Why Games Use UDP and Why That Makes Loss Painful
Most online games send game state updates over UDP rather than TCP. TCP guarantees delivery by retransmitting lost packets, but retransmission adds at least one round-trip time of additional latency — at 50ms ping, a retransmit takes 50ms minimum. In a real-time game running at 64 updates per second (15.6ms per tick), waiting 50ms for a retransmit means missing 3 full ticks of game state.
UDP delivers packets faster with no retransmission guarantee. Games handle loss at the application layer instead — either by extrapolating (predicting) what happened between lost updates, or simply applying the next received state when it arrives, which causes the characteristic "teleport" effect.
What Happens When a Game Packet Is Lost
When your client doesn't receive a server update on schedule:
- Extrapolation: The client continues moving other players based on their last known velocity and direction. When the next update arrives with the actual position, the client snaps them to the correct location — visible as a teleport or rubber band if the extrapolated position was wrong.
- Your inputs lost: If your input packet (movement, shooting) doesn't reach the server, the server doesn't process your action for that tick. The server may replay it in the next tick's lag compensation, but the timing is off.
- Hit registration errors: If the packet containing your shot doesn't reach the server, the shot is simply not registered regardless of what you saw on your screen.
Packet Loss Thresholds for Gaming
| Packet Loss | Effect on Competitive Gaming | Effect on Casual Gaming |
|---|---|---|
| 0% | Ideal | Ideal |
| 0.1–0.5% | Barely perceptible, occasional minor stutter | Generally unnoticeable |
| 0.5–1% | Noticeable — occasional rubber band, suspect hit reg | Minor annoyance |
| 1–3% | Frequent issues, competitive play degraded | Regular stuttering |
| 3–5% | Game often unplayable competitively | Frustrating |
| 5%+ | Unplayable | Unplayable |
Common Causes and Fixes
- Wi-Fi interference: The most common home cause. Wi-Fi packet loss spikes when microwave ovens, neighboring networks, or physical obstructions interfere. Fix: use wired Ethernet.
- Overloaded router: Routers with insufficient CPU/RAM under heavy load drop packets internally. Fix: reboot router, reduce simultaneous connections, upgrade if persistent.
- ISP infrastructure: Congested nodes between you and the game server drop packets during peak hours. Fix: traceroute to identify which hop loses packets; report to ISP with evidence.
- Cable or ethernet port issues: A damaged cable or failing NIC causes intermittent packet loss that appears random. Fix: replace the cable, try a different port on router/switch.
Frequently Asked Questions
What percentage of packet loss is acceptable for gaming?
Above 0.5% is noticeable in competitive play. At 64-tick, 1% loss means losing ~one packet per 1.5 seconds — visible as a skip or teleport. Streaming tolerates 1–5% invisibly due to TCP and large buffers. Gaming cannot buffer ahead, making it far more sensitive to loss.
How do I know if packet loss is on my network or the ISP's?
Run a traceroute to the game server IP. If loss appears at hop 1–2 (your router), the problem is local — check cables, router load, and Wi-Fi. If loss appears at hop 3+, it's ISP or transit. Report the traceroute output to your ISP as evidence. In-game packet loss meters (CS2, Valorant developer console) confirm loss at the server connection specifically.