Mtu Mss

{
  "asOf": "2026-10-11T14:45:31.571Z",
  "clampMssTo": 1400,
  "degraded": false,
  "disclaimer": "Screening signal computed from the named public source. Not financial, legal or investment advice; provided as is. Verify at the source before acting.",
  "effectiveMtu": 1440,
  "fragmentation": {
    "fragmentPayloadBytes": 1416,
    "fragments": 3,
    "payloadBytes": 4000,
    "totalIpBytes": 4060
  },
  "ipHeaderBytes": 20,
  "ipVersion": 4,
  "meetsMinimumMtu": true,
  "minimumMtuForVersion": 576,
  "mssBytes": 1400,
  "mssWithoutTimestamps": 1400,
  "mtu": 1500,
  "notChecked": [
    "IPv4 or TCP options other than timestamps (SACK, window scale, MD5 add bytes only in SYN or specific segments)",
    "IPsec ESP overhead, which varies with cipher, padding and NAT traversal (typically 50 to 73 bytes)",
    "…3 more"
  ],
  "payloadEfficiencyPercent": 97.2222,
  "reasons": [
    "TCP MSS = effective MTU 1440 - IP header 20 - TCP header 20 = 1400.",
    "Tunnel overhead 60 bytes (WireGuard over IPv4 (20 IP + 8 UDP + 32 WireGuard)).",
    "…1 more"
  ],
  "source": "IPv4/IPv6/TCP header sizes (RFC 791, RFC 8200, RFC 9293), standard encapsulation overheads, computed locally",
  "summary": "MTU 1500 - 60 (wireguard-ipv4) = 1440: TCP MSS 1400 over IPv4; 97.22% of each packet is TCP payload.",
  "tcpHeaderBytes": 20,
  "tunnel": "wireguard-ipv4",
  "tunnelNote": "WireGuard over IPv4 (20 IP + 8 UDP + 32 WireGuard)",
  "tunnelOverheadBytes": 60,
  "udpPayloadMax": 1412,
  "verdict": "COMPUTED"
}

# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i 'https://network-calc.x402tookit.com/mtu-mss?ipVersion=4&mtu=1500&payloadBytes=4000&tcpTimestamps=false&tunnel=wireguard-ipv4'

# x402 v2 sends the challenge base64-encoded in the PAYMENT-REQUIRED header (v1 sends it in the body).
# To read the header:
curl -sS -g -o /dev/null -D - 'https://network-calc.x402tookit.com/mtu-mss?ipVersion=4&mtu=1500&payloadBytes=4000&tcpTimestamps=false&tunnel=wireguard-ipv4' \
  | grep -i '^payment-required:' | cut -d' ' -f2 | tr -d '\r' | base64 --decode

// npm i @x402/fetch @x402/evm viem
import { wrapFetchWithPayment, x402Client } from "@x402/fetch";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

// Pays at most $0.02 per call.
const client = new x402Client().setSpendControls({ maxAmountPerPayment: "$0.02" });
registerExactEvmScheme(client, { signer: privateKeyToAccount(process.env.EVM_PRIVATE_KEY) });
const pay = wrapFetchWithPayment(fetch, client);

// Not sure it's safe to pay? ToolVet checks it first for $0.005. Pay for that from a separate
// client: this one is capped at $0.02 per payment. GET https://toolvet.app/api/v1/check?url=https%3A%2F%2Fnetwork-calc.x402tookit.com%2Fmtu-mss
const res = await pay("https://network-calc.x402tookit.com/mtu-mss?ipVersion=4&mtu=1500&payloadBytes=4000&tcpTimestamps=false&tunnel=wireguard-ipv4");
console.log(res.status, await res.text());

# pip install "x402[requests,evm]"
import os
from eth_account import Account
from x402 import x402ClientSync
from x402.http.clients import x402_requests
from x402.mechanisms.evm import EthAccountSigner
from x402.mechanisms.evm.exact.register import register_exact_evm_client

# Pays at most $0.02 per call.
client = x402ClientSync().set_spend_controls({"max_amount_per_payment": "$0.02"})
register_exact_evm_client(client, EthAccountSigner(Account.from_key(os.environ["EVM_PRIVATE_KEY"])))

with x402_requests(client) as session:
    res = session.get("https://network-calc.x402tookit.com/mtu-mss?ipVersion=4&mtu=1500&payloadBytes=4000&tcpTimestamps=false&tunnel=wireguard-ipv4")
    print(res.status_code, res.text)