 2018, 11:45:58 PM by burakkucat »
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j0hn

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Re: Interleave - psychology
« Reply #19 on: July 07, 2018, 03:10:58 AM »

I don't know why j0hn says that interleaving "takes 10% overheads off your sync speed". That simply is not true, from my reading of the standards docs for ADSL.

It is very true with OpenReach's implementation on VDSL2.
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boost

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Re: Interleave - psychology
« Reply #20 on: July 08, 2018, 04:13:17 PM »

@boost

Have you seen this?

All I see is a thread full of frustration.

Sky. Believe in better!
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CarlT

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Re: Interleave - psychology
« Reply #21 on: July 09, 2018, 12:23:18 PM »

Given that the server is allowed to fire up multiple parallel TCP connections (in http 1.x anyway, not sure about http 2.0) as you say if you had objects that depend on one another, then that would be bad.

A server is not allowed to fire up multiple parallel TCP connections. It's not allowed to fire up any TCP connections in the normal browsing scenario.
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Weaver

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Re: Interleave - psychology
« Reply #22 on: July 09, 2018, 12:56:19 PM »

I mistyped that, I meant client of course. What I wrote was complete nonsense.
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kitz

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Re: Interleave - psychology
« Reply #23 on: July 10, 2018, 03:04:29 AM »

I don't know why j0hn says that interleaving "takes 10% overheads off your sync speed". That simply is not true, from my reading of the standards docs for ADSL.

For FTTC it makes a BIG difference to your sync speed.

Last time I was interleaved, I immediately went from 73.9Mbps to 67.8Mbps.  Bear in mind that was "interleaved low" profile.   "Interleaved high" profile would reduce the sync speed further as the level of INP is increased.  So 10% is probably a fair figure to use as a rough example.

It's not so much interleaving that reduces the sync speed, but rather the fact RS encoding that comes with interleaving incurs overheads which reduces the available sync speed.

On adsl1 'Interleaving' on a line syncing at 8128 would reduce the sync to 7616.   When I was on BE* Interleaving reduced line speed by just over 2Mbps.
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Chrysalis

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Re: Interleave - psychology
« Reply #24 on: July 10, 2018, 09:44:49 AM »

Why is it that some people really really hate interleaving on their DSL lines? Gamers are one well-known group. Is that all though?

Its simple really.

RTT is a key factor in performance, for most use cases its more important than burst speed.

e.g. a 10ms 10mbit connection for most things on the internet will offer smoother performance than a 100ms 100mbit connection.

a DNS lookup requires at least 2 x RTT to get a result back to the client.  A website could easily have a dozen DNS lookups.
Establishing a connection to a webserver, again multiples of RTT before you even start downloading data.
Streaming will ramp up to higher throughput faster when RTT is lower.
Things like FTP where every command packet has to be acknowledged speed up significantly when RTT is lower.
Then there is of course gamers twitch shooter gamers are hyper sensitive to latency.

Where its not so important and burst speed becomes king is things like bulk downloads, so steam downloads, PSN downloads etc.  Although RTT can still be a bottleneck if RWIN is saturated.

Very low burst speed like adsl1 speeds will be a bottleneck for various use cases, so my above post is assuming your burst speed is already at least about 15mbit.
« Last Edit: July 10, 2018, 09:47:38 AM by Chrysalis »
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ejs

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Re: Interleave - psychology
« Reply #25 on: July 10, 2018, 04:43:30 PM »

Wouldn't a normal UDP DNS question and answer be one RTT?
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Chrysalis

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Re: Interleave - psychology
« Reply #26 on: July 10, 2018, 08:43:38 PM »

yeah sorry, RTT been both ways it 'can' be one RTT depending on the lookup been carried out as well as the resolver/forwarder configuration to optimise lookups.
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ejs

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Re: Interleave - psychology
« Reply #27 on: July 10, 2018, 09:08:49 PM »

I still think most people are substantially underestimating the psychological aspects.

Do you think people would be campaigning for interleaving to be removed if all lines had interleaving? I don't think people would be complaining about ECI cabinets so much if ECI were all that was installed. The problem is that one thing (ECI cabinets, interleaving) is not as good as the other thing (Huawei cabinets, no interleaving), and that's not fair.
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Westie

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Re: Interleave - psychology
« Reply #28 on: July 10, 2018, 09:48:50 PM »

Quote
The problem is that one thing (ECI cabinets, interleaving) is not as good as the other thing (Huawei cabinets, no interleaving), and that's not fair.
"Good" in this context depends on your perspective. Interleaving might be "bad" for latency, but "good" for error correction.

Life isn't fair: this is just another example of the desires of one group of people being given preference over the desires of another group. It feels "right" if you are in the first group, but "wrong" if you are in the second group.
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Weaver

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Re: Interleave - psychology
« Reply #29 on: July 11, 2018, 05:09:18 AM »

I was intentionally not counting ping-pong type cases as I was only talking about throughput, and the word doesn't imo really apply if you are not keeping the line 100% in use any way. I mean if you choose to send packets more slowly than you can, then you cannot say you have a slow line. aim talking about the capacity of a link  not the speed of any use case, if you see what I mean.

That is not to say that RTT is not important or that stop-and-wait type scenarios are not important, indeed no, it's just that for my present discussion that would be a different question, one is about links and the other is about use cases.

I think Kitz is actually agreeing with me, sometimes the engaging of interleave is accompanied by extra RS codword bloat? Is that correct. about that is just a choice made by the designers, it does not mean that the reduction in throughput was caused by interleave itself - is that correct?

So if I am understanding Kitz correctly, then I am disagreeing with J0hn and maybe getting an understanding of his opinion?

So could the answer be that you happen to get an additional phenomenon kicking into place when you choose a setting called 'interleave' but the name is misleading because it comes with a free side dish of onion rings that you did not order?
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