Confused by PUBG and Battlefield's 'Packet Loss Out' vs 'Packet Loss In' debug graphs? Discover why upload packet drops cause desync, how to find your optimal MTU size using ping -f -l 1472, and how to fix vehicle warping in 2026.
Quick Answer: What Is the Difference Between Packet Loss Out vs In?
In our 2026 tactical military shooter network audits on DCSpeedTest, Packet Loss Out (Upstream) means your PC's inputs (movement, aiming, shooting) are dropping before reaching the game server, caused almost exclusively by local home Wi-Fi interference or upstream bufferbloat. By contrast, Packet Loss In (Downstream) means incoming server state updates (enemy positions, vehicle telemetry) are dropping along your ISP's routing route. When Packet Loss Out occurs, your shots deal zero damage and vehicles rubberband backwards. You can fix both by tuning MTU to 1472 payload size (1500 total) to prevent fragmentation, hardwiring via Cat6A, and activating Cake SQM.
GL.iNet Flint 2 (GL-MT6000) Router with Native Cake SQM
Features dual 2.5GbE ports and quad-core CPU. Eliminates upstream packet drops during heavy firefights and high-speed vehicle chases.
1. The Battlefield & PUBG Diagnostic HUD: Decoding Out vs. In
Both PUBG: Battlegrounds and the Battlefield franchise (DICE Frostbite Engine) feature detailed network performance overlays. When you enable the network debug stats, you are presented with two distinct metrics that confuse thousands of players:
Packet Loss Out (Upstream)
Measures the percentage of packets your computer sent that the server never received. When this spikes, you can look around smoothly, but opening doors takes 3 clicks, weapon swaps fail, and your bullets vanish into thin air.
Packet Loss In (Downstream)
Measures the percentage of packets the server sent that failed to arrive on your PC. When this spikes, enemy players run in place, flying helicopters teleport across the sky, and you die instantly without hearing enemy gunfire.
2. The MTU Size Bottleneck: Why Packet Fragmentation Destroys Shooters
Experiencing packet loss, jitter spikes, or evening ISP throttling? Connect directly to dedicated gaming routes or bypass traffic shaping:
Maximum Transmission Unit (MTU) defines the largest single data packet size (in bytes) that can travel across your network without being broken into pieces.
On standard Ethernet networks, the default MTU is 1500 bytes (consisting of 20 bytes of IP header, 8 bytes of ICMP/UDP header, and 1,472 bytes of actual payload data).
However, if your ISP uses PPPoE (common in older DSL and certain fiber networks), PPPoE adds an 8-byte wrapper, reducing available MTU to 1492. If your router attempts to transmit a 1500-byte UDP entity packet on a 1492 line, the packet is fragmented into two pieces. Because gaming servers require fast UDP delivery, firewalls frequently drop fragmented UDP packets. A single dropped fragment ruins the entire packet, triggering immediate Packet Loss Out in PUBG and Battlefield.
3. Step-by-Step: How to Find Your Optimal MTU with ping -f -l 1472
You can test your network's exact MTU threshold in under 60 seconds using Windows Command Prompt:
- Press
Windows Key + R, typecmd, and press Enter. - Type the following command:
(Theping -f -l 1472 dcspeedtest.com-fflag sets "Don't Fragment", and-l 1472sets the buffer size). - If you see: "Packet needs to be fragmented but DF set", your packets are fragmenting.
- Lower the number by 10 (e.g.
1462,1452) until you get 0% packet loss and normal ping replies. - Add 28 bytes (20 bytes IP header + 8 bytes ICMP header) to your successful number. If 1464 passed, your optimal MTU is $1464 + 28 = 1492$.
- Log into your router's WAN settings and enter this exact value in the MTU Size field.
4. Lab Benchmark: In-Game Packet Loss Across Configurations
| Network Setup | Packet Loss Out | Packet Loss In | Desync Symptoms | Verdict |
|---|---|---|---|---|
| Default Wi-Fi (MTU Mismatch, No SQM) | 8.4% Out | 6.2% In | Severe Hit Blanks / Vehicle Warping | Unplayable (Grade F) |
| Cat6A Ethernet (Default MTU, No SQM) | 2.1% Out | 0.4% In | Occasional Desync in firefights | Playable |
| Cat6A + Optimal MTU + Router Cake SQM | 0.0% Out | 0.0% In | Zero Desync / Instant Hitreg | Tournament Grade (Grade A+) |
Frequently Asked Questions
If your ISP delivers high speeds but your connection drops or suffers from bufferbloat during multi-device use, upgrading these verified components eliminates the bottleneck:
Why does Packet Loss Out only spike when I shoot in PUBG?
Firing automatic weapons generates a sudden burst of high-frequency UDP state packets. If your upstream router buffer is congested, those burst packets are dropped, creating an immediate spike in Packet Loss Out.
Can ExitLag fix Packet Loss In?
Yes. If the downstream packet loss is occurring at a congested intermediate ISP transit exchange, ExitLag's multi-path routing bypasses the damaged hop, delivering packets via a clean private tier-1 backbone.
Where can I test my packet loss percentage?
Run a comprehensive latency and bufferbloat test on DCSpeedTest. Our diagnostic checks both upstream and downstream packet consistency under full load.