Network Engineering Path MTU • MSS Clamping • Tunnel Encapsulation

MTU, MSS & VPN Overhead Calculator

Determine optimal Maximum Segment Size (MSS) clamps and tunnel MTU parameters to eliminate packet fragmentation and TCP connection stalls over VPNs.

Physical Underlying Interface MTU

bytes

Encapsulation / Tunnel Protocol

IP Protocol Version

Recommended Safe MSS Clamp

1360 bytes

Tunnel MTU: 1420 bytes

Encapsulation Overhead: 80 bytes

TCP/IP Headers: 40 bytes (IPv4 + TCP)

Wire Throughput Efficiency: 94.6%

Linux iptables MSS Clamping Rule:

iptables -t mangle -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --set-mss 1360