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id="vector-appearance-pinned-container" class="vector-pinned-container"> <div id="vector-appearance" class="vector-appearance vector-pinnable-element"> <div class="vector-pinnable-header vector-appearance-pinnable-header vector-pinnable-header-pinned" data-feature-name="appearance-pinned" data-pinnable-element-id="vector-appearance" data-pinned-container-id="vector-appearance-pinned-container" data-unpinned-container-id="vector-appearance-unpinned-container" > <div class="vector-pinnable-header-label">Aspetto</div> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-appearance.pin">sposta nella barra laterale</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-appearance.unpin">nascondi</button> </div> </div> </div> </nav> </div> </div> <div id="bodyContent" class="vector-body" aria-labelledby="firstHeading" data-mw-ve-target-container> <div class="vector-body-before-content"> <div class="mw-indicators"> </div> <div id="siteSub" class="noprint">Da Wikipedia, l'enciclopedia libera.</div> </div> <div id="contentSub"><div id="mw-content-subtitle"></div></div> <div id="mw-content-text" class="mw-body-content"><div class="mw-content-ltr mw-parser-output" lang="it" dir="ltr"><p>L’<i><b>Explicit Congestion Notification</b></i> (in italiano "notifica esplicita di congestione"), abbreviato <b>ECN</b>, è un'estensione dei <a href="/wiki/Suite_di_protocolli_Internet" title="Suite di protocolli Internet">protocolli TCP/IP</a> definita nella <a class="external mw-magiclink-rfc" rel="nofollow" href="https://tools.ietf.org/html/rfc3168">RFC 3168</a> che consente di rilevare la presenza di <a href="/wiki/Congestione_(reti)" title="Congestione (reti)">congestione di rete</a> senza perdita di <a href="/wiki/Pacchetto_(reti)" title="Pacchetto (reti)">pacchetti</a>. Questa funzionalità è disponibile solo quando entrambi i terminali e l'infrastruttura di rete che li connette la supportano.<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> </p><p>In assenza di ECN, le reti basate su TCP/IP segnalano la presenza di congestione mediante l'eliminazione di alcuni pacchetti, utilizzando un meccanismo chiamato <i><a href="/wiki/Random_early_detection" title="Random early detection">random early detection</a></i>. Quando è attiva l'ECN invece un <a href="/wiki/Router" title="Router">router</a> può inserire un marcatore nell’<i><a href="/wiki/Header" title="Header">header</a></i> di un pacchetto IP per segnalare un'imminente congestione. Il destinatario rimanda quindi il marcatore al mittente del pacchetto, il quale riduce così la sua velocità di trasmissione.<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Funzionamento">Funzionamento</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Explicit_Congestion_Notification&veaction=edit&section=1" title="Modifica la sezione Funzionamento" class="mw-editsection-visualeditor"><span>modifica</span></a><span class="mw-editsection-divider"> | </span><a href="/w/index.php?title=Explicit_Congestion_Notification&action=edit&section=1" title="Edit section's source code: Funzionamento"><span>modifica wikitesto</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>L'imminente congestione è indicata impostando il campo ECN di un pacchetto IP packet a CE (<i>Congestion Experienced</i>) ed è rimandata indietro dal destinatario al mittente impostando dei bit specifici nell’<i>header</i>. </p> <div class="mw-heading mw-heading3"><h3 id="ECN_su_IP">ECN su IP</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Explicit_Congestion_Notification&veaction=edit&section=2" title="Modifica la sezione ECN su IP" class="mw-editsection-visualeditor"><span>modifica</span></a><span class="mw-editsection-divider"> | </span><a href="/w/index.php?title=Explicit_Congestion_Notification&action=edit&section=2" title="Edit section's source code: ECN su IP"><span>modifica wikitesto</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>L'ECN utilizza i due <a href="/wiki/Ordine_dei_bit" title="Ordine dei bit">bit meno significativi</a> (cioè quelli più a destra) del campo <i>Traffic Class</i> degli <i>header</i> <a href="/wiki/IPv4" title="IPv4">IPv4</a> e <a href="/wiki/IPv6" title="IPv6">IPv6</a> per trasmettere quattro possibili stati: </p> <ul><li><code>00</code> – ECN non supportato</li> <li><code>01</code> – ECN supportato</li> <li><code>10</code> – ECN supportato</li> <li><code>11</code> – <i>Congestion Experienced</i> (CE)</li></ul> <p>Quando entrambi i terminali supportano l'ECN, i pacchetti vengono marcati con i codici <code>01</code> o <code>10</code>, che sono equivalenti. In presenza di congestione, se il router che la rileva supporta l'ECN cambierà il codice in <code>11</code> (CE) invece di eliminare dei pacchetti. Il nuovo codice sarà ricevuto dal destinatario, che lo rimanderà al mittente dei pacchetti, il quale ridurrà la sua velocità di trasmissione.<sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="ECN_su_TCP">ECN su TCP</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Explicit_Congestion_Notification&veaction=edit&section=3" title="Modifica la sezione ECN su TCP" class="mw-editsection-visualeditor"><span>modifica</span></a><span class="mw-editsection-divider"> | </span><a href="/w/index.php?title=Explicit_Congestion_Notification&action=edit&section=3" title="Edit section's source code: ECN su TCP"><span>modifica wikitesto</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Il TCP supporta ECN usando due diversi indicatori nell’<i>header</i> TCP. Il primo, chiamato <i>ECN-Echo</i> (ECE), è usato per rimandare l'avviso di congestione al mittente per chiedere di ridurre la velocità di trasmissione. Il secondo, denominato <i>Congestion Window Reduced</i> (CWR), è impostato dal mittente per segnalare che la notifica di congestione è stata ricevuta. </p><p>L'uso dell'ECN in una connessione TCP è facoltativo ed è possibile solo se è stabilito al momento della creazione della connessione aggiungendo apposite opzioni nei pacchetti di sincronizzazione iniziali SYN e SYN-ACK. Questo processo è chiamato negoziazione e serve a stabilire se tutti i dispositivi su cui è creata la connessione supportano l'ECN. Una volta che l'utilizzo dell'ECN è stato negoziato correttamente tra le parti, quando il destinatario riceve un pacchetto in cui è presente il marcatore CE, reinvia quest'informazione al mittente utilizzando l'indicatore ECE nell’<i>header</i> TCP. Il mittente quindi ridurrà la sua velocità di trasmissione dei pacchetti e invierà una conferma mediante l'indicatore CWR.<sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="ECN_su_altri_protocolli">ECN su altri protocolli</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Explicit_Congestion_Notification&veaction=edit&section=4" title="Modifica la sezione ECN su altri protocolli" class="mw-editsection-visualeditor"><span>modifica</span></a><span class="mw-editsection-divider"> | </span><a href="/w/index.php?title=Explicit_Congestion_Notification&action=edit&section=4" title="Edit section's source code: ECN su altri protocolli"><span>modifica wikitesto</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>L'ECN è definita anche su altri protobolli di comunicazione a livello di trasporto, tra cui <a href="/wiki/Datagram_Congestion_Control_Protocol" title="Datagram Congestion Control Protocol">DCCP</a><sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> e <a href="/wiki/Stream_Control_Transmission_Protocol" title="Stream Control Transmission Protocol">SCTP</a>.<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> </p><p>È anche possibile usare l'ECN nei protocolli basati su <a href="/wiki/User_Datagram_Protocol" title="User Datagram Protocol">UDP</a>, tuttavia è supportato solo quelli più recenti, come ad esempio <a href="/wiki/QUIC" title="QUIC">QUIC</a>.<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Supporto">Supporto</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Explicit_Congestion_Notification&veaction=edit&section=5" title="Modifica la sezione Supporto" class="mw-editsection-visualeditor"><span>modifica</span></a><span class="mw-editsection-divider"> | </span><a href="/w/index.php?title=Explicit_Congestion_Notification&action=edit&section=5" title="Edit section's source code: Supporto"><span>modifica wikitesto</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><a href="/wiki/Microsoft_Windows" title="Microsoft Windows">Microsoft Windows</a> supporta l'ECN a partire dalle versioni <a href="/wiki/Windows_Vista" title="Windows Vista">Vista</a> e <a href="/wiki/Windows_Server_2012" title="Windows Server 2012">Server 2012</a>.<sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> Nelle versioni Server è abilitato di default, mentre in quelle non Server deve essere abilitato manualmente.<sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> </p><p>Linux supporta l'ECN a partire dalla versione 2.4.20 del <a href="/wiki/Linux_(kernel)" title="Linux (kernel)">kernel Linux</a> rilasciata nel novembre 2002.<sup id="cite_ref-10" class="reference"><a href="#cite_note-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> </p><p>L'ECN è stato introdotto in <a href="/wiki/Mac_OS_X_Leopard" title="Mac OS X Leopard">Mac OS X 10.5</a> ed è abilitato di default da <a href="/wiki/OS_X_El_Capitan" title="OS X El Capitan">OS X 10.11</a>.<sup id="cite_ref-11" class="reference"><a href="#cite_note-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> È anche supportato e abilitato di default da <a href="/wiki/IOS_9" title="IOS 9">iOS 9</a>.<sup id="cite_ref-12" class="reference"><a href="#cite_note-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Note">Note</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Explicit_Congestion_Notification&veaction=edit&section=6" title="Modifica la sezione Note" class="mw-editsection-visualeditor"><span>modifica</span></a><span class="mw-editsection-divider"> | </span><a href="/w/index.php?title=Explicit_Congestion_Notification&action=edit&section=6" title="Edit section's source code: Note"><span>modifica wikitesto</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="mw-references-wrap mw-references-columns"><ol class="references"> <li id="cite_note-1"><a href="#cite_ref-1"><b>^</b></a> <span class="reference-text"><cite class="citation web" style="font-style:normal">(<span style="font-weight:bolder; font-size:80%"><abbr title="inglese">EN</abbr></span>) <a rel="nofollow" class="external text" href="https://docs.nvidia.com/networking/display/mlnxenv23100541/explicit+congestion+notification+(ecn)"><span style="font-style:italic;">Explicit Congestion Notification (ECN)</span></a>, su <span style="font-style:italic;">docs.nvidia.com</span>.</cite></span> </li> <li id="cite_note-2"><a href="#cite_ref-2"><b>^</b></a> <span class="reference-text"><cite class="citation web" style="font-style:normal">(<span style="font-weight:bolder; font-size:80%"><abbr title="inglese">EN</abbr></span>) <a rel="nofollow" class="external text" href="https://www.juniper.net/documentation/us/en/software/junos/cos/topics/concept/cos-qfx-series-explicit-congestion-notification-understanding.html"><span style="font-style:italic;">Understanding CoS Explicit Congestion Notification</span></a>, su <span style="font-style:italic;">juniper.net</span>.</cite></span> </li> <li id="cite_note-3"><a href="#cite_ref-3"><b>^</b></a> <span class="reference-text"><cite class="citation web" style="font-style:normal">(<span style="font-weight:bolder; font-size:80%"><abbr title="inglese">EN</abbr></span>) <a rel="nofollow" class="external text" href="https://www.arubanetworks.com/techdocs/AOS-CX/10.11/HTML/qos_8400/Content/Chp_DCB/dcb-ip-ecn.htm"><span style="font-style:italic;">IP explicit congestion notification</span></a>, su <span style="font-style:italic;">arubanetworks.com</span>.</cite></span> </li> <li id="cite_note-4"><a href="#cite_ref-4"><b>^</b></a> <span class="reference-text"><cite class="citation web" style="font-style:normal">(<span style="font-weight:bolder; font-size:80%"><abbr title="inglese">EN</abbr></span>) <a rel="nofollow" class="external text" href="https://www.geeksforgeeks.org/what-is-ecnexplicit-congestion-notification/"><span style="font-style:italic;">What is ECN (Explicit Congestion Notification)?</span></a>, su <span style="font-style:italic;">geeksforgeeks.org</span>.