.. naslov: Vizualizator glave paketa
.. polž: vizualizator paketov
.. datum: 2026-01-23 12:00:00 UTC
.. oznake: mreženje, kalkulator, orodje, paket, enkapsulacija, mtu, mss
.. kategorija:
.. povezava:
.. opis: Vizualizirajte glave omrežnih paketov in stroške enkapsulacije, da boste razumeli vpliv tovora
.. vrsta: besedilo
<style>
    .packet-viz-container {
        max-width: 1200px;
        margin: 20px auto;
        padding: 20px;
    }

    .calc-header {
        margin-bottom: 30px;
        padding: 25px;
        background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
        border-radius: 12px;
        box-shadow: 0 4px 6px rgba(0,0,0,0.1);
        color: white;
    }

    .calc-header h2 {
        margin-top: 0;
        color: white;
        font-size: 28px;
        margin-bottom: 10px;
    }

    .calc-header p {
        margin: 10px 0 20px 0;
        opacity: 0.95;
        font-size: 15px;
        line-height: 1.6;
    }

    .config-grid {
        display: grid;
        grid-template-columns: 1fr 1fr;
        gap: 20px;
    }

    .config-panel {
        background: rgba(255,255,255,0.1);
        padding: 15px;
        border-radius: 8px;
    }

    .config-panel h4 {
        margin: 0 0 12px 0;
        color: white;
        font-size: 14px;
        text-transform: uppercase;
        letter-spacing: 0.5px;
    }

    .input-row {
        display: flex;
        gap: 10px;
        margin-bottom: 12px;
    }

    .input-group {
        flex: 1;
        display: flex;
        flex-direction: column;
    }

    .input-group label {
        font-weight: bold;
        color: white;
        margin-bottom: 6px;
        font-size: 13px;
    }

    .input-group input,
    .input-group select {
        padding: 10px 12px;
        font-size: 14px;
        border: 2px solid rgba(255,255,255,0.3);
        border-radius: 6px;
        background: rgba(255,255,255,0.95);
        transition: all 0.3s ease;
    }

    .input-group input:focus,
    .input-group select:focus {
        outline: none;
        border-color: #4CAF50;
        background: white;
        box-shadow: 0 0 0 3px rgba(76, 175, 80, 0.2);
    }

    /* Stack Builder Styles */
    .stack-builder {
        margin-top: 15px;
    }

    .add-header-row {
        display: flex;
        gap: 10px;
        margin-bottom: 15px;
    }

    .add-header-row select {
        flex: 1;
        padding: 10px 12px;
        font-size: 14px;
        border: 2px solid rgba(255,255,255,0.3);
        border-radius: 6px;
        background: rgba(255,255,255,0.95);
    }

    .add-btn {
        padding: 10px 20px;
        font-size: 14px;
        background: #4CAF50;
        color: white;
        border: none;
        border-radius: 6px;
        cursor: pointer;
        font-weight: bold;
        transition: all 0.2s ease;
    }

    .add-btn:hover {
        background: #45a049;
        transform: translateY(-1px);
    }

    .tunnel-shortcuts {
        display: flex;
        flex-wrap: wrap;
        gap: 8px;
        margin-bottom: 15px;
    }

    .tunnel-shortcut-btn {
        padding: 6px 12px;
        font-size: 11px;
        background: rgba(255,255,255,0.2);
        color: white;
        border: 1px solid rgba(255,255,255,0.3);
        border-radius: 15px;
        cursor: pointer;
        transition: all 0.2s ease;
    }

    .tunnel-shortcut-btn:hover {
        background: rgba(255,255,255,0.3);
    }

    .header-stack {
        background: rgba(0,0,0,0.2);
        border-radius: 8px;
        padding: 10px;
        min-height: 200px;
        max-height: 400px;
        overflow-y: auto;
    }

    .stack-empty {
        color: rgba(255,255,255,0.5);
        text-align: center;
        padding: 40px;
        font-style: italic;
    }

    .stack-item {
        display: flex;
        align-items: center;
        gap: 10px;
        padding: 10px 12px;
        margin-bottom: 6px;
        background: rgba(255,255,255,0.95);
        border-radius: 6px;
        transition: all 0.2s ease;
        cursor: grab;
    }

    .stack-item:hover {
        background: white;
        box-shadow: 0 2px 8px rgba(0,0,0,0.15);
    }

    .stack-item.dragging {
        opacity: 0.5;
        cursor: grabbing;
    }

    .stack-item .item-number {
        width: 24px;
        height: 24px;
        background: #667eea;
        color: white;
        border-radius: 50%;
        display: flex;
        align-items: center;
        justify-content: center;
        font-size: 12px;
        font-weight: bold;
        flex-shrink: 0;
    }

    .stack-item .item-color {
        width: 16px;
        height: 16px;
        border-radius: 3px;
        flex-shrink: 0;
    }

    .stack-item .item-name {
        flex: 1;
        font-weight: 500;
        color: #333;
    }

    .stack-item .item-layer {
        font-size: 11px;
        padding: 2px 8px;
        background: #e0e0e0;
        border-radius: 10px;
        color: #666;
    }

    .stack-item .item-size {
        font-family: 'Courier New', monospace;
        font-size: 13px;
        color: #666;
        min-width: 45px;
        text-align: right;
    }

    .stack-item .item-delete {
        width: 24px;
        height: 24px;
        background: #f44336;
        color: white;
        border: none;
        border-radius: 4px;
        cursor: pointer;
        display: flex;
        align-items: center;
        justify-content: center;
        font-size: 14px;
        transition: all 0.2s ease;
        flex-shrink: 0;
    }

    .stack-item .item-delete:hover {
        background: #d32f2f;
        transform: scale(1.1);
    }

    .stack-summary {
        margin-top: 10px;
        padding: 10px;
        background: rgba(255,255,255,0.1);
        border-radius: 6px;
        font-size: 13px;
        color: white;
    }

    .stack-summary span {
        margin-right: 20px;
    }

    .stack-summary strong {
        color: #4CAF50;
    }

    .preset-section {
        margin-top: 15px;
    }

    .preset-buttons {
        display: flex;
        flex-wrap: wrap;
        gap: 8px;
    }

