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<title>Introduzione alle reti</title>


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    <section><h3 id="intro-sulle-reti">intro sulle reti</h3>
</section><section>
<h3 id="come-funziona-linternet">Come funziona l&rsquo;internet?</h3>
</section><section>
<ul>
<li>via radio</li>
<li>con le antenne telefoniche</li>
<li>con cavi sottomarini</li>
<li>con connessioni satellitari</li>
</ul>
</section><section>
<h5 id="heading"></h5>
<p><img src="../images/cable_map.png" alt="/images/cable_map.png"></p>
</section><section>
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<h3 id="un-po-di-sigle">Un po di sigle</h3>
<p>Tanto per confonderci meglio, cerchiamo di capire cosa fanno questi diversi
elementi</p>
</section><section>
<ul>
<li>ISP</li>
<li>Router</li>
<li>WAN</li>
<li>LAN</li>
<li>Host(s)</li>
<li>WLAN</li>
</ul>
</section><section>
<h3 id="stack-isoosi">Stack ISO/OSI</h3>
<p>Possiamo dividere la rete internet, per come viene vista da un pacchetto,
si puo&rsquo; suddividere in sette &ldquo;strati&rdquo;.</p>
</section><section>
<img src='../images/iso.png' style='height: 600px;'/>
</section><section>
<h3 id="dallalto-verso-il-basso">Dall&rsquo;alto verso il basso</h3>
<p><strong>Application Layer</strong></p>
<ul>
<li>HTTP (Hypertext Transfer Protocol)</li>
<li>SMTP (Simple Mail Transfer Protocol)</li>
</ul>
<p>ce ne sono un sacco, ma chi decide? <a href="https://datatracker.ietf.org/doc/html/rfc2616">RFC</a>, IETF</p>
</section><section>
<h3 id="transport-layer">Transport Layer</h3>
<p>Come i dati vengono mandati, se controllando o meno gli errori durante la
connessione.</p>
<ul>
<li>TCP (Transmission Control Protocol) - reliable data delivery</li>
<li>UDP (User Datagram Protocol) - unreliable data delivery</li>
</ul>
</section><section>
<h3 id="network-layer">Network Layer</h3>
<p>Qui per permettere agli host, più propriamente al sistema operativo,</p>
<p>Questo layer usa:</p>
<ul>
<li>IP (Internet Protocol) - Permette di instradare pacchetti da una host
all&rsquo;altro</li>
<li>ICMP (Internet Control Message Protocol) - Errori, debug, che succede.</li>
</ul>
</section><section>
<h3 id="link-layer">Link Layer</h3>
<p>Come vengono mandati fisicamente i dati nella ferraglia</p>
<ul>
<li>quanti modi vi vengono in mente?</li>
</ul>
</section><section>
<h3 id="paccheti-che-si-instradano">Paccheti che si instradano?</h3>
<p>Abbiamo trovato un modo molto criptico di dire &ldquo;dati che si muovono&rdquo;, ma
avviene cio'?</p>
<ul>
<li>MAC: 8 byte OUI (Organizational unique identifier) 8 univoci per scheda
fisica</li>
<li>IP</li>
<li>Hostname</li>
</ul>
</section><section>
<h3 id="quindi-se-visito-un-sito-che-giro-faccio">Quindi, se visito un sito, che giro faccio?</h3>
</section><section>
<h3 id="layer-applicativo">Layer Applicativo</h3>
<pre><code>* Protocollo HTTP
* Metodi: GET, POST, vari ed eventuali
&gt; GET / HTTP/1.1
&gt; Host: google.com
</code></pre>
</section><section>
<h3 id="layer-di-trasporto">Layer di trasporto</h3>
<pre><code>- Porte
- UDP
- TCP
</code></pre>
</section><section>
<h3 id="layer-di-rete">Layer di Rete</h3>
<pre><code>- IP: destinazione e sorgente
</code></pre>
</section><section>
<h3 id="layer-fisico">Layer Fisico</h3>
<pre><code>- Incapsula il pacchetto TCP/IP dentro un frame
- ARP (Address Resolution Protocol)
</code></pre>
</section><section>
<h3 id="quindi-se-vado-su-un-sito-che-giro-faccio">Quindi se vado su un sito che giro faccio?</h3>
<p><img src="../images/stackiso.png" alt="Esempio stack ISO/OSI"></p>
</section><section>
<h3 id="route-netmask-e-altre-cose-orribili">ROUTE, NETMASK, E ALTRE COSE ORRIBILI</h3>
<ul>
<li>Ovvero, di cosa ha bisogno il mio computer per attaccarsi al router?</li>
<li>IP, lo abbiamo visto</li>
<li>GATEWAY, &ldquo;da dove passare&rdquo;, quindi l&rsquo;IP del gateway</li>
<li>NETMASK, il mio PC sa di essere in una sottorete, ma quanto e'
grande?</li>
</ul>
<p>Con questi ingredienti posso collegarmi al router!</p>
</section><section>
<h3 id="dhcp">DHCP</h3>
<p>E&rsquo; interessante cercare di capire come fa il router a farci collegare
in automatico.</p>
<ul>
<li>DHCP</li>
<li>DHCP DISCOVER</li>
<li>DHCP OFFER</li>
<li>DHCP REQUEST</li>
<li>DHCP ACK</li>
<li>Riusciamo a vederlo con wireshark?</li>
</ul>
</section><section>
<h3 id="http">HTTP</h3>
<p>Proviamo! Posso usare internet da terminale?</p>
<p><code>curl https://www.wttr.in/turin </code></p>
</section><section>
<h3 id="developer-tools">Developer Tools</h3>
<p>Ovvero, avevate mai provato a premere <strong>F12</strong> sul browser?</p>
</section><section>
<h3 id="get">GET</h3>
<ul>
<li>parametri</li>
<li>escaping</li>
<li>content-type</li>
</ul>
<p>eg. autocompletamento di startpage.com</p>
</section><section>
<h3 id="post">POST</h3>
<ul>
<li>parametri</li>
<li>dati</li>
</ul>
</section><section>
<h3 id="live---ws">Live - WS</h3>
<p>pad.</p>
</section>

  
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