.. タイトル: BFD および IP SLA タイマー計算ツール
.. スラグ: bfd-ip-sla-calculator
.. 日付: 2026-03-27 12:00:00 UTC
.. タグ: ネットワーキング、BFD、IP-SLA、フェイルオーバー、電卓、ツール
.. カテゴリ: 電卓
..リンク:
.. 説明: tx/rx 間隔と乗数から BFD 障害検出時間を計算します。 1 秒未満のフェールオーバー計画について、BFD と IP SLA の検出遅延を比較します。
.. タイプ: テキスト
<style>
/* ── CANONICAL DESIGN SYSTEM ─────────────────────────────────────────────── */
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/* ── END CANONICAL ────────────────────────────────────────────────────────── */

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.section-content .input-group select {
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.compare-card h4 { margin-top: 0; color: #2d6a2d; }
@media (max-width: 600px) { .compare-grid { grid-template-columns: 1fr; } }
</style>
<div class="calc-container">
<div class="calc-header">
<h2>BFD および IP SLA タイマー計算ツール</h2>
<p>BFD セッションと IP SLA プローブの障害検出時間を計算します。 1 秒未満と 2 秒規模のフェイルオーバー オプションを比較します。</p>
</div>
BFDセクション
<div class="result-section">
<div class="section-header">BFD 検出時間</div>
<div class="section-content">
<p style="font-size:13px;color:#666;margin-top:0">検出時間 = max(desired_min_tx, required_min_rx) × detect_mult</p>
<div class="input-row">
<div class="input-group">
<label>希望する最小送信間隔 (ミリ秒)</label>
<input id="bfdTx" max="60000" min="50" type="number" value="300"/>
</div>
<div class="input-group">
<label>必要な最小 RX 間隔 (ミリ秒)</label>
<input id="bfdRx" max="60000" min="50" type="number" value="300"/>
</div>
<div class="input-group">
<label>乗数の検出</label>
<input id="bfdMult" max="255" min="2" type="number" value="3"/>
</div>
</div>
<div class="button-container" style="justify-content:flex-start;margin-top:12px">
<button class="calc-button" onclick="calcBfd()">BFDの計算</button>
</div>
<div id="bfdResult" style="display:none;margin-top:15px"></div>
</div>
</div>
IP SLA セクション
<div class="result-section">
<div class="section-header">IP SLA フェールオーバー タイマー</div>
<div class="section-content">
<div class="input-row">
<div class="input-group">
<label>IP SLA 周波数 (秒)</label>
<input id="slaFreq" max="604800" min="1" type="number" value="5"/>
</div>
<div class="input-group">
<label>しきい値（連続失敗）</label>
<input id="slaThresh" max="100" min="1" type="number" value="3"/>
</div>
<div class="input-group">
<label>プローブごとのタイムアウト (ミリ秒)</label>
<input id="slaTimeout" max="60000" min="100" type="number" value="2000"/>
</div>
</div>
<div class="button-container" style="justify-content:flex-start;margin-top:12px">
<button class="calc-button" onclick="calcSla()">IP SLA の計算</button>
</div>
<div id="slaResult" style="display:none;margin-top:15px"></div>
</div>
</div>
比較セクション
<div class="result-section">
<div class="section-header">BFD と IP SLA の比較</div>
<div class="section-content">
<div class="button-container" style="justify-content:flex-start;margin-top:0">
<button class="calc-button" onclick="calcCompare()">両方を比較する</button>
</div>
<div id="compareResult" style="display:none;margin-top:15px"></div>
</div>
</div>
静的プリセット表
<div class="result-section">
<div class="section-header">一般的な BFD タイマーのプリセット</div>
<div class="section-content">
<table>
<tr><th>プロフィール</th><th>最小送信/受信 (ミリ秒)</th><th>乗数</th><th>検出時間</th><th>使用事例</th></tr>
<tr><td>攻撃的</td><td>50</td><td>3</td><td><span class="badge badge-fast">150ミリ秒</span></td><td>データセンター、同じサブネットピア</td></tr>
<tr><td>バランスの取れた</td><td>300</td><td>3</td><td>900ミリ秒</td><td>ほとんどの WAN リンク</td></tr>
<tr><td>保守的</td><td>500</td><td>3</td><td>1500ミリ秒</td><td>高遅延 WAN、衛星</td></tr>
<tr><td>遅い (BFD なし)</td><td colspan="2">該当なし</td><td><span class="badge badge-slow">30～180秒</span></td><td>BGP ホールドダウン タイマー フォールバック</td></tr>
</table>
</div>
</div>
</div>
<script>
function calcBfd() {
    const tx = parseInt(document.getElementById('bfdTx').value);
    const rx = parseInt(document.getElementById('bfdRx').value);
    const mult = parseInt(document.getElementById('bfdMult').value);
    const div = document.getElementById('bfdResult');
    div.style.display = 'block';
    if (isNaN(tx) || isNaN(rx) || isNaN(mult) || tx < 50 || rx < 50 || mult < 2) {
        div.innerHTML = '<strong style="color:red">Invalid input. Min TX/RX &ge; 50 ms, multiplier &ge; 2.</strong>';
        return;
    }
    const negotiated = Math.max(tx, rx);
    const detectionMs = negotiated * mult;
    const sla = detectionMs < 500 ? 'sub-500ms — excellent for datacenter failover'
        : detectionMs < 1000 ? 'sub-second — suitable for most WAN failover'
        : detectionMs < 3000 ? 'multi-second — suitable for slow WAN/satellite'
        : 'slow — consider reducing intervals if link supports it';
    div.innerHTML = `
        <div class="result-box">
        <span class="result-highlight">${detectionMs} ms</span> detection time<br>
        <strong>Negotiated interval:</strong> ${negotiated} ms (max of TX ${tx} ms, RX ${rx} ms)<br>
        <strong>Multiplier:</strong> ${mult} missed hellos before failover<br>
        <strong>Assessment:</strong> ${sla}
        </div>`;
}