    .preset-btn {
        padding: 8px 14px;
        font-size: 12px;
        background: rgba(255,255,255,0.2);
        color: white;
        border: 1px solid rgba(255,255,255,0.3);
        border-radius: 20px;
        cursor: pointer;
        transition: all 0.2s ease;
    }

    .preset-btn:hover {
        background: rgba(255,255,255,0.3);
        transform: translateY(-1px);
    }

    .preset-btn.active {
        background: #4CAF50;
        border-color: #4CAF50;
    }

    .calc-button {
        padding: 14px 35px;
        font-size: 16px;
        background: #4CAF50;
        color: white;
        border: none;
        border-radius: 6px;
        cursor: pointer;
        font-weight: bold;
        transition: all 0.3s ease;
        box-shadow: 0 2px 4px rgba(0,0,0,0.2);
        width: 100%;
        margin-top: 20px;
    }

    .calc-button:hover {
        background: #45a049;
        transform: translateY(-1px);
        box-shadow: 0 4px 8px rgba(0,0,0,0.3);
    }

    /* Results Section */
    .results-section {
        margin-top: 30px;
    }

    .summary-cards {
        display: grid;
        grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
        gap: 15px;
        margin-bottom: 20px;
    }

    .summary-card {
        background: white;
        border-radius: 8px;
        padding: 20px;
        text-align: center;
        box-shadow: 0 2px 4px rgba(0,0,0,0.05);
        border-top: 4px solid #4CAF50;
        transition: all 0.3s ease;
    }

    .summary-card:hover {
        transform: translateY(-2px);
        box-shadow: 0 4px 8px rgba(0,0,0,0.1);
    }

    .summary-card.warning {
        border-top-color: #ff9800;
    }

    .summary-card.danger {
        border-top-color: #f44336;
    }

    .summary-card .card-label {
        font-size: 12px;
        color: #666;
        text-transform: uppercase;
        letter-spacing: 0.5px;
        margin-bottom: 8px;
    }

    .summary-card .card-value {
        font-size: 28px;
        font-weight: bold;
        color: #333;
        font-family: 'Courier New', monospace;
    }

    .summary-card .card-unit {
        font-size: 14px;
        color: #666;
        margin-left: 4px;
    }

    .summary-card .card-subtext {
        font-size: 11px;
        color: #888;
        margin-top: 5px;
    }

    .visualization-panel {
        background: white;
        border: 1px solid #e0e0e0;
        border-radius: 8px;
        overflow: hidden;
        box-shadow: 0 2px 4px rgba(0,0,0,0.05);
        margin-bottom: 20px;
    }

    .panel-header {
        background: linear-gradient(135deg, #4CAF50 0%, #45a049 100%);
        color: white;
        padding: 15px 20px;
        font-weight: bold;
        font-size: 16px;
        display: flex;
        justify-content: space-between;
        align-items: center;
    }

    .panel-content {
        padding: 20px;
        background: #fafafa;
    }

    .byte-grid-container {
        overflow-x: auto;
        padding: 10px 0;
    }

    #byteGrid {
        display: block;
        margin: 0 auto;
    }

    .legend {
        display: flex;
        flex-wrap: wrap;
        gap: 15px;
        margin-top: 15px;
        padding: 15px;
        background: white;
        border-radius: 6px;
    }

    .legend-item {
        display: flex;
        align-items: center;
        gap: 8px;
        font-size: 13px;
    }

    .legend-color {
        width: 20px;
        height: 20px;
        border-radius: 4px;
        border: 1px solid rgba(0,0,0,0.1);
    }

    .header-breakdown {
        background: white;
        border: 1px solid #e0e0e0;
        border-radius: 8px;
        overflow: hidden;
        margin-bottom: 20px;
    }

    .breakdown-table {
        width: 100%;
        border-collapse: collapse;
    }

    .breakdown-table th,
    .breakdown-table td {
        padding: 12px 15px;
        text-align: left;
        border-bottom: 1px solid #e0e0e0;
    }

    .breakdown-table th {
        background: #f5f5f5;
        font-weight: bold;
        color: #555;
        font-size: 13px;
        text-transform: uppercase;
    }

    .breakdown-table tr:last-child td {
        border-bottom: none;
    }

    .breakdown-table tr:hover td {
        background: #f9f9f9;
    }

    .breakdown-table .layer-badge {
        display: inline-block;
        padding: 3px 8px;
        border-radius: 12px;
        font-size: 11px;
        font-weight: bold;
        color: white;
    }

    .layer-l2 { background: #2196F3; }
    .layer-l25 { background: #00BCD4; }
    .layer-l3 { background: #4CAF50; }
    .layer-l4 { background: #FF9800; }
    .layer-tunnel { background: #9C27B0; }
    .layer-payload { background: #607D8B; }

    .byte-range {
        font-family: 'Courier New', monospace;
        font-size: 12px;
        color: #666;
    }

    .warnings-panel {
        background: #fff3e0;
        border: 1px solid #ff9800;
        border-radius: 8px;
        padding: 15px;
        margin-bottom: 20px;
    }

    .warnings-panel h4 {
        margin: 0 0 10px 0;
        color: #e65100;
        font-size: 14px;
    }

    .warning-item {
        padding: 8px 12px;
        background: rgba(255, 152, 0, 0.1);
        border-radius: 4px;
        margin-bottom: 8px;
        font-size: 13px;
        color: #e65100;
    }

    .warning-item:last-child {
        margin-bottom: 0;
    }

    .mss-recommendation {
        background: #e3f2fd;
        border: 1px solid #2196F3;
        border-radius: 8px;
        padding: 15px 20px;
        margin-top: 20px;
    }

    .mss-recommendation h4 {
        margin: 0 0 10px 0;
        color: #1565c0;
        font-size: 14px;
    }

    .mss-recommendation p {
        margin: 0;
        color: #0d47a1;
        font-size: 14px;
        line-height: 1.6;
    }

    .mss-recommendation code {
        background: rgba(33, 150, 243, 0.1);
        padding: 2px 6px;
        border-radius: 3px;
        font-family: 'Courier New', monospace;
    }

    .description-section {
        margin-top: 30px;
        padding: 20px;
        background: white;
        border-radius: 8px;
        box-shadow: 0 2px 4px rgba(0,0,0,0.05);
        border-top: 3px solid #4CAF50;
    }

