Quick answer: Unreal Iris sending snapshots larger than MTU causing visible packet loss on cellular? Fragment over UDP fragmented at the network layer - keep snapshots under MTU - 64 bytes.
Mobile players experience hitches every few seconds. Server-side log: large packet, may fragment.
Cap snapshot size
net.iris.MaxSnapshotSize 1024Below typical MTU (1500) minus IP/UDP/headroom. Cellular networks drop fragments aggressively.
Split state across snapshots
Iris supports partial-state delta. Half the state per snapshot; full state across two snapshots.
Profile with ICMP
Ping with -M dont -s 1472 to find effective MTU. Mobile is often 1400; cap snapshots there.
“MTU is a network-layer concept. Replication that ignores it pays.”
Test on cellular networks, not just office WiFi. The bugs are different; both must be tested.