Can someone explain Desync?

[nate03]

Hello,
I understand how EMI can cause latency so that for example ur mouse feels unnormal (its explained in the sticky note of this forum). But more often than not, people describe that they have Desync that seems to be network related. In other words, the opponent sees you at a different spot than you actually are - conversely this means you also see the enemy in the wrong spot, leading to the infamous dying behind walls, having no chance to react to peeks, enemies feeling like they are donk etc. - this is the kind of stuff I read here. I have personally seen clips of people experiencing this that goes beyond normal ping compensation/peekers advantage, so I dont doubt that this is a real problem (besides, I experienced this myself).

However, wouldnt u see way more obvious signs first, like horrible RTT Jitter or Packet Loss? If Interference can be so strong to cause a Desync like this, then surely it would also cause Jitter or Packet Loss (those are WAY more frequent issues). But people say they have stable internet, no packet loss/very low jitter and still experience this Desync.
Lmk if anyone has a logical explanation

[Unreazz]

In my case, I was able to clearly link desync issues to the network path at two different locations.

At my old place, I was on cable internet. I managed to fix the desync almost completely by using a VPN. After that, the problem basically disappeared, which strongly suggests that routing and traffic handling played a major role.

At my new location, I only have VDSL. There, a VPN didn’t really help. However, after contacting my ISP, they manually switched my port on the DSLAM and performed a full line reset. After that, I had around three days of completely smooth, desync-free gameplay. Then, slowly, the issues started to come back.

This strongly points toward the line management and stability profiles used by ISPs, rather than classic peering problems.

On DSL/VDSL lines, providers use systems like Dynamic Line Management (DLM), interleaving, and forward error correction to keep unstable lines “reliable.” These systems constantly monitor noise, retransmissions, and error rates, and then automatically adjust the line profile.

If the line shows instability or noise, the system will increase:

Interleaving depth

Error correction overhead

Buffering and retransmission mechanisms

The result is:
You no longer see packet loss.
You no longer get disconnects.
Speed looks fine.
But latency consistency gets worse.

For gaming, this is often worse than occasional packet loss.

Instead of losing packets, you now get:

Micro-delays

Jitter

Variable latency

Inconsistent packet timing

All of this directly translates into desync, delayed hit registration, and “floaty” or unresponsive gameplay.

That’s also why many people don’t see obvious issues in speed tests or basic ping tests anymore. Modern networks are heavily optimized to hide instability from normal users. Everything is smoothed out by algorithms.

But competitive or latency-sensitive applications feel it immediately.

In my case, the temporary improvement after the DSLAM port change and line reset shows this clearly. Right after the reset, the line was running on a clean, relaxed profile. Over time, as the system detected “imperfections” again, it slowly tightened the profile and reintroduced more correction and buffering.

From the ISP’s perspective, this is working as intended.
Their priority is:

Stability

Low support cases

No disconnects

Acceptable average latency

Not low jitter or optimal real-time performance.

So unless your line is completely broken, they usually won’t change anything manually. The system is automated, and for most customers, it’s “good enough.”

Unfortunately, for online gaming, “stable” does not always mean “good.”

It often means:

Stable, but delayed.
Reliable, but inconsistent.
Clean metrics, bad experience.

That’s why tools like VPNs, alternative routing, or fresh line profiles can temporarily improve things — they bypass or reset parts of this system. But long-term, the automated management usually takes over again.

In my experience, modern ISPs optimize for average users and video streaming, not for low-jitter real-time traffic. And once your line gets classified as “needs stabilization,” your gaming performance will almost always suffer — even if everything looks fine on paper.

[Maelstrom]

a
The result is:
You no longer see packet loss.
You no longer get disconnects.
Speed looks fine.
But latency consistency gets worse.

For gaming, this is often worse than occasional packet loss.

Instead of losing packets, you now get:

Micro-delays

Jitter

Variable latency

Inconsistent packet timing

All of this directly translates into desync, delayed hit registration, and “floaty” or unresponsive gameplay.

That’s also why many people don’t see obvious issues in speed tests or basic ping tests anymore. Modern networks are heavily optimized to hide instability from normal users. Everything is smoothed out by algorithms.

But competitive or latency-sensitive applications feel it immediately.

In my case, the temporary improvement after the DSLAM port change and line reset shows this clearly. Right after the reset, the line was running on a clean, relaxed profile. Over time, as the system detected “imperfections” again, it slowly tightened the profile and reintroduced more correction and buffering.

From the ISP’s perspective, this is working as intended.
Their priority is:

Stability

Low support cases

No disconnects

Acceptable average latency

Not low jitter or optimal real-time performance.

So unless your line is completely broken, they usually won’t change anything manually. The system is automated, and for most customers, it’s “good enough.”

Unfortunately, for online gaming, “stable” does not always mean “good.”

It often means:

Stable, but delayed.
Reliable, but inconsistent.
Clean metrics, bad experience.

That’s why tools like VPNs, alternative routing, or fresh line profiles can temporarily improve things — they bypass or reset parts of this system. But long-term, the automated management usually takes over again.

In my experience, modern ISPs optimize for average users and video streaming, not for low-jitter real-time traffic. And once your line gets classified as “needs stabilization,” your gaming performance will almost always suffer — even if everything looks fine on paper.

This is a good reply - but IMO there is still the issue where users will play games with a clean netgraph (showing each packet, basically flat, etc) and still see issues. For me I will try QL occasionaly and my ping is 20 with +- 5 ms on each side frequently. I've noticed that players with very high frequency jitter, with lots of noise (ping rapidly changing between 22, 21, 24) on each packet generally have a much easier time and are much more slippery to hit.

My opinion, after trawling through lots of discussions about QLs architecture and netcode implementation is that the specifics of people'
s network connection isn't really explored since most users don't have much control over it. There is also the assumption that if you have a stable, low ping, that that is the most ideal condition, and then some analysis about whether packet loss or jitter is present, but never more specific than that.

It's probably the case that there is some 'advantageous' network condition, and that there are big differences in experience with different kinds of jitter (e.g. high frequency low magnitude jitter, vs alternatives), and these explain the weird hitreg and movement issues I've noticed in online games.

[Slender]

All you need to know to avoid wasting of your precious time is that internet not reason of desync.

[Maelstrom]

All you need to know to avoid wasting of your precious time is that internet not reason of desync.

All you need to do is to test locally vs online play for extended periods and be precise about your symptoms to determine whether your desync is internet related.

[Slender]

All you need to know to avoid wasting of your precious time is that internet not reason of desync.

All you need to do is to test locally vs online play for extended periods and be precise about your symptoms to determine whether your desync is internet related.

2 pc connected via lan cable. same desync.

[Maelstrom]

All you need to know to avoid wasting of your precious time is that internet not reason of desync.

All you need to do is to test locally vs online play for extended periods and be precise about your symptoms to determine whether your desync is internet related.

2 pc connected via lan cable. same desync.

What are your symptoms specifically, and why are you presuming that the same is the case for OP?