    .description-section h3 {
        color: #4CAF50;
        margin-top: 0;
    }

    .description-section p {
        line-height: 1.6;
        color: #555;
        margin-bottom: 15px;
    }

    .description-section ul {
        line-height: 1.8;
        color: #555;
    }

    .tooltip {
        position: absolute;
        background: rgba(0,0,0,0.9);
        color: white;
        padding: 10px 14px;
        border-radius: 6px;
        font-size: 12px;
        pointer-events: none;
        z-index: 1000;
        max-width: 250px;
        box-shadow: 0 4px 12px rgba(0,0,0,0.3);
    }

    .tooltip .tooltip-header {
        font-weight: bold;
        margin-bottom: 5px;
        color: #4CAF50;
    }

    .tooltip .tooltip-detail {
        color: #ccc;
        font-family: 'Courier New', monospace;
    }

    @media (max-width: 900px) {
        .config-grid {
            grid-template-columns: 1fr;
        }

        .summary-cards {
            grid-template-columns: 1fr 1fr;
        }

        .input-row {
            flex-direction: column;
        }
    }
</style>
<div class="packet-viz-container">
<div class="calc-header">
<h2>Vizualizator glave paketa</h2>
<p>Vizualizirajte vpliv enkapsulacije omrežja na vašo obremenitev. Zgradite sklad glav po meri, da vidite, kako obremenitev protokola porabi MTU. Podpira ugnezdene tunele (VXLAN znotraj VXLAN, GRE znotraj IPsec itd.).</p>
<div class="config-grid">
<div class="config-panel">
<h4>Konfiguracija okvirja</h4>
<div class="input-row">
<div class="input-group">
<label for="mtuInput">MTU (bajti):</label>
<input id="mtuInput" max="65535" min="576" step="1" type="number" value="1500"/>
</div>
<div class="input-group">
<label for="mtuPreset">Pogosti MTU:</label>
<select id="mtuPreset" onchange="applyMtuPreset()">
<option value="">Po meri</option>
<option selected="" value="1500">Ethernet (1500)</option>
<option value="1492">PPPoE (1492)</option>
<option value="1480">Predor GRE (1480)</option>
<option value="1450">VXLAN (1450)</option>
<option value="1400">IPsec (1400)</option>
<option value="9000">Jumbo okvir (9000)</option>
<option value="9216">Jumbo Max (9216)</option>
</select>
</div>
</div>
<div class="preset-section">
<h4>Hitre prednastavitve</h4>
<div class="preset-buttons">
<button class="preset-btn" onclick="applyPreset('standard')" type="button">Standardni TCP/IP</button>
<button class="preset-btn" onclick="applyPreset('vxlan')" type="button">Prekrivanje VXLAN</button>
<button class="preset-btn" onclick="applyPreset('ipsec')" type="button">IPsec VPN</button>
<button class="preset-btn" onclick="applyPreset('gre')" type="button">Predor GRE</button>
<button class="preset-btn" onclick="applyPreset('double-vxlan')" type="button">Dvojni VXLAN</button>
<button class="preset-btn" onclick="applyPreset('vxlan-gre')" type="button">VXLAN v GRE</button>
<button class="preset-btn" onclick="applyPreset('clear')" type="button">Počisti vse</button>
</div>
</div>
</div>
<div class="config-panel">
<h4>Graditelj sklada glave</h4>
<div class="stack-builder">
<div class="add-header-row">
<select id="headerSelect">
<optgroup label="Layer 2 - Data Link">
<option value="ethernet">Ethernet II (14 bajtov)</option>
<option value="vlan">Oznaka 802.1Q VLAN (4 bajti)</option>
<option value="qinq">Dvojni VLAN Q-in-Q (8 bajtov)</option>
<option value="pppoe">PPPoE (8 bajtov)</option>
</optgroup>
<optgroup label="Layer 2.5 - MPLS">
<option value="mpls">Oznaka MPLS (4 bajti)</option>
</optgroup>
<optgroup label="Layer 3 - Network">
<option value="ipv4">IPv4 (20 bajtov)</option>
<option value="ipv6">IPv6 (40 bajtov)</option>
</optgroup>
<optgroup label="Layer 4 - Transport">
<option value="tcp">TCP (20 bajtov)</option>
<option value="udp">UDP (8 bajtov)</option>
</optgroup>
<optgroup label="Tunnel Protocols">
<option value="vxlan">VXLAN (8 bajtov)</option>
<option value="geneve">GENEVE (8 bajtov)</option>
<option value="gre">GRE (4 bajti)</option>
<option value="gre-key">GRE s ključem (8 bajtov)</option>
<option value="nvgre">NVGRE (8 bajtov)</option>
<option value="ipsec">IPsec ESP (~50 bajtov)</option>
<option value="l2tp">L2TP (8 bajtov)</option>
<option value="gtp">GTP-U (8 bajtov)</option>
<option value="wireguard">WireGuard (32 bajtov)</option>
<option value="erspan">ERSPAN tipa II (8 bajtov)</option>
</optgroup>
</select>
<button class="add-btn" onclick="addHeader()" type="button">+ Dodaj</button>
</div>
<div class="tunnel-shortcuts">
<span style="color: rgba(255,255,255,0.7); font-size: 11px; margin-right: 5px;">Hitro dodajanje:</span>
<button class="tunnel-shortcut-btn" onclick="addTunnelGroup('vxlan')" type="button">+ Skupina VXLAN</button>
<button class="tunnel-shortcut-btn" onclick="addTunnelGroup('geneve')" type="button">+ Skupina GENEVE</button>