</cite></span> </li> <li id="cite_note-5"><a href="#cite_ref-5"><b>^</b></a> <span class="reference-text"><cite class="citation web" style="font-style:normal">(<span style="font-weight:bolder; font-size:80%"><abbr title="inglese">EN</abbr></span>) <a rel="nofollow" class="external text" href="https://datatracker.ietf.org/doc/html/rfc4340#page-96"><span style="font-style:italic;">Datagram Congestion Control Protocol (DCCP)</span></a>, su <span style="font-style:italic;">datatracker.ietf.org</span>.</cite></span> </li> <li id="cite_note-6"><a href="#cite_ref-6"><b>^</b></a> <span class="reference-text"><cite class="citation web" style="font-style:normal">(<span style="font-weight:bolder; font-size:80%"><abbr title="inglese">EN</abbr></span>) <a rel="nofollow" class="external text" href="https://www.ietf.org/archive/id/draft-stewart-tsvwg-sctpecn-06.html"><span style="font-style:italic;">Explicit Congestion Notification for the Stream Control Transmission Protocol</span></a>, su <span style="font-style:italic;">ietf.org</span>.</cite></span> </li> <li id="cite_note-7"><a href="#cite_ref-7"><b>^</b></a> <span class="reference-text"><cite class="citation web" style="font-style:normal">(<span style="font-weight:bolder; font-size:80%"><abbr title="inglese">EN</abbr></span>) <a rel="nofollow" class="external text" href="https://github.com/quicwg/base-drafts/wiki/ECN-in-QUIC"><span style="font-style:italic;">ECN in QUIC</span></a>, su <span style="font-style:italic;">github.com</span>.</cite></span> </li> <li id="cite_note-8"><a href="#cite_ref-8"><b>^</b></a> <span class="reference-text"><cite class="citation web" style="font-style:normal">(<span style="font-weight:bolder; font-size:80%"><abbr title="inglese">EN</abbr></span>) <a rel="nofollow" class="external text" href="https://learn.microsoft.com/en-us/previous-versions/windows/it-pro/windows-vista/bb726965(v=technet.10)"><span style="font-style:italic;">New Networking Features in Windows Server 2008 and Windows Vista</span></a>, su <span style="font-style:italic;">learn.microsoft.com</span>.</cite></span> </li> <li id="cite_note-9"><a href="#cite_ref-9"><b>^</b></a> <span class="reference-text"><cite class="citation web" style="font-style:normal">(<span style="font-weight:bolder; font-size:80%"><abbr title="inglese">EN</abbr></span>) <a rel="nofollow" class="external text" href="https://answers.microsoft.com/en-us/windows/forum/all/how-to-enable-explicit-congestion-notification-ecn/84baca68-49c0-47f1-93c0-7bed1bb07098"><span style="font-style:italic;">How to enable Explicit Congestion Notification (ECN) in Windows 7?</span></a>, su <span style="font-style:italic;">answers.microsoft.com</span>.</cite></span> </li> <li id="cite_note-10"><a href="#cite_ref-10"><b>^</b></a> <span class="reference-text"><cite class="citation web" style="font-style:normal">(<span style="font-weight:bolder; font-size:80%"><abbr title="inglese">EN</abbr></span>) <a rel="nofollow" class="external text" href="https://datatag.web.cern.ch/datatag/papers/tr-datatag-2004-1.pdf"><span style="font-style:italic;">A Map of the Networking Code in Linux Kernel 2.4.20</span></a> (<span style="font-weight: bolder; font-size:80%"><abbr title="documento in formato PDF">PDF</abbr></span>), su <span style="font-style:italic;">datatag.web.cern.ch</span>.</cite></span> </li> <li id="cite_note-11"><a href="#cite_ref-11"><b>^</b></a> <span class="reference-text"><cite class="citation web" style="font-style:normal">(<span style="font-weight:bolder; font-size:80%"><abbr title="inglese">EN</abbr></span>) <a rel="nofollow" class="external text" href="https://www.icir.org/floyd/ecn.html#implementations"><span style="font-style:italic;">Implementation and Deployment of ECN</span></a>, su <span style="font-style:italic;">icir.org</span>.</cite></span> </li> <li id="cite_note-12"><a href="#cite_ref-12"><b>^</b></a> <span class="reference-text"><cite class="citation web" style="font-style:normal">(<span style="font-weight:bolder; font-size:80%"><abbr title="inglese">EN</abbr></span>) <a rel="nofollow" class="external text" href="https://developer.apple.com/forums/thread/4971"><span style="font-style:italic;">Notes from Your App and Next Generation Networks session</span></a>, su <span style="font-style:italic;">developer.apple.com</span>.