function calcSla() {
    const freq = parseInt(document.getElementById('slaFreq').value);
    const thresh = parseInt(document.getElementById('slaThresh').value);
    const timeout = parseInt(document.getElementById('slaTimeout').value);
    const div = document.getElementById('slaResult');
    div.style.display = 'block';
    if (isNaN(freq) || isNaN(thresh) || isNaN(timeout) || freq < 1 || thresh < 1 || timeout < 100) {
        div.innerHTML = '<strong style="color:red">Invalid input. Frequency &ge; 1 s, threshold &ge; 1, timeout &ge; 100 ms.</strong>';
        return;
    }
    const worstCaseMs = (freq * 1000 * thresh) + timeout;
    const bestCaseMs = (freq * 1000 * (thresh - 1)) + timeout;
    div.innerHTML = `
        <div class="result-box">
        <span class="result-highlight">${(worstCaseMs / 1000).toFixed(1)} s</span> worst-case detection<br>
        <strong>Best case:</strong> ${(bestCaseMs / 1000).toFixed(1)} s (failure occurs just after successful probe)<br>
        <strong>Worst case:</strong> ${(worstCaseMs / 1000).toFixed(1)} s (failure occurs just after failed probe starts)<br>
        <strong>Probe formula:</strong> (frequency &times; threshold) + timeout = (${freq}s &times; ${thresh}) + ${timeout}ms
        </div>`;
}

function calcCompare() {
    const tx = parseInt(document.getElementById('bfdTx').value) || 300;
    const rx = parseInt(document.getElementById('bfdRx').value) || 300;
    const mult = parseInt(document.getElementById('bfdMult').value) || 3;
    const freq = parseInt(document.getElementById('slaFreq').value) || 5;
    const thresh = parseInt(document.getElementById('slaThresh').value) || 3;
    const timeout = parseInt(document.getElementById('slaTimeout').value) || 2000;
    const bfdMs = Math.max(tx, rx) * mult;
    const slaMs = (freq * 1000 * thresh) + timeout;
    const div = document.getElementById('compareResult');
    div.style.display = 'block';
    const faster = bfdMs < slaMs ? 'BFD' : 'IP SLA';
    const ratio = (Math.max(bfdMs, slaMs) / Math.min(bfdMs, slaMs)).toFixed(1);
    div.innerHTML = `<div class="compare-grid">
        <div class="compare-card">
            <h4>BFD</h4>
            <div class="result-highlight">${bfdMs} ms</div>
            <div>Negotiated: ${Math.max(tx, rx)} ms &times; ${mult}</div>
        </div>
        <div class="compare-card">
            <h4>IP SLA</h4>
            <div class="result-highlight">${(slaMs / 1000).toFixed(1)} s</div>
            <div>Worst case: ${freq}s &times; ${thresh} + ${timeout}ms</div>
        </div>
    </div>
    <div class="result-box" style="margin-top:12px">
        <strong>${faster} is faster</strong> by ${ratio}&times; in this configuration.<br>
        ${bfdMs < 1000 ? '<em>BFD at this setting provides sub-second failover not achievable with IP SLA at standard frequencies.</em>' : ''}
    </div>`;
}
</script>