Game Lag White Paper › Problems only some players hit

Validation false positives concentrated on one ISP Anti-cheat / movement validation false positives on bad ISPs

Cause ID pt-isp-validation · Primary owner Game team (Server development) · Also Infra team (Network infrastructure)

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Players on high-jitter connections have their inputs arrive in bunches, so they often trip the server’s speed and cooldown checks.

Why Jitter on a specific ISP’s or region’s connections rises in the evening → Effect The server judges valid inputs that arrived in a bunch as speeding or cooldown violations → On screen Only that ISP’s players get rubber-banding and rejected skills, and in bad cases the server kicks them (disconnect)

Symptoms

Rubber-banding, Dropped action / rollback, Disconnect

Factors

Jitter

Who’s affected

Specific region/ISP, Just me

When

Evening peak hours, While moving or changing zones

Owner

Primary owner Game team (Server development) · Also Infra team (Network infrastructure)

Game team action items

Check against an allowance accumulated over several seconds, loosen thresholds based on connection quality (ping, jitter), add a warning stage before a forced disconnect, spread bunched inputs evenly across ticks with a per-player input buffer to cut false positives at the source.

Infra team action items

Check loss rate and jitter distribution per ISP by time of day and share them with the game team, check the path through that ISP (bidirectional mtr), reroute or escalate to the ISP if needed.

On the graph

High at certain hours · Validation rejections and forced disconnects per ISP (ASN), jitter per ISP

Where to look

Server logs of validation rejections, corrections, and forced disconnects tagged with the ISP (ASN) of the connecting IP and the time, counted by ISP and time of day. The infra team runs bidirectional mtr toward that ISP at the same time to check jitter and loss

Confirmed if

Rejections and forced disconnects concentrate on one ISP and rise in the evening, that ISP’s jitter is high at the same time, and movement summed over a few seconds stays within the rules

Ruled out if

Only specific accounts repeat regardless of ISP: real cheating possible. Rising across all ISPs together: a server-side cause where lagging server ticks apply commands in bunches (tick overrun)

Check with

Game server or client logs and metrics

Sources

1. Source SDK 2013: player.cpp Valve
   A per-tick command budget stops speed hacks; a developer comment says stricter limits cause stutter for legitimate players too
2. RFC 2697: A Single Rate Three Color Marker IETF
   Token bucket: judged by average rate and allowed burst size
3. Understanding Networked Movement in the Character Movement Component for Unreal Engine Epic Games
   When client and server timestamps differ by too much, the move is discarded or handled by a time discrepancy resolution procedure; computing with server time prevents speed hacks

See also

Same layer: Problems only some players hit

• A lagging player moves in bursts on others’ screens
• Fast-forward on servers that process on arrival
• Per-player input buffer size
• One lagging party member and boss mechanics
• A lagging client controls the monster
• Bloated data on one character
• Different channel, instance, or phase
• Spawn messages dropped during loading
• AOI registration race
• Lost baseline snapshot
• Missed despawn message (ghost entity)
• Spawn data lost in the burst after entering
• Entity ID reuse mix-up
• Fixed UDP port collision
• Sessions keyed by IP or device (bug)
• Multi-client restriction
• Background window throttling
• Simultaneous access to cache or asset files
• Streaming failure from memory or VRAM shortage
• Different display settings
• Client version or data mismatch
• Per-connection send budget and priority
• Entities held back by clock estimate error

Same symptom (Rubber-banding), other layers

• Client-side prediction mismatch L1 Client game process
• Wi-Fi interference and weak signal L3 Home network
• Peak-hour congestion at peering links L4 Internet path
• One faulty ECMP path L4 Internet path
• Bad cables and port errors L5 Data center network equipment
• NIC interrupts concentrated on one core L6 Server network card
• Zone transfer (handoff between servers) L13 Server architecture and operations
• Matchmaking and region assignment errors L13 Server architecture and operations

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