</cite></span> </li> </ol></div> <div class="mw-heading mw-heading2"><h2 id="Voci_correlate">Voci correlate</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Explicit_Congestion_Notification&veaction=edit&section=7" title="Modifica la sezione Voci correlate" class="mw-editsection-visualeditor"><span>modifica</span></a><span class="mw-editsection-divider"> | </span><a href="/w/index.php?title=Explicit_Congestion_Notification&action=edit&section=7" title="Edit section's source code: Voci correlate"><span>modifica wikitesto</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/Controllo_della_congestione" title="Controllo della congestione">Controllo della congestione</a></li> <li><a href="/wiki/Controllo_della_congestione_in_TCP" title="Controllo della congestione in TCP">Controllo della congestione in TCP</a></li></ul> <div class="mw-heading mw-heading2"><h2 id="Collegamenti_esterni">Collegamenti esterni</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Explicit_Congestion_Notification&veaction=edit&section=8" title="Modifica la sezione Collegamenti esterni" class="mw-editsection-visualeditor"><span>modifica</span></a><span class="mw-editsection-divider"> | </span><a href="/w/index.php?title=Explicit_Congestion_Notification&action=edit&section=8" title="Edit section's source code: Collegamenti esterni"><span>modifica wikitesto</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><cite class="citation web" style="font-style:normal">(<span style="font-weight:bolder; font-size:80%"><abbr title="inglese">EN</abbr></span>) <a rel="nofollow" class="external text" href="https://datatracker.ietf.org/doc/html/rfc3168"><span style="font-style:italic;">RFC 3168</span></a>, su <span style="font-style:italic;">datatracker.ietf.org</span>.</cite></li> <li><cite class="citation web" style="font-style:normal">(<span style="font-weight:bolder; font-size:80%"><abbr title="tedesco">DE</abbr></span>) <a rel="nofollow" class="external text" href="https://www.msxfaq.de/netzwerk/grundlagen/ecn.htm"><span style="font-style:italic;">Explicit Congestion Notification (ECN)</span></a>, su <span style="font-style:italic;">msxfaq.de</span>.</cite></li></ul> <div class="noprint" style="width:100%; padding: 3px 0; display: flex; flex-wrap: wrap; row-gap: 4px; column-gap: 8px; box-sizing: border-box;"><div style="flex-grow: 1"><style data-mw-deduplicate="TemplateStyles:r140555418">.mw-parser-output .itwiki-template-occhiello{width:100%;line-height:25px;border:1px solid #CCF;background-color:#F0EEFF;box-sizing:border-box}.mw-parser-output .itwiki-template-occhiello-progetto{background-color:#FAFAFA}@media screen{html.skin-theme-clientpref-night .mw-parser-output .itwiki-template-occhiello{background-color:#202122;border-color:#54595D}html.skin-theme-clientpref-night .mw-parser-output .itwiki-template-occhiello-progetto{background-color:#282929}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .itwiki-template-occhiello{background-color:#202122;border-color:#54595D}html.skin-theme-clientpref-os .mw-parser-output .itwiki-template-occhiello-progetto{background-color:#282929}}</style><div class="itwiki-template-occhiello"><span class="noviewer" typeof="mw:File"><a href="/wiki/File:Crystal_128_displayphone.png" class="mw-file-description" title="Telematica"><img alt=" " src="//upload.wikimedia.org/wikipedia/commons/thumb/4/46/Crystal_128_displayphone.png/24px-Crystal_128_displayphone.png" decoding="async" width="24" height="25" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/4/46/Crystal_128_displayphone.png/37px-Crystal_128_displayphone.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/4/46/Crystal_128_displayphone.png/49px-Crystal_128_displayphone.png 2x" data-file-width="124" data-file-height="127" /></a></span> <b><a href="/wiki/Portale:Telematica" title="Portale:Telematica">Portale Telematica</a></b>: accedi alle voci di Wikipedia che parlano di reti, telecomunicazioni e protocolli di rete</div></div></div>    </div><noscript><img src="https://login.wikimedia.org/wiki/Special:CentralAutoLogin/start?useformat=desktop&type=1x1&usesul3=0" alt="" width="1" height="1" style="border: none; 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