.. title: Linux TCP Sysctl チューニング リファレンス
..スラッグ: linux-tcp-sysctl-reference
.. 日付: 2026-03-27 12:00:00 UTC
.. タグ: Linux、TCP、sysctl、パフォーマンス、カーネル、電卓、ツール
.. カテゴリ: 電卓
..リンク:
.. 説明: Interactive Linux net.ipv4.tcp_* および net.core.* パラメーター ガイド。バルク転送、遅延に敏感な RPC、高接続 Web サーバー、およびロングファット パイプ WAN 用のワークロード プリセットが含まれています。
.. タイプ: テキスト
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<div class="calc-container">
<div class="calc-header">
<h2>Linux TCP Sysctl チューニング リファレンス</h2>
<p>相互の作用<code style="color:rgba(255,255,255,0.9)">net.ipv4.tcp_*</code>そして<code style="color:rgba(255,255,255,0.9)">net.core.*</code>パラメータ ガイドには、バルク転送、遅延に敏感な RPC、高接続 Web サーバー、およびロング ファット パイプ WAN 用のワークロード プリセットが含まれています。</p>
<div class="input-grid">
<div class="input-group">
<label>検索/フィルター</label>
<input id="searchInput" oninput="filterParams(this.value)" placeholder="Search parameters..." type="text"/>
</div>
<div class="input-group">
<label>ワークロードのプリセット</label>
<div class="preset-row" id="presetRow"></div>
</div>
</div>
</div>
<div class="result-section">
<div class="section-header">TCP Sysctl パラメータ</div>
<div class="section-content" id="paramList">
</div>
<div style="padding: 20px; background: #fafafa; border-top: 1px solid #e0e0e0;">
<button class="copy-all-btn" onclick="copyAll()">表示されているすべてのパラメータを sysctl コマンドとしてコピー</button>
</div>
</div>
</div>
<script>
const PARAMS = [
    {
        name: 'net.ipv4.tcp_rmem',
        desc: 'TCP receive buffer sizes: min, default, max (bytes). Kernel auto-tunes between min and max.',
        default: '4096 131072 6291456',
        presets: {
            bulk: '4096 131072 134217728',
            rpc: '4096 87380 4194304',
            web: '4096 131072 16777216',
            wan: '4096 131072 134217728',
        },
        range: 'min 4096; max up to ~1GB (limited by net.core.rmem_max)',
        tags: ['buffer', 'receive', 'window'],
        doc: 'https://www.kernel.org/doc/html/latest/networking/ip-sysctl.html',
    },
    {
        name: 'net.ipv4.tcp_wmem',
        desc: 'TCP send buffer sizes: min, default, max (bytes).',
        default: '4096 16384 4194304',
        presets: {
            bulk: '4096 16384 134217728',
            rpc: '4096 16384 4194304',
            web: '4096 16384 16777216',
            wan: '4096 16384 134217728',
        },
        range: 'min 4096; max up to ~1GB',
        tags: ['buffer', 'send', 'window'],
        doc: 'https://www.kernel.org/doc/html/latest/networking/ip-sysctl.html',
    },
    {
        name: 'net.core.rmem_max',
        desc: 'Maximum receive socket buffer size. Upper bound for tcp_rmem max.',
        default: '212992',
        presets: {
            bulk: '134217728',
            rpc: '4194304',
            web: '16777216',
            wan: '134217728',
        },
        range: '212992 – 2147483647',
        tags: ['buffer', 'receive', 'core'],
        doc: 'https://www.kernel.org/doc/html/latest/networking/ip-sysctl.html',
    },
    {
        name: 'net.core.wmem_max',
        desc: 'Maximum send socket buffer size.',
        default: '212992',
        presets: {
            bulk: '134217728',
            rpc: '4194304',
            web: '16777216',
            wan: '134217728',
        },
        range: '212992 – 2147483647',
        tags: ['buffer', 'send', 'core'],
        doc: 'https://www.kernel.org/doc/html/latest/networking/ip-sysctl.html',
    },
    {
        name: 'net.ipv4.tcp_congestion_control',
        desc: 'Default TCP congestion control algorithm.',
        default: 'cubic',
        presets: {
            bulk: 'bbr',
            rpc: 'cubic',
            web: 'bbr',
            wan: 'bbr',
        },
        range: 'cubic, bbr, reno, htcp (check: sysctl net.ipv4.tcp_available_congestion_control)',
        tags: ['congestion', 'bbr', 'cubic'],
        doc: 'https://www.kernel.org/doc/html/latest/networking/ip-sysctl.html',
    },
    {
        name: 'net.ipv4.tcp_window_scaling',
        desc: 'Enable TCP window scaling (RFC 1323). Required for windows > 65535 bytes.',
        default: '1',
        presets: { bulk: '1', rpc: '1', web: '1', wan: '1' },
        range: '0 (disable) or 1 (enable)',
        tags: ['window', 'rfc1323'],
        doc: 'https://www.kernel.org/doc/html/latest/networking/ip-sysctl.html',
    },
    {
        name: 'net.ipv4.tcp_timestamps',
        desc: 'RFC 1323 timestamps — used for PAWS (protection against wrapped sequence numbers) and RTT measurement.',
        default: '1',
        presets: { bulk: '1', rpc: '1', web: '1', wan: '1' },
        range: '0 (disable), 1 (enable), 2 (enable without ECR)',
        tags: ['rfc1323', 'paws', 'rtt'],
        doc: 'https://www.kernel.org/doc/html/latest/networking/ip-sysctl.html',
    },
    {
        name: 'net.ipv4.tcp_sack',
        desc: 'Selective Acknowledgements (RFC 2018). Allows receiver to inform sender of non-contiguous received segments, improving recovery from multiple losses.',
        default: '1',
        presets: { bulk: '1', rpc: '1', web: '1', wan: '1' },
        range: '0 or 1',
        tags: ['sack', 'loss', 'recovery'],
        doc: 'https://www.kernel.org/doc/html/latest/networking/ip-sysctl.html',
    },
    {
        name: 'net.ipv4.tcp_max_syn_backlog',
        desc: 'Maximum number of SYN packets queued per listening socket before dropping. Increase for high connection-rate servers.',
        default: '1024',
        presets: {
            bulk: '1024',
            rpc: '4096',
            web: '65536',
            wan: '1024',
        },
        range: '128 – 65536 (limited by system memory)',
        tags: ['syn', 'connection', 'backlog'],
        doc: 'https://www.kernel.org/doc/html/latest/networking/ip-sysctl.html',
    },
    {
        name: 'net.core.somaxconn',
        desc: 'Maximum socket listen backlog (accept queue depth). Application must also set listen() backlog >= this value.',
        default: '4096',
        presets: {
            bulk: '4096',
            rpc: '8192',
            web: '65535',
            wan: '4096',
        },
        range: '128 – 65535',
        tags: ['connection', 'backlog', 'accept', 'core'],
        doc: 'https://www.kernel.org/doc/html/latest/networking/ip-sysctl.html',
    },
    {
        name: 'net.ipv4.tcp_tw_reuse',
        desc: 'Allow reuse of TIME_WAIT sockets for new connections when safe (requires timestamps). Reduces port exhaustion under heavy connection churn.',
        default: '2',
        presets: {
            bulk: '2',
            rpc: '1',
            web: '1',
            wan: '2',
        },
        range: '0 (disable), 1 (enable for loopback), 2 (enable for all)',
        tags: ['time_wait', 'port', 'reuse'],
        doc: 'https://www.kernel.org/doc/html/latest/networking/ip-sysctl.html',
    },
    {
        name: 'net.ipv4.tcp_fin_timeout',
        desc: 'Time (seconds) a socket stays in FIN_WAIT_2 state before being forcibly closed. Reduce to reclaim ports faster under high connection rates.',
        default: '60',
        presets: {
            bulk: '60',
            rpc: '15',
            web: '15',
            wan: '60',
        },
        range: '5 – 120 seconds',
        tags: ['fin', 'timeout', 'connection'],
        doc: 'https://www.kernel.org/doc/html/latest/networking/ip-sysctl.html',
    },
];