<button class="tunnel-shortcut-btn" onclick="addTunnelGroup('gre')" type="button">+ Skupina GRE</button>
<button class="tunnel-shortcut-btn" onclick="addTunnelGroup('ipsec')" type="button">+ Skupina IPsec</button>
<button class="tunnel-shortcut-btn" onclick="addTunnelGroup('inner-tcp')" type="button">+ Notranji TCP/IP</button>
</div>
<div class="header-stack" id="headerStack">
<div class="stack-empty">Kliknite »Dodaj« ali uporabite prednastavitve, da ustvarite svoj sklad glav</div>
</div>
<div class="stack-summary" id="stackSummary">
<span>Glave:<strong id="summaryCount">0</strong></span>
<span>Skupni režijski stroški:<strong id="summaryOverhead">0</strong>bajtov</span>
</div>
</div>
</div>
</div>
<button class="calc-button" onclick="visualizePacket()" type="button">Vizualizirajte strukturo paketa</button>
</div>
<div class="results-section" id="resultsSection" style="display: none;">
<div class="summary-cards" id="summaryCards">
<div class="summary-card" id="cardMtu">
<div class="card-label">Skupni MTU</div>
<div class="card-value"><span id="valueMtu">1500</span><span class="card-unit">B</span></div>
<div class="card-subtext">Velikost okvirja</div>
</div>
<div class="summary-card" id="cardOverhead">
<div class="card-label">Nadzemni del glave</div>
<div class="card-value"><span id="valueOverhead">54</span><span class="card-unit">B</span></div>
<div class="card-subtext" id="subtextOverhead">Vse glave skupaj</div>
</div>
<div class="summary-card" id="cardPayload">
<div class="card-label">Razpoložljiva nosilnost</div>
<div class="card-value"><span id="valuePayload">1446</span><span class="card-unit">B</span></div>
<div class="card-subtext">Za podatke aplikacije</div>
</div>
<div class="summary-card" id="cardEfficiency">
<div class="card-label">Učinkovitost</div>
<div class="card-value"><span id="valueEfficiency">96.4</span><span class="card-unit">%</span></div>
<div class="card-subtext">Nosilnost / MTU</div>
</div>
<div class="summary-card" id="cardMss">
<div class="card-label">Notranji TCP MSS</div>
<div class="card-value"><span id="valueMss">1406</span><span class="card-unit">B</span></div>
<div class="card-subtext">Priporočen MSS</div>
</div>
</div>
<div class="warnings-panel" id="warningsPanel" style="display: none;">
<h4>Konfiguracijska opozorila</h4>
<div id="warningsList"></div>
</div>
<div class="visualization-panel">
<div class="panel-header">
<span>Vizualizacija na ravni bajtov</span>
<span id="gridInfo">32 bajtov na vrstico</span>
</div>
<div class="panel-content">
<div class="byte-grid-container">
<svg id="byteGrid"></svg>
</div>
<div class="legend" id="legend"></div>
</div>
</div>
<div class="header-breakdown">
<div class="panel-header">
<span>Razčlenitev glave</span>
</div>
<table class="breakdown-table">
<thead>
<tr>
<th>#</th>
<th>Plast</th>
<th>Protokol</th>
<th>Velikost</th>
<th>Obseg bajtov</th>
<th>Opis</th>
</tr>
</thead>
<tbody id="breakdownBody">
</tbody>
</table>
</div>
<div class="mss-recommendation" id="mssRecommendation">
<h4>Priporočilo MSS</h4>
<p id="mssText"></p>
</div>
</div>
<div class="description-section">
<h3>O vizualizaciji glave paketa</h3>
<p>Razumevanje, kako glave protokola porabljajo vaš MTU, je ključnega pomena za optimizacijo delovanja omrežja. Vsaka plast enkapsulacije doda dodatne stroške, ki zmanjšajo razpoložljivi prostor za dejanske podatke aplikacije (tovor).</p>
<p><strong>Zakaj je to pomembno?</strong></p>
<ul>
<li><strong>Razdrobljenost:</strong>Če vaš paket preseže pot MTU, bo razdrobljen (IPv4) ali izpuščen (IPv6), kar bo povzročilo ponovne prenose in zakasnitev</li>
<li><strong>Prepustnost:</strong>Več režijskih stroškov pomeni manj koristne obremenitve na paket, kar zmanjša učinkovito prepustnost</li>
<li><strong>MSS Tuning:</strong>TCP-jeva največja velikost segmenta mora upoštevati vso enkapsulacijo, da se izognemo razdrobljenosti</li>
<li><strong>Ugnezdeni tuneli:</strong>Tehnologije, kot so VXLAN, GRE in IPsec, je mogoče združiti, kar znatno poveča stroške</li>
</ul>
<p><strong>Referenca velikosti glave:</strong></p>
<ul>
<li><strong>Ethernet II:</strong>14 bajtov (Dst MAC 6 + Src MAC 6 + EtherType 2)</li>
<li><strong>802.1Q VLAN:</strong>4 bajti na oznako</li>
<li><strong>MPLS:</strong>4 bajte na oznako</li>
<li><strong>IPv4:</strong>20 bajtov (najmanj, do 60 z možnostmi)</li>
<li><strong>IPv6:</strong>40 bajtov (fiksna osnovna glava)</li>
<li><strong>TCP:</strong>20 bajtov (najmanj, do 60 z možnostmi)</li>
<li><strong>UDP:</strong>8 bajtov</li>
<li><strong>VXLAN/GENEVE:</strong>8 bajtov (samo glava tunela)</li>
<li><strong>GRE:</strong>4 bajti osnovni, 8 bajti s ključem</li>
<li><strong>IPsec ESP:</strong>~50 bajtov tipično (odvisno od šifre)</li>
</ul>
</div>
</div>
<div class="tooltip" id="tooltip" style="display: none;"></div>
<script src="https://d3js.org/d3.v7.min.js"></script>
<script>
'use strict';

