.. 标题：BFD 和 IP SLA 计时器计算器
.. slug：bfd-ip-sla-计算器
.. 日期: 2026-03-27 12:00:00 世界标准时间
..标签：网络、bfd、ip-sla、故障转移、计算器、工具
..类别：计算器
..链接：
.. 描述：根据 tx/rx 间隔和乘数计算 BFD 故障检测时间。比较 BFD 与 IP SLA 检测延迟以实现亚秒级故障转移规划。
..类型：文本
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</style>
<div class="calc-container">
<div class="calc-header">
<h2>BFD 和 IP SLA 计时器计算器</h2>
<p>计算 BFD 会话和 IP SLA 探测的故障检测时间。比较亚秒级与秒级故障转移选项。</p>
</div>
BFD部分
<div class="result-section">
<div class="section-header">BFD检测时间</div>
<div class="section-content">
<p style="font-size:13px;color:#666;margin-top:0">检测时间 = max(desired_min_tx, required_min_rx) × detector_mult</p>
<div class="input-row">
<div class="input-group">
<label>所需的最小发送间隔（毫秒）</label>
<input id="bfdTx" max="60000" min="50" type="number" value="300"/>
</div>
<div class="input-group">
<label>所需的最小接收间隔（毫秒）</label>
<input id="bfdRx" max="60000" min="50" type="number" value="300"/>
</div>
<div class="input-group">
<label>检测乘数</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()">计算BFD</button>
</div>
<div id="bfdResult" style="display:none;margin-top:15px"></div>
</div>
</div>
IP SLA 部分
<div class="result-section">
<div class="section-header">IP SLA 故障转移计时器</div>
<div class="section-content">
<div class="input-row">
<div class="input-group">
<label>IP SLA 频率</label>
<input id="slaFreq" max="604800" min="1" type="number" value="5"/>
</div>
<div class="input-group">
<label>阈值（连续失败）</label>
<input id="slaThresh" max="100" min="1" type="number" value="3"/>
</div>
<div class="input-group">
<label>每个探头的超时（毫秒）</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()">计算 IP SLA</button>
</div>
<div id="slaResult" style="display:none;margin-top:15px"></div>
</div>
</div>
比较部分
<div class="result-section">
<div class="section-header">BFD 与 IP SLA 比较</div>
<div class="section-content">
<div class="button-container" style="justify-content:flex-start;margin-top:0">
<button class="calc-button" onclick="calcCompare()">比较两者</button>
</div>
<div id="compareResult" style="display:none;margin-top:15px"></div>
</div>
</div>
静态预设表
<div class="result-section">
<div class="section-header">常用 BFD 定时器预设</div>
<div class="section-content">
<table>
<tr><th>轮廓</th><th>最小发送/接收（毫秒）</th><th>乘数</th><th>检测时间</th><th>使用案例</th></tr>
<tr><td>挑衅的</td><td>50</td><td>3</td><td><span class="badge badge-fast">150毫秒</span></td><td>数据中心、同子网对等点</td></tr>
<tr><td>均衡</td><td>300</td><td>3</td><td>900毫秒</td><td>大多数 WAN 链接</td></tr>
<tr><td>保守的</td><td>500</td><td>3</td><td>1500毫秒</td><td>高延迟 WAN、卫星</td></tr>
<tr><td>慢（无 BFD）</td><td colspan="2">不适用</td><td><span class="badge badge-slow">30–180 秒</span></td><td>BGP 抑制计时器回退</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>