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VPN Encryption Overhead & Tunnel MTU Calculator (WireGuard, IPsec, OpenVPN)

Calculate cryptographic encapsulation overhead, optimal tunnel MTU, TCP MSS clamping, and effective payload throughput for WireGuard, IPsec, and OpenVPN.

Input Parameters

Try Example:
Byte
5769000
Mbps
11000

Calculation Results

VPN Tunnel Payload Efficiency (%)93.33%
Physical WAN Interface MTU
1,500 Bytes
Outer Carrier IP Header Size
20 Bytes
VPN Encapsulation & Cipher Overhead
40 Bytes
Total Tunnel Header Overhead per Packet
60 Bytes
Optimal VPN Tunnel Interface MTU
1,440 Bytes
Optimal TCP MSS Clamping Value
1,400 Bytes
Inner TCP Segment Payload Size
1,400 Bytes
Protocol Payload Transmission Efficiency
93.33 %
Effective Usable Payload Throughput
93.33 Mbps
Bandwidth Consumed by Encapsulation
6.67 Mbps
Want to compare 2 design options side-by-side (e.g., Scenario A vs Scenario B)?
⚡ Production Security & Ops Standard
Debian 12 / Ubuntu 24.04 LTS + Nftables + Systemd Timer
CIS Benchmark Level 1 • Non-Root SSH Key-Only + Fail2ban/CrowdSec

Validate firewall rulesets and cron timers in staging before production rollout.

Overhead, MTU & Throughput Comparison Across VPN Protocols
VPN Protocol & CipherTunnel Encapsulation OverheadOptimal VPN Tunnel Interface MTUOptimal TCP MSS Clamping ValueEffective Usable Payload Throughput
WireGuard (UDP 8B + WG Header 32B + Poly1305 16B)60 Bytes1,440 Bytes1,400 Bytes93.33 Mbps
IPsec ESP AES-GCM Native (Proto 50)66 Bytes1,434 Bytes1,394 Bytes92.93 Mbps
IPsec ESP AES-GCM + UDP NAT-T (4500)74 Bytes1,426 Bytes1,386 Bytes92.4 Mbps
OpenVPN 2.6 Data Channel AEAD (UDP)68 Bytes1,432 Bytes1,392 Bytes92.8 Mbps
OpenVPN Data Channel (TCP)80 Bytes1,420 Bytes1,380 Bytes92 Mbps
GRE Tunnel (24B) + IPsec ESP NAT-T98 Bytes1,402 Bytes1,362 Bytes90.8 Mbps
MTU & TCP MSS Clamping Rules (RouterOS & Linux)
# Konfigurasi Interface MTU & TCP MSS Clamping (MikroTik RouterOS v7 & Linux)
/interface wireguard set [find] mtu=1440
/ip firewall mangle add chain=forward protocol=tcp tcp-flags=syn action=change-mss new-mss=1400 passthrough=yes comment="VPN MSS Clamping"
# Linux iptables equivalent:
iptables -t mangle -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --set-mss 1400
Multi-Vendor CLI & Packet Flow

Multi-Vendor Config Translator & Interactive Packet Flow Visualizer

Interactive Packet Flow Pipeline (Click Stage to Inspect)WAN ➔ Prerouting/NAT ➔ Filter/QoS ➔ LAN
1. Client TCP SYNDefault MSS 1460B2. TCP MSS ClampingClamp MSS -> 1400B3. Tunnel EncapsulationTunnel MTU 1440B4. ISP WAN TransitNo PMTUD Blackhole
1. Client TCP SYN: LAN host initiates TCP 3-way handshake advertising standard 1460-byte MSS.
# MikroTik RouterOS v7 — WireGuard MTU 1440 & TCP MSS Clamping (1400)
/interface wireguard
add name=wg-s2s mtu=1440 listen-port=51820
/ip firewall mangle
add chain=forward out-interface=wg-s2s protocol=tcp tcp-flags=syn tcp-mss=1401-65535 \
    action=change-mss new-mss=1400 passthrough=yes comment="Clamp TCP MSS to 1400"
add chain=forward in-interface=wg-s2s protocol=tcp tcp-flags=syn tcp-mss=1401-65535 \
    action=change-mss new-mss=1400 passthrough=yes
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Technical Accuracy Note: Calculation results are engineering estimates based on standard RFC/IEEE/ITU-T models. Actual field performance may vary due to protocol overhead, hardware specifications, and environmental factors.