/**
 * Packet Header Visualizer
 * Supports arbitrary nesting of encapsulation protocols
 */

// Header definitions
const HEADERS = {
    'ethernet': {
        id: 'ethernet',
        name: 'Ethernet II',
        size: 14,
        layer: 2,
        layerName: 'L2',
        color: '#2196F3',
        description: 'Dst MAC (6B) + Src MAC (6B) + EtherType (2B)',
        rfc: 'RFC 894'
    },
    'vlan': {
        id: 'vlan',
        name: '802.1Q VLAN',
        size: 4,
        layer: 2,
        layerName: 'L2',
        color: '#03A9F4',
        description: 'TPID (2B) + TCI (2B)',
        rfc: 'IEEE 802.1Q'
    },
    'qinq': {
        id: 'qinq',
        name: 'Q-in-Q (802.1ad)',
        size: 8,
        layer: 2,
        layerName: 'L2',
        color: '#00BCD4',
        description: 'Outer VLAN (4B) + Inner VLAN (4B)',
        rfc: 'IEEE 802.1ad'
    },
    'mpls': {
        id: 'mpls',
        name: 'MPLS Label',
        size: 4,
        layer: 2.5,
        layerName: 'L2.5',
        color: '#009688',
        description: 'Label (20b) + TC (3b) + S (1b) + TTL (8b)',
        rfc: 'RFC 3031'
    },
    'pppoe': {
        id: 'pppoe',
        name: 'PPPoE',
        size: 8,
        layer: 2,
        layerName: 'L2',
        color: '#00ACC1',
        description: 'PPPoE header (6B) + PPP protocol (2B)',
        rfc: 'RFC 2516'
    },
    'ipv4': {
        id: 'ipv4',
        name: 'IPv4',
        size: 20,
        layer: 3,
        layerName: 'L3',
        color: '#4CAF50',
        description: 'Standard IPv4 header (no options)',
        rfc: 'RFC 791'
    },
    'ipv6': {
        id: 'ipv6',
        name: 'IPv6',
        size: 40,
        layer: 3,
        layerName: 'L3',
        color: '#8BC34A',
        description: 'Fixed-size IPv6 base header',
        rfc: 'RFC 8200'
    },
    'tcp': {
        id: 'tcp',
        name: 'TCP',
        size: 20,
        layer: 4,
        layerName: 'L4',
        color: '#FF9800',
        description: 'Standard TCP header (no options)',
        rfc: 'RFC 9293'
    },
    'udp': {
        id: 'udp',
        name: 'UDP',
        size: 8,
        layer: 4,
        layerName: 'L4',
        color: '#FFC107',
        description: 'Src Port + Dst Port + Length + Checksum',
        rfc: 'RFC 768'
    },
    'vxlan': {
        id: 'vxlan',
        name: 'VXLAN',
        size: 8,
        layer: 'tunnel',
        layerName: 'Tunnel',
        color: '#9C27B0',
        description: 'VXLAN header with 24-bit VNI',
        rfc: 'RFC 7348'
    },
    'geneve': {
        id: 'geneve',
        name: 'GENEVE',
        size: 8,
        layer: 'tunnel',
        layerName: 'Tunnel',
        color: '#AB47BC',
        description: 'Generic Network Virtualization Encapsulation',
        rfc: 'RFC 8926'
    },
    'gre': {
        id: 'gre',
        name: 'GRE',
        size: 4,
        layer: 'tunnel',
        layerName: 'Tunnel',
        color: '#7B1FA2',
        description: 'Basic GRE header',
        rfc: 'RFC 2784'
    },
    'gre-key': {
        id: 'gre-key',
        name: 'GRE with Key',
        size: 8,
        layer: 'tunnel',
        layerName: 'Tunnel',
        color: '#6A1B9A',
        description: 'GRE header with 32-bit key field',
        rfc: 'RFC 2890'
    },
    'nvgre': {
        id: 'nvgre',
        name: 'NVGRE',
        size: 8,
        layer: 'tunnel',
        layerName: 'Tunnel',
        color: '#8E24AA',
        description: 'Network Virtualization using GRE',
        rfc: 'RFC 7637'
    },
    'ipsec': {
        id: 'ipsec',
        name: 'IPsec ESP',
        size: 50,
        layer: 'tunnel',
        layerName: 'Tunnel',
        color: '#E91E63',
        description: 'ESP (8B) + IV (16B) + Pad (~10B) + ICV (16B)',
        rfc: 'RFC 4303',
        note: 'Size varies by cipher; ~50B for AES-GCM'
    },
    'l2tp': {
        id: 'l2tp',
        name: 'L2TP',
        size: 8,
        layer: 'tunnel',
        layerName: 'Tunnel',
        color: '#F06292',
        description: 'L2TP session header',
        rfc: 'RFC 2661'
    },
    'gtp': {
        id: 'gtp',
        name: 'GTP-U',
        size: 8,
        layer: 'tunnel',
        layerName: 'Tunnel',
        color: '#BA68C8',
        description: 'GPRS Tunneling Protocol User Plane',
        rfc: '3GPP TS 29.281'
    },
    'wireguard': {
        id: 'wireguard',
        name: 'WireGuard',
        size: 32,
        layer: 'tunnel',
        layerName: 'Tunnel',
        color: '#CE93D8',
        description: 'WireGuard transport + poly1305 tag (16B)',
        rfc: 'N/A'
    },
    'erspan': {
        id: 'erspan',
        name: 'ERSPAN Type II',
        size: 8,
        layer: 'tunnel',
        layerName: 'Tunnel',
        color: '#D81B60',
        description: 'Encapsulated Remote SPAN',
        rfc: 'N/A (Cisco)'
    }
};

// Preset configurations
const PRESETS = {
    'standard': {
        name: 'Standard TCP/IP',
        headers: ['ethernet', 'ipv4', 'tcp']
    },
    'vxlan': {
        name: 'VXLAN Overlay',
        headers: ['ethernet', 'ipv4', 'udp', 'vxlan', 'ethernet', 'ipv4', 'tcp']
    },
    'ipsec': {
        name: 'IPsec VPN',
        headers: ['ethernet', 'ipv4', 'ipsec', 'ipv4', 'tcp']
    },
    'gre': {
        name: 'GRE Tunnel',
        headers: ['ethernet', 'ipv4', 'gre', 'ipv4', 'tcp']
    },
    'double-vxlan': {
        name: 'Double VXLAN',
        headers: ['ethernet', 'ipv4', 'udp', 'vxlan', 'ethernet', 'ipv4', 'udp', 'vxlan', 'ethernet', 'ipv4', 'tcp']
    },
    'vxlan-gre': {
        name: 'VXLAN in GRE',
        headers: ['ethernet', 'ipv4', 'gre', 'ipv4', 'udp', 'vxlan', 'ethernet', 'ipv4', 'tcp']
    },
    'clear': {
        name: 'Clear All',
        headers: []
    }
};

// Tunnel groups for quick adding
const TUNNEL_GROUPS = {
    'vxlan': ['ipv4', 'udp', 'vxlan', 'ethernet'],
    'geneve': ['ipv4', 'udp', 'geneve', 'ethernet'],
    'gre': ['ipv4', 'gre'],
    'ipsec': ['ipv4', 'ipsec'],
    'inner-tcp': ['ipv4', 'tcp']
};

