Game Lag White Paper › L5 Data center network equipment

Data center link saturation Uplink saturation

Cause ID dc-uplink · Primary owner Infra team (Network infrastructure) · Also Infra team (Server infrastructure)

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When patch distribution, log shipping, or backups share a link with the game, the link fills up.

Why Bulk transfers take over the same link → Effect Link queues and loss grow → On screen Higher ping and teleporting across the whole server

Symptoms

Input lag, Teleporting

Factors

Latency, Packet loss

Who’s affected

Whole server

When

At regular intervals, When crowds gather

Owner

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

Infra team action items

Network: prioritize game traffic (QoS), separate links for bulk transfers, alert on link utilization. Servers/OS: rate-limit backups, log shipping, and deployments, and run them during quiet hours.

On the graph

Hits a ceiling · Link utilization, RTT (ping)

Where to look

Put the utilization of the data center link (uplink) interface (computed from SNMP ifHCInOctets and ifHCOutOctets) and its output drops (ifOutDiscards) on the same timeline as the backup, deployment, and log shipping schedules

Confirmed if

RTT and drops rise across the whole server when link utilization flattens at the bandwidth limit, and those times overlap with bulk transfer jobs

Ruled out if

Per-minute utilization well below the limit but drops still present: “Switch microbursts”

Check with

Infra tools (no game code needed)

Sources

1. RFC 4594: Configuration Guidelines for DiffServ Service Classes IETF
   Handle real-time interactive traffic such as games and bulk transfers such as backups in separate service classes
2. RFC 7567: IETF Recommendations Regarding Active Queue Management IETF
   When more traffic arrives at a device than it can send out, queues build, and excessive queuing is a major cause of latency
3. RFC 2863: The Interfaces Group MIB IETF
   ifHCInOctets and ifHCOutOctets: bytes received and sent on the interface (64-bit); ifOutDiscards: packets discarded without being sent

See also

Same layer: L5 Data center network equipment

• Firewall session table full
• DDoS protection detours and false positives
• Load balancer idle timeout
• Cloud security group connection tracking expiry
• Cloud NAT gateway connection and port limits
• Load balancer skew and misjudged health checks
• Switch microbursts
• Network equipment failover
• Bad cables and port errors
• MTU mismatch (only large packets vanish)

Same symptom (Input lag), other layers

• Rendering load from large crowds L1 Client game process
• Packet processing bottleneck on the main thread L1 Client game process
• V-Sync and the render queue L1 Client game process
• Power saving and thermal throttling L2 Client OS and device
• Other apps on the same device using up bandwidth L2 Client OS and device
• Display, input device, and frame generation latency L2 Client OS and device
• Congested Wi-Fi channel L3 Home network
• Bufferbloat (router queue) L3 Home network

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