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How to Use This Tool

  1. Enter the physical WAN interface MTU (1500 for standard Ethernet or 1492 for PPPoE fiber links) and select the outer IP version (IPv4 or IPv6).
  2. Choose the active VPN tunnel protocol (WireGuard, IPsec ESP NAT-T, IPsec Native, OpenVPN UDP/TCP, or GRE + IPsec) and enter the link speed in Mbps.
  3. Review the optimal Tunnel MTU, TCP MSS clamping value, protocol payload efficiency, and copy the generated MikroTik RouterOS or Linux iptables mangle rules.

Worked Example: WireGuard over Standard Ethernet (MTU 1500, 100 Mbps)

Worked example: A 1500-byte Ethernet WAN link running WireGuard over IPv4 incurs 60 bytes of total tunnel overhead, yielding an optimal Tunnel MTU of 1440 bytes, TCP MSS of 1400 bytes, and 93.33% payload efficiency.

Example Input
Physical WAN Interface MTU (Bytes)
1,500 Bytes
Outer Carrier IP Protocol Version
IPv4 Carrier (20-Byte Outer IP Header)
VPN Tunnel Protocol & Cipher Suite
WireGuard (ChaCha20-Poly1305 over UDP)
WAN Link Bandwidth Speed (Mbps)
100 Mbps
Calculated Output
Physical WAN Interface MTU
1,500 Bytes
Outer Carrier IP Header Size
20 Bytes
VPN Encapsulation & Cipher Overhead
40 Bytes
Total Tunnel Header Overhead per Packet
60 Bytes
Optimal VPN Tunnel Interface MTU
1,440 Bytes
Optimal TCP MSS Clamping Value
1,400 Bytes
Inner TCP Segment Payload Size
1,400 Bytes
Protocol Payload Transmission Efficiency
93.33 %
Effective Usable Payload Throughput
93.33 Mbps
Bandwidth Consumed by Encapsulation
6.67 Mbps
MTU & TCP MSS Clamping Rules (RouterOS & Linux)
# Konfigurasi Interface MTU & TCP MSS Clamping (MikroTik RouterOS v7 & Linux) /interface wireguard set [find] mtu=1440 /ip firewall mangle add chain=forward protocol=tcp tcp-flags=syn action=change-mss new-mss=1400 passthrough=yes comment="VPN MSS Clamping" # Linux iptables equivalent: iptables -t mangle -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --set-mss 1400
Overhead, MTU & Throughput Comparison Across VPN Protocols
VPN Protocol & CipherTunnel Encapsulation OverheadOptimal VPN Tunnel Interface MTUOptimal TCP MSS Clamping ValueEffective Usable Payload Throughput
WireGuard (UDP 8B + WG Header 32B + Poly1305 16B)60 Bytes1,440 Bytes1,400 Bytes93.33 Mbps
IPsec ESP AES-GCM Native (Proto 50)66 Bytes1,434 Bytes1,394 Bytes92.93 Mbps
IPsec ESP AES-GCM + UDP NAT-T (4500)74 Bytes1,426 Bytes1,386 Bytes92.4 Mbps
OpenVPN 2.6 Data Channel AEAD (UDP)68 Bytes1,432 Bytes1,392 Bytes92.8 Mbps
OpenVPN Data Channel (TCP)80 Bytes1,420 Bytes1,380 Bytes92 Mbps
GRE Tunnel (24B) + IPsec ESP NAT-T98 Bytes1,402 Bytes1,362 Bytes90.8 Mbps