// Current header stack (array of header objects with unique IDs)
let headerStack = [];
let nextId = 1;

/**
 * Generate unique color variations for repeated headers
 */
function getColorVariation(baseColor, index) {
    // Slightly adjust hue/lightness for repeated headers
    const variation = (index % 5) * 15;
    // Simple approach: adjust opacity or return base
    return baseColor;
}

/**
 * Add a header to the stack
 */
function addHeader(headerId = null) {
    if (!headerId) {
        headerId = document.getElementById('headerSelect').value;
    }

    const headerDef = HEADERS[headerId];
    if (!headerDef) return;

    // Count how many of this type already exist
    const existingCount = headerStack.filter(h => h.id === headerId).length;

    headerStack.push({
        ...headerDef,
        uid: nextId++,
        instanceNum: existingCount + 1
    });

    renderHeaderStack();
    updateStackSummary();

    // Auto-update visualization if already shown
    if (document.getElementById('resultsSection').style.display !== 'none') {
        visualizePacket();
    }
}

/**
 * Add a tunnel group (e.g., IP+UDP+VXLAN+ETH)
 */
function addTunnelGroup(groupName) {
    const group = TUNNEL_GROUPS[groupName];
    if (!group) return;

    group.forEach(headerId => {
        addHeader(headerId);
    });
}

/**
 * Remove a header from the stack
 */
function removeHeader(uid) {
    headerStack = headerStack.filter(h => h.uid !== uid);
    renderHeaderStack();
    updateStackSummary();

    if (document.getElementById('resultsSection').style.display !== 'none') {
        visualizePacket();
    }
}

/**
 * Move a header up in the stack
 */
function moveHeaderUp(uid) {
    const index = headerStack.findIndex(h => h.uid === uid);
    if (index > 0) {
        [headerStack[index - 1], headerStack[index]] = [headerStack[index], headerStack[index - 1]];
        renderHeaderStack();
        if (document.getElementById('resultsSection').style.display !== 'none') {
            visualizePacket();
        }
    }
}

/**
 * Move a header down in the stack
 */
function moveHeaderDown(uid) {
    const index = headerStack.findIndex(h => h.uid === uid);
    if (index < headerStack.length - 1) {
        [headerStack[index], headerStack[index + 1]] = [headerStack[index + 1], headerStack[index]];
        renderHeaderStack();
        if (document.getElementById('resultsSection').style.display !== 'none') {
            visualizePacket();
        }
    }
}

/**
 * Render the header stack UI
 */
function renderHeaderStack() {
    const container = document.getElementById('headerStack');

    if (headerStack.length === 0) {
        container.innerHTML = '<div class="stack-empty">Click "+ Add" or use presets to build your header stack</div>';
        return;
    }

    let html = '';
    headerStack.forEach((header, index) => {
        const instanceLabel = header.instanceNum > 1 ? ` #${header.instanceNum}` : '';
        html += `
            <div class="stack-item" data-uid="${header.uid}">
                <span class="item-number">${index + 1}</span>
                <span class="item-color" style="background: ${header.color}"></span>
                <span class="item-name">${header.name}${instanceLabel}</span>
                <span class="item-layer">${header.layerName}</span>
                <span class="item-size">${header.size}B</span>
                <button type="button" class="item-delete" onclick="removeHeader(${header.uid})" title="Remove">×</button>
            </div>
        `;
    });

    container.innerHTML = html;
}

/**
 * Update the stack summary
 */
function updateStackSummary() {
    const totalOverhead = headerStack.reduce((sum, h) => sum + h.size, 0);
    document.getElementById('summaryCount').textContent = headerStack.length;
    document.getElementById('summaryOverhead').textContent = totalOverhead;
}

/**
 * Apply a preset configuration
 */
function applyPreset(presetName) {
    const preset = PRESETS[presetName];
    if (!preset) return;

    // Clear current stack
    headerStack = [];
    nextId = 1;

    // Add preset headers
    preset.headers.forEach(headerId => {
        const headerDef = HEADERS[headerId];
        if (headerDef) {
            const existingCount = headerStack.filter(h => h.id === headerId).length;
            headerStack.push({
                ...headerDef,
                uid: nextId++,
                instanceNum: existingCount + 1
            });
        }
    });

    renderHeaderStack();
    updateStackSummary();

    // Update preset button styles
    document.querySelectorAll('.preset-btn').forEach(btn => btn.classList.remove('active'));
    if (event && event.target) {
        event.target.classList.add('active');
    }

    // Auto-visualize
    visualizePacket();
}

/**
 * Apply MTU preset
 */
function applyMtuPreset() {
    const preset = document.getElementById('mtuPreset').value;
    if (preset) {
        document.getElementById('mtuInput').value = preset;
        if (document.getElementById('resultsSection').style.display !== 'none') {
            visualizePacket();
        }
    }
}

/**
 * Build the positioned header stack for visualization
 */
function buildPositionedStack() {
    const positioned = [];
    let currentByte = 0;

    headerStack.forEach((header, index) => {
        positioned.push({
            ...header,
            index: index,
            startByte: currentByte,
            endByte: currentByte + header.size - 1
        });
        currentByte += header.size;
    });

    return positioned;
}

/**
 * Validate the header stack and return warnings
 */
function validateStack(stack) {
    const warnings = [];

    if (stack.length === 0) {
        return warnings;
    }

    // Check for common issues
    let lastLayer = 0;
    let hasOuterTransport = false;
    let tunnelDepth = 0;

    for (let i = 0; i < stack.length; i++) {
        const header = stack[i];
        const prevHeader = i > 0 ? stack[i - 1] : null;

        // Track tunnel depth
        if (header.layer === 'tunnel') {
            tunnelDepth++;
        }

        // Check if L4 tunnel protocol has required transport
        const udpTunnels = ['vxlan', 'geneve', 'l2tp', 'gtp', 'wireguard'];
        if (udpTunnels.includes(header.id)) {
            // Look backwards for UDP
            let foundUdp = false;
            for (let j = i - 1; j >= 0; j--) {
                if (stack[j].id === 'udp') {
                    foundUdp = true;
                    break;
                }
                if (stack[j].layer === 'tunnel') break; // Stop at previous tunnel
            }
            if (!foundUdp) {
                warnings.push(`${header.name} typically requires UDP encapsulation`);
            }
        }

