.. titel: BFD & IP SLA Timer Calculator
.. slug: bfd-ip-sla-lommeregner
.. dato: 27-03-2026 12:00:00 UTC
.. tags: netværk, bfd, ip-sla, failover, lommeregner, værktøj
.. kategori: Lommeregnere
.. link:
.. beskrivelse: Beregn BFD-fejldetektionstid ud fra tx/rx-intervaller og multiplikator. Sammenlign BFD vs IP SLA-detektionsforsinkelse for sub-sekund failover-planlægning.
.. type: tekst
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</style>
<div class="calc-container">
<div class="calc-header">
<h2>BFD &amp; IP SLA Timer Lommeregner</h2>
<p>Beregn fejldetektionstid for BFD-sessioner og IP SLA-sonder. Sammenlign muligheder for failover i sub-sekund vs. anden-skala.</p>
</div>
BFD sektion
<div class="result-section">
<div class="section-header">BFD-detektionstid</div>
<div class="section-content">
<p style="font-size:13px;color:#666;margin-top:0">Detektionstid = max(desired_min_tx, required_min_rx) × detect_mult</p>
<div class="input-row">
<div class="input-group">
<label>Ønsket min. TX-interval (ms)</label>
<input id="bfdTx" max="60000" min="50" type="number" value="300"/>
</div>
<div class="input-group">
<label>Påkrævet min. RX-interval (ms)</label>
<input id="bfdRx" max="60000" min="50" type="number" value="300"/>
</div>
<div class="input-group">
<label>Opdag multiplikator</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()">Beregn BFD</button>
</div>
<div id="bfdResult" style="display:none;margin-top:15px"></div>
</div>
</div>
IP SLA sektion
<div class="result-section">
<div class="section-header">IP SLA Failover Timer</div>
<div class="section-content">
<div class="input-row">
<div class="input-group">
<label>IP SLA-frekvens(er)</label>
<input id="slaFreq" max="604800" min="1" type="number" value="5"/>
</div>
<div class="input-group">
<label>Tærskel (på hinanden følgende fejl)</label>
<input id="slaThresh" max="100" min="1" type="number" value="3"/>
</div>
<div class="input-group">
<label>Timeout pr. sonde (ms)</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()">Beregn IP SLA</button>
</div>
<div id="slaResult" style="display:none;margin-top:15px"></div>
</div>
</div>
Sammenligningsafsnit
<div class="result-section">
<div class="section-header">BFD vs IP SLA sammenligning</div>
<div class="section-content">
<div class="button-container" style="justify-content:flex-start;margin-top:0">
<button class="calc-button" onclick="calcCompare()">Sammenlign begge</button>
</div>
<div id="compareResult" style="display:none;margin-top:15px"></div>
</div>
</div>
Statisk forudindstillingstabel
<div class="result-section">
<div class="section-header">Almindelige BFD-timerforudindstillinger</div>
<div class="section-content">
<table>
<tr><th>Profil</th><th>Min TX/RX (ms)</th><th>Multiplikator</th><th>Detektionstid</th><th>Use Case</th></tr>
<tr><td>Aggressiv</td><td>50</td><td>3</td><td><span class="badge badge-fast">150 ms</span></td><td>Datacenter, peers med samme undernet</td></tr>
<tr><td>Balanceret</td><td>300</td><td>3</td><td>900 ms</td><td>De fleste WAN-links</td></tr>
<tr><td>Konservativ</td><td>500</td><td>3</td><td>1500 ms</td><td>Høj latens WAN, satellit</td></tr>
<tr><td>Langsom (ingen BFD)</td><td colspan="2">N/A</td><td><span class="badge badge-slow">30-180 sek</span></td><td>BGP hold-down timer fallback</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>