Core Concept & Engineering Notes

Every Virtual Private Network (VPN) protocol encapsulates original inner IP packets inside outer transport, tunnel, and cryptographic authentication headers before transmitting them across a public WAN link. This encapsulation overhead reduces the maximum payload space available within a single physical network frame, lowering the effective Maximum Transmission Unit (MTU) of the virtual tunnel interface. If the tunnel MTU is not accurately aligned with the underlying WAN path MTU (such as 1500-byte standard Ethernet or 1492-byte PPPoE fiber), oversized packets suffer mid-flight IP fragmentation or silent drops when the Don't Fragment (DF) flag is set. Total encapsulation overhead varies by VPN protocol and outer IP family (20-byte IPv4 vs 40-byte IPv6). WireGuard employs fixed-size ChaCha20-Poly1305 AEAD framing over UDP, adding 20 bytes of outer IPv4 (or 40 bytes of IPv6) + 8 bytes UDP + 32 bytes WireGuard header/AEAD tag, resulting in 60 bytes of overhead on IPv4 (1440 MTU) or 80 bytes on IPv6 (1420 default MTU). Conversely, IPsec ESP operating over UDP NAT-Traversal (port 4500), OpenVPN, and GRE-over-IPsec introduce additional session headers, initialization vectors (IV), and cipher padding that consume 66 to 98 bytes per packet. To eliminate Path MTU Discovery (PMTUD) blackholes—where ICMP Fragmentation Needed packets are blocked by intermediate firewalls, causing HTTPS TLS handshakes and SSH sessions to stall—network engineers configure TCP MSS (Maximum Segment Size) clamping on border routers (MikroTik Mangle or Linux iptables). The optimal TCP MSS equals the Tunnel MTU minus 40 bytes (20-byte inner IPv4 header + 20-byte inner TCP header). Beyond preventing packet drops, protocol overhead directly governs effective usable throughput (goodput) and router CPU utilization. Every byte consumed by outer IP, UDP, ESP, or AEAD authentication headers reduces the ratio of application payload per physical frame. On 1492-byte PPPoE broadband links running multi-layered tunnels such as GRE over IPsec or OpenVPN over TCP, header overhead can consume nearly 8% to 10% of raw link capacity while risking TCP-over-TCP retransmission amplification. Calculating exact tunnel MTU and MSS boundaries ahead of deployment ensures maximum wire-speed efficiency across site-to-site and road-warrior VPN topologies.

How It Was Calculated (Formulas & Steps)

Frequently Asked Questions (FAQ)

Why does WireGuard default to an interface MTU of 1420 bytes?

WireGuard chooses 1420 bytes so a single tunnel configuration safely traverses both IPv4 (20-byte header) and IPv6 (40-byte header) carriers over a 1500-byte Ethernet link (1500 - 80 bytes = 1420 bytes).

What WireGuard MTU should be used when the ISP WAN link uses PPPoE (MTU 1492)?

Because PPPoE consumes 8 bytes and lowers the WAN MTU to 1492 bytes, the WireGuard MTU should be reduced to 1432 bytes (IPv4-only carrier) or 1412 bytes (IPv6-compatible), with a TCP MSS of 1392 or 1372 bytes.

What symptoms occur when the VPN MTU is too high and MSS clamping is missing?

Small ICMP pings succeed normally, but loading HTTPS websites, transferring files, or returning large SSH/SQL payloads hangs indefinitely because full-sized TCP segments with the DF bit set are dropped along the path.

Why is OpenVPN in TCP mode discouraged for site-to-site tunnels?

Beyond higher header overhead (60+ bytes), encapsulating inner TCP streams inside an outer TCP tunnel triggers TCP-over-TCP meltdown—where packet loss causes competing congestion backoff and duplicate retransmissions.

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References & Notes

Last updated: Technically Verified · Industry Standard

Note: Results above are mathematical estimates based on standard formulas. Always verify against official vendor documentation and site conditions before production deployment.

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🔬 Scientific Methodology & Normative Verification

Engineering Sensitivity Analysis, Response Curve & Technical Citation

✓ Calibrated to ISO/IEC/IEEE/TIA Clauses

1. 1. 3-Point Engineering Sensitivity & Tolerance Envelope

Comparative evaluation across theoretical laboratory bounds (0% loss), current nominal operating point, and conservative field safety bounds (±15% thermal/aging derating).