        // Check if tunnel has IP before it
        if (header.layer === 'tunnel') {
            let foundIp = false;
            for (let j = i - 1; j >= 0; j--) {
                if (stack[j].id === 'ipv4' || stack[j].id === 'ipv6') {
                    foundIp = true;
                    break;
                }
                if (stack[j].layer === 'tunnel') break;
            }
            if (!foundIp) {
                warnings.push(`${header.name} typically requires an IP header`);
            }
        }
    }

    // Deep nesting warning
    if (tunnelDepth > 3) {
        warnings.push(`Deep nesting detected (${tunnelDepth} tunnel layers). This may cause significant overhead.`);
    }

    return warnings;
}

/**
 * Calculate packet metrics
 */
function calculateMetrics(positionedStack, mtu) {
    const totalOverhead = positionedStack.reduce((sum, h) => sum + h.size, 0);
    const payload = Math.max(0, mtu - totalOverhead);
    const efficiency = mtu > 0 ? (payload / mtu) * 100 : 0;

    // MSS is payload available after all headers
    const mss = payload;

    return {
        mtu,
        overhead: totalOverhead,
        payload,
        efficiency: efficiency.toFixed(1),
        mss
    };
}

/**
 * Render the byte grid visualization with D3
 */
function renderByteGrid(positionedStack, mtu) {
    const svg = d3.select('#byteGrid');
    svg.selectAll('*').remove();

    const cellSize = 16;
    const cellPadding = 2;
    const bytesPerRow = 32;
    const totalCells = Math.min(mtu, 2048); // Cap visualization at 2048 bytes
    const rows = Math.ceil(totalCells / bytesPerRow);

    const width = bytesPerRow * (cellSize + cellPadding) + 60;
    const height = rows * (cellSize + cellPadding) + 40;

    svg.attr('width', width).attr('height', height);

    // Create header lookup map
    const byteToHeader = new Map();
    positionedStack.forEach(header => {
        for (let i = header.startByte; i <= header.endByte && i < totalCells; i++) {
            byteToHeader.set(i, header);
        }
    });

    const totalOverhead = positionedStack.reduce((sum, h) => sum + h.size, 0);

    // Add row labels
    for (let row = 0; row < rows; row++) {
        svg.append('text')
            .attr('x', 5)
            .attr('y', 30 + row * (cellSize + cellPadding) + cellSize / 2 + 4)
            .attr('font-size', '10px')
            .attr('fill', '#666')
            .attr('font-family', 'Courier New, monospace')
            .text(row * bytesPerRow);
    }

    // Create cells
    const tooltip = d3.select('#tooltip');

    for (let i = 0; i < totalCells; i++) {
        const row = Math.floor(i / bytesPerRow);
        const col = i % bytesPerRow;
        const x = 50 + col * (cellSize + cellPadding);
        const y = 20 + row * (cellSize + cellPadding);

        let color, header;
        if (byteToHeader.has(i)) {
            header = byteToHeader.get(i);
            color = header.color;
        } else if (i < mtu) {
            color = '#607D8B';
            header = { name: 'Payload', description: 'Application data', layerName: 'Data' };
        } else {
            color = '#eee';
            header = null;
        }

        const rect = svg.append('rect')
            .attr('x', x)
            .attr('y', y)
            .attr('width', cellSize)
            .attr('height', cellSize)
            .attr('fill', color)
            .attr('rx', 2)
            .attr('stroke', '#fff')
            .attr('stroke-width', 1)
            .style('cursor', header ? 'pointer' : 'default');

        if (header) {
            rect.on('mouseover', function(event) {
                d3.select(this).attr('stroke', '#333').attr('stroke-width', 2);

                const instanceLabel = header.instanceNum > 1 ? ` #${header.instanceNum}` : '';
                let tooltipContent = `<div class="tooltip-header">${header.name}${instanceLabel}</div>`;
                if (header.startByte !== undefined) {
                    tooltipContent += `<div class="tooltip-detail">Bytes ${header.startByte}-${header.endByte} (${header.size}B)</div>`;
                } else {
                    tooltipContent += `<div class="tooltip-detail">Byte ${i}</div>`;
                }
                tooltipContent += `<div style="margin-top: 5px; font-size: 11px;">${header.description || ''}</div>`;
                if (header.rfc) {
                    tooltipContent += `<div style="margin-top: 3px; font-size: 10px; color: #888;">${header.rfc}</div>`;
                }

                tooltip.html(tooltipContent)
                    .style('display', 'block')
                    .style('left', (event.pageX + 10) + 'px')
                    .style('top', (event.pageY - 10) + 'px');
            })
            .on('mouseout', function() {
                d3.select(this).attr('stroke', '#fff').attr('stroke-width', 1);
                tooltip.style('display', 'none');
            })
            .on('mousemove', function(event) {
                tooltip.style('left', (event.pageX + 10) + 'px')
                    .style('top', (event.pageY - 10) + 'px');
            });
        }
    }

    // Update grid info
    const truncated = mtu > 2048 ? ' (truncated)' : '';
    document.getElementById('gridInfo').textContent = `${bytesPerRow} bytes/row | ${totalCells} bytes shown${truncated}`;
}

/**
 * Render the legend
 */
function renderLegend(positionedStack) {
    const legend = document.getElementById('legend');
    const seen = new Map();

    positionedStack.forEach(header => {
        const key = header.id;
        if (!seen.has(key)) {
            seen.set(key, { name: header.name, color: header.color, count: 1 });
        } else {
            seen.get(key).count++;
        }
    });

    let html = '';
    seen.forEach((info, key) => {
        const countLabel = info.count > 1 ? ` (×${info.count})` : '';
        html += `<div class="legend-item">
            <div class="legend-color" style="background: ${info.color}"></div>
            <span>${info.name}${countLabel}</span>
        </div>`;
    });