const PRESETS = {
    default: { label: 'Kernel Defaults', desc: 'Show kernel default values' },
    bulk: { label: 'Bulk File Transfer', desc: 'Large BDP, maximize throughput over high-RTT links' },
    rpc: { label: 'Latency-Sensitive RPC', desc: 'Low-latency datacenter RPCs (Redis, gRPC, etc.)' },
    web: { label: 'High-Connection Web Server', desc: 'High connection rate, many short-lived connections' },
    wan: { label: 'Long-Fat-Pipe WAN', desc: 'High bandwidth × high RTT (satellite, cross-continental)' },
};

let currentPreset = 'default';
let searchQuery = '';

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        btn.title = p.desc;
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    renderParams();
}

function setPreset(key) {
    currentPreset = key;
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}

function filterParams(q) {
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    renderParams();
}

function getVal(p) {
    return currentPreset === 'default' ? p.default : (p.presets[currentPreset] || p.default);
}

function renderParams() {
    const list = document.getElementById('paramList');
    const filtered = PARAMS.filter(p => {
        if (!searchQuery) return true;
        return p.name.toLowerCase().includes(searchQuery) ||
               p.desc.toLowerCase().includes(searchQuery) ||
               p.tags.some(t => t.includes(searchQuery));
    });

    if (!filtered.length) {
        list.innerHTML = '<p style="color:#999">No parameters match your filter.</p>';
        return;
    }

    list.innerHTML = filtered.map((p, idx) => {
        const val = getVal(p);
        const cmd = `sysctl -w ${p.name}=${val}`;
        const tags = p.tags.map(t => `<span class="param-tag">${t}</span>`).join('');
        const changed = currentPreset !== 'default' && val !== p.default;
        return `<div class="param-card">
            <div class="param-header" onclick="toggleCard(event)">
                <span class="param-name">${p.name}</span>
                <span class="param-value" ${changed ? 'style="background:#d4edda;color:#155724"' : ''}>${val}</span>
            </div>
            <div class="param-body">
                ${p.desc}
                <div class="param-meta">
                    <span><strong>Default:</strong> ${p.default}</span>
                    <span><strong>Range:</strong> ${p.range}</span>
                </div>
                <div style="margin-top:8px">${tags}</div>
                <div class="copy-block">${cmd} <button class="copy-btn" onclick="copyCmd('${cmd}')">Copy</button></div>
            </div>
        </div>`;
    }).join('');
}

function copyCmd(cmd) {
    navigator.clipboard.writeText(cmd).catch(() => {
        const ta = document.createElement('textarea');
        ta.value = cmd; document.body.appendChild(ta); ta.select(); document.execCommand('copy'); ta.remove();
    });
}

function copyAll() {
    const filtered = PARAMS.filter(p => {
        if (!searchQuery) return true;
        return p.name.toLowerCase().includes(searchQuery) || p.desc.toLowerCase().includes(searchQuery) || p.tags.some(t => t.includes(searchQuery));
    });
    const cmds = filtered.map(p => `sysctl -w ${p.name}=${getVal(p)}`).join('\n');
    copyCmd(cmds);
    alert(`Copied ${filtered.length} sysctl commands to clipboard.`);
}

function toggleCard(event) {
    const card = event.currentTarget.closest('.param-card');
    const body = card.querySelector('.param-body');
    body.classList.toggle('open');
}

init();
</script>