Evaluated Parameter Ideal Theoretical Bound Nominal Operating Point Conservative Safety Bound (±15%) Engineering Derating Rule
Physical WAN Interface MTU 1,350 1,500 1,725 Engineering Safety Margin (+15% Overhead)
Outer Carrier IP Header Size 18 20 23 Engineering Safety Margin (+15% Overhead)
VPN Encapsulation & Cipher Overhead 36 40 46 Engineering Safety Margin (+15% Overhead)
Total Tunnel Header Overhead per Packet 54 60 69 Engineering Safety Margin (+15% Overhead)
Optimal VPN Tunnel Interface MTU 1,296 1,440 1,656 Engineering Safety Margin (+15% Overhead)

2. 2. Mathematical Function Curve & Operating Coordinate (x₀, y₀)

MATHEMATICAL RESPONSE CURVE: PHYSICAL WAN INTERFACE MTU VS PHYSICAL WAN INTERFACE MTU Conservative Engineering Bound (+15% Safety Margin) 600 900 1,200 1,500 1,800 2,100 2,400 (x₀=1,500, y₀=1,500) Variabel Independen (x): Physical WAN Interface MTU

3. 3. Physical Constants & Normative Standard Clauses

R_hash(Offline) = 100000000000 guesses/s NIST SP 800-63B

Offline Multi-GPU Cluster Hash Rate Benchmark

Section 5.1.1.2 Memorized Secret Verifiers — Order-of-magnitude 10¹¹ guesses/sec benchmark for evaluating lower-bound password entropy resistance against offline attacks.

k_IEC(10¹²/2⁴⁰) = 0.9094947 TiB/TB ISO/IEC 80000-13:2008

Decimal Terabyte (SI) to Binary Tebibyte (IEC) Conversion Ratio

Clause 4 — Binary Prefixes — 1 TB = 10¹² Bytes; 1 TiB = 2⁴⁰ Bytes = 1,099,511,627,776 Bytes.

4. 4. Independent Technical & Academic Citation (IEEE / APA 7th / BibTeX / LaTeX)

Use the standard citation formats below to reference this computational methodology in engineering specifications, audit reports, or academic papers.

Format IEEE & APA 7th Edition

[IEEE] KalkuNet Engineering Team, "VPN Encryption Overhead & Tunnel MTU Calculator (WireGuard, IPsec, OpenVPN) — Standard Engineering Computational Instrument," KalkuNet Technical Suite, 2026. [Online]. Available: https://kalkunet.com/en/tools/vpn-encryption-overhead-calculator. [Accessed: 2026-11-08].

[APA 7th] KalkuNet Engineering Team. (2026). VPN Encryption Overhead & Tunnel MTU Calculator (WireGuard, IPsec, OpenVPN) (Production release 2026-11-08) [Engineering computational software]. KalkuNet. https://kalkunet.com/en/tools/vpn-encryption-overhead-calculator

BibTeX & LaTeX Derivation Snippet
@software{kalkunet_vpn_encryption_overhead_calculator_2026,
  author = {{KalkuNet Engineering Team}},
  title = {{VPN Encryption Overhead & Tunnel MTU Calculator (WireGuard, IPsec, OpenVPN) --- KalkuNet Engineering Suite}},
  year = {2026},
  publisher = {KalkuNet.com},
  url = {https://kalkunet.com/en/tools/vpn-encryption-overhead-calculator},
  urldate = {2026-11-08}
}

% LaTeX Engineering Derivation — Generated via https://kalkunet.com/en/tools/vpn-encryption-overhead-calculator
\begin{equation}
  \text{Model: } Total Tunnel Overhead = Outer_IP_Header (20B/40B) + VPN_Encapsulation_&_AEAD_Tag_Bytes
\end{equation}
% Parameter Input Terukur: physicalWanMtu = 1500, \; ipVersion = ipv4, \; vpnProtocol = wireguard, \; linkSpeedMbps = 100
% Hasil Evaluasi Numerik : physicalWanMtu = \mathbf{1500}, \; outerIpHeaderBytes = \mathbf{20}, \; vpnEncapsulationBytes = \mathbf{40}