..标题：缓冲区膨胀和 BDP 调整工具
.. slug：缓冲区膨胀-bdp-工具
.. 日期: 2026-03-27 12:00:00 世界标准时间
.. 标签：网络、tcp、bufferbloat、bdp、性能、计算器、工具
..类别：计算器
..链接：
.. 描述：计算带宽延迟积，检测缓冲区膨胀，并获取适合您的链路配置的 AQM 建议（fq_codel、CAKE、PIE）。
..类型：文本
<style>
.calc-container { max-width: 900px; margin: 20px auto; padding: 20px; }
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code { background: #f0f0f0; padding: 2px 5px; border-radius: 3px; font-size: 12px; }
</style>
<div class="calc-container">
<div class="calc-header">
<h2>缓冲区膨胀和 BDP 调整工具</h2>
<p>计算带宽延迟积、检测缓冲区膨胀情况并获取 AQM 建议。</p>
<div class="input-grid">
<div class="input-group">
<label>链路带宽 (Mbps)</label>
<input id="bwMbps" min="0.1" step="any" type="number" value="100"/>
</div>
<div class="input-group">
<label>往返时间（毫秒）</label>
<input id="rttMs" min="0.1" step="any" type="number" value="50"/>
</div>
<div class="input-group">
<label>当前缓冲区大小（毫秒，可选）</label>
<input id="bufMs" min="0" placeholder="0 = skip" step="any" type="number" value="500"/>
</div>
</div>
<div class="button-container">
<button class="calc-button" onclick="calcBdp()">计算</button>
</div>
</div>
<div class="result-section" id="bdpResultSection" style="display:none">
<div class="section-header">BDP 和缓冲区膨胀结果</div>
<div class="section-content">
<div id="bdpResult"></div>
</div>
</div>
<div class="result-section">
<div class="section-header">AQM 推荐指南</div>
<div class="section-content">
<table>
<tr><th>空气质量管理</th><th>最适合</th><th>Linux命令</th><th>笔记</th></tr>
<tr><td><strong>fq_codel</strong></td><td>通用、低延迟</td>
<td><code>tc qdisc add dev eth0 root fq_codel</code></td>
<td>许多发行版中的默认设置；流量公平排队+CoDel</td></tr>
<tr><td><strong>蛋糕</strong></td><td>家庭路由器、ISP 边缘</td>
<td><code>tc qdisc add dev eth0 root cake bandwidth 100Mbit</code></td>
<td>包括塑形；最适合带宽有限的链接</td></tr>
<tr><td><strong>馅饼</strong></td><td>电缆调制解调器、DOCSIS</td>
<td><code>tc qdisc add dev eth0 root pie</code></td>
<td>比例积分控制器增强型； IETF RFC 8033</td></tr>
</table>
</div>
</div>
<div class="result-section">
<div class="section-header">BDP 参考表</div>
<div class="section-content">
<table id="bdpRefTable">
<tr><th>带宽</th><th>实时传输时间10毫秒</th><th>实时传输时间50毫秒</th><th>实时传输时间100毫秒</th><th>实时传输时间300毫秒</th></tr>
</table>
</div>
</div>
</div>
<script>
const BW_ROWS = [1, 10, 100, 1000, 10000];
const RTT_COLS = [10, 50, 100, 300];

function bdpBytes(bwMbps, rttMs) {
    return (bwMbps * 1e6 / 8) * (rttMs / 1000);
}

function fmtBytes(b) {
    if (b >= 1e9) return (b/1e9).toFixed(2) + ' GB';
    if (b >= 1e6) return (b/1e6).toFixed(2) + ' MB';
    if (b >= 1e3) return (b/1e3).toFixed(1) + ' KB';
    return Math.round(b) + ' B';
}

// Build reference table
(function buildRefTable() {
    const table = document.getElementById('bdpRefTable');
    BW_ROWS.forEach(bw => {
        const tr = document.createElement('tr');
        const label = bw >= 1000 ? `${bw/1000} Gbps` : `${bw} Mbps`;
        tr.innerHTML = `<td><strong>${label}</strong></td>`;
        RTT_COLS.forEach(rtt => {
            const bytes = bdpBytes(bw, rtt);
            tr.innerHTML += `<td>${fmtBytes(bytes)}</td>`;
        });
        table.appendChild(tr);
    });
})();

function calcBdp() {
    const bw = parseFloat(document.getElementById('bwMbps').value);
    const rtt = parseFloat(document.getElementById('rttMs').value);
    const bufMs = parseFloat(document.getElementById('bufMs').value);
    const div = document.getElementById('bdpResult');
    const section = document.getElementById('bdpResultSection');
    section.style.display = 'block';
    div.style.display = 'block';
    if (isNaN(bw) || isNaN(rtt) || bw <= 0 || rtt <= 0) {
        div.innerHTML = '<div class="result-box"><strong style="color:red">Enter valid bandwidth (&gt; 0 Mbps) and RTT (&gt; 0 ms).</strong></div>';
        return;
    }
    const bdp = bdpBytes(bw, rtt);
    const bufBytes = !isNaN(bufMs) && bufMs > 0 ? bdpBytes(bw, bufMs) : null;
    const bufRatio = bufBytes ? bufBytes / bdp : null;
    const bloat = bufRatio !== null && bufRatio > 4;

    // AQM recommendation
    let aqmRec = 'fq_codel';
    let aqmReason = 'general-purpose, excellent for most scenarios';
    if (bw < 20) { aqmRec = 'CAKE'; aqmReason = 'low-bandwidth link — CAKE\'s shaping prevents queue buildup'; }
    else if (bufRatio && bufRatio > 10) { aqmRec = 'CAKE'; aqmReason = 'severe buffer bloat — CAKE + shaping will reclaim latency'; }

    let bloatHtml = '';
    if (bufBytes !== null) {
        const cls = bloat ? 'warn' : 'good';
        bloatHtml = `<div class="result-box ${cls}" style="margin-top:12px">
            <strong>Buffer analysis:</strong> ${fmtBytes(bufBytes)} buffer (${bufMs} ms at ${bw} Mbps)<br>
            <strong>Buffer / BDP ratio:</strong> ${bufRatio.toFixed(1)}&times;<br>
            ${bloat
                ? `<strong style="color:#b06000">Buffer bloat likely.</strong> Buffer is ${bufRatio.toFixed(1)}&times; the BDP. Latency under load may spike by ~${Math.round(bufMs - rtt)} ms.`
                : `<strong style="color:#155724">Buffer sizing looks reasonable.</strong> Buffer is ${bufRatio.toFixed(1)}&times; the BDP.`}
        </div>`;
    }

    div.innerHTML = `<div class="result-box">
        <div class="metric-grid">
            <div class="metric-card"><div class="val">${fmtBytes(bdp)}</div><div class="lbl">BDP (bandwidth × RTT / 8)</div></div>
            <div class="metric-card"><div class="val">${(bdp/1500).toFixed(0)}</div><div class="lbl">BDP in 1500-byte packets</div></div>
            <div class="metric-card"><div class="val">${bw} Mbps</div><div class="lbl">Link bandwidth</div></div>
            <div class="metric-card"><div class="val">${rtt} ms</div><div class="lbl">RTT</div></div>
        </div>
        <hr style="margin:12px 0;border-color:#c8dfff">
        <strong>AQM Recommendation:</strong> <code>${aqmRec}</code> — ${aqmReason}
    </div>${bloatHtml}`;
}
</script>