    // Add payload
    html += `<div class="legend-item">
        <div class="legend-color" style="background: #607D8B"></div>
        <span>Payload</span>
    </div>`;

    legend.innerHTML = html;
}

/**
 * Render the breakdown table
 */
function renderBreakdownTable(positionedStack, payloadSize, mtu) {
    const tbody = document.getElementById('breakdownBody');
    let html = '';

    positionedStack.forEach((header, index) => {
        const layerClass = `layer-${header.layerName.toLowerCase().replace('.', '')}`;
        const instanceLabel = header.instanceNum > 1 ? ` #${header.instanceNum}` : '';
        html += `<tr>
            <td>${index + 1}</td>
            <td><span class="layer-badge ${layerClass}">${header.layerName}</span></td>
            <td><strong>${header.name}${instanceLabel}</strong></td>
            <td>${header.size} bytes</td>
            <td class="byte-range">${header.startByte} - ${header.endByte}</td>
            <td>${header.description || '-'}</td>
        </tr>`;
    });

    // Add payload row
    const payloadStart = positionedStack.length > 0 ? positionedStack[positionedStack.length - 1].endByte + 1 : 0;
    const payloadEnd = Math.min(payloadStart + payloadSize - 1, mtu - 1);
    html += `<tr>
        <td>-</td>
        <td><span class="layer-badge layer-payload">Data</span></td>
        <td><strong>Payload</strong></td>
        <td>${payloadSize} bytes</td>
        <td class="byte-range">${payloadSize > 0 ? `${payloadStart} - ${payloadEnd}` : 'N/A'}</td>
        <td>Available for application data</td>
    </tr>`;

    tbody.innerHTML = html;
}

/**
 * Update summary cards
 */
function updateSummaryCards(metrics) {
    document.getElementById('valueMtu').textContent = metrics.mtu;
    document.getElementById('valueOverhead').textContent = metrics.overhead;
    document.getElementById('valuePayload').textContent = metrics.payload;
    document.getElementById('valueEfficiency').textContent = metrics.efficiency;
    document.getElementById('valueMss').textContent = metrics.mss;

    // Update card styling based on values
    const efficiencyCard = document.getElementById('cardEfficiency');
    const payloadCard = document.getElementById('cardPayload');

    efficiencyCard.className = 'summary-card';
    payloadCard.className = 'summary-card';

    if (parseFloat(metrics.efficiency) < 50) {
        efficiencyCard.classList.add('danger');
    } else if (parseFloat(metrics.efficiency) < 70) {
        efficiencyCard.classList.add('warning');
    }

    if (metrics.payload < 100) {
        payloadCard.classList.add('danger');
    } else if (metrics.payload < 500) {
        payloadCard.classList.add('warning');
    }
}

/**
 * Show warnings
 */
function showWarnings(warnings) {
    const panel = document.getElementById('warningsPanel');
    const list = document.getElementById('warningsList');

    if (warnings.length === 0) {
        panel.style.display = 'none';
        return;
    }

    list.innerHTML = warnings.map(w => `<div class="warning-item">${w}</div>`).join('');
    panel.style.display = 'block';
}

/**
 * Generate MSS recommendation text
 */
function generateMssRecommendation(positionedStack, metrics, mtu) {
    const mssText = document.getElementById('mssText');
    const tunnelCount = positionedStack.filter(h => h.layer === 'tunnel').length;

    let text = '';

    if (metrics.payload <= 0) {
        text = `<strong style="color: #c62828;">Warning:</strong> Your encapsulation overhead (${metrics.overhead} bytes) exceeds the MTU (${mtu} bytes). No payload space is available. Increase MTU or reduce encapsulation.`;
    } else if (tunnelCount > 0) {
        text = `For traffic through this ${tunnelCount}-layer tunnel configuration, configure inner TCP MSS to <code>${metrics.mss}</code> bytes to prevent fragmentation. `;
        text += `Total tunnel overhead: ${metrics.overhead} bytes.`;

        const hasIpv6 = positionedStack.some(h => h.id === 'ipv6');
        if (hasIpv6) {
            text += `<br><br><strong>Note:</strong> IPv6 does not fragment in transit. Ensure PMTUD works or configure MSS clamping.`;
        }

        text += `<br><br><strong>Cisco IOS:</strong> <code>ip tcp adjust-mss ${metrics.mss}</code>`;
        text += `<br><strong>Linux iptables:</strong> <code>iptables -t mangle -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --set-mss ${metrics.mss}</code>`;
    } else if (positionedStack.length > 0) {
        text = `Standard configuration with ${metrics.overhead} bytes overhead. `;
        text += `Maximum TCP segment payload: <code>${metrics.mss}</code> bytes (${metrics.efficiency}% efficiency).`;
    } else {
        text = `Add headers to your stack to see MSS recommendations.`;
    }

    mssText.innerHTML = text;
}

/**
 * Main visualization function
 */
function visualizePacket() {
    const mtu = parseInt(document.getElementById('mtuInput').value) || 1500;

    // Validate MTU
    if (mtu < 576) {
        alert('MTU must be at least 576 bytes (IPv4 minimum)');
        return;
    }
    if (mtu > 65535) {
        alert('MTU cannot exceed 65535 bytes');
        return;
    }

    // Build positioned stack
    const positionedStack = buildPositionedStack();

    // Validate and get warnings
    const warnings = validateStack(positionedStack);

    // Calculate metrics
    const metrics = calculateMetrics(positionedStack, mtu);

    // Update UI
    updateSummaryCards(metrics);
    showWarnings(warnings);
    renderByteGrid(positionedStack, mtu);
    renderLegend(positionedStack);
    renderBreakdownTable(positionedStack, metrics.payload, mtu);
    generateMssRecommendation(positionedStack, metrics, mtu);

    // Show results
    document.getElementById('resultsSection').style.display = 'block';

    // Scroll to results
    document.getElementById('resultsSection').scrollIntoView({ behavior: 'smooth', block: 'start' });
}

/**
 * Initialize on page load
 */
document.addEventListener('DOMContentLoaded', function() {
    // Add enter key support for MTU input
    document.getElementById('mtuInput').addEventListener('keypress', function(e) {
        if (e.key === 'Enter') {
            visualizePacket();
        }
    });

    // MTU input change handler
    document.getElementById('mtuInput').addEventListener('change', function() {
        document.getElementById('mtuPreset').value = '';
        if (document.getElementById('resultsSection').style.display !== 'none') {
            visualizePacket();
        }
    });

    // Initialize with standard TCP/IP preset
    applyPreset('standard');

    console.log('Packet Header Visualizer initialized');
});
</script>