diff --git a/README.md b/README.md
index d0a97a8..54ee51a 100644
--- a/README.md
+++ b/README.md
@@ -7,7 +7,7 @@ Minitel aims to implement layers 3, 4 and 5 of the OSI model.
 
 
 ## Layers
-![Layer organisation in Minitel](img/minitel-layers.png)
+![Layer organisation in Minitel](img/minitel-layers.svg)
 ### Layer 3
 [Layer 3](protocol-3.md) implements addressing, meshing and datagram transmission.
 
diff --git a/img/minitel-layers.png b/img/minitel-layers.png
deleted file mode 100644
index 8e08d96..0000000
Binary files a/img/minitel-layers.png and /dev/null differ
diff --git a/img/minitel-layers.svg b/img/minitel-layers.svg
new file mode 100644
index 0000000..9e93af5
--- /dev/null
+++ b/img/minitel-layers.svg
@@ -0,0 +1,2 @@
+<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
+<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="281px" height="281px" version="1.1" content="&lt;mxfile userAgent=&quot;Mozilla/5.0 (X11; Linux x86_64; rv:62.0) Gecko/20100101 Firefox/62.0&quot; version=&quot;9.2.8&quot; editor=&quot;www.draw.io&quot; type=&quot;device&quot;&gt;&lt;diagram id=&quot;75ccc015-4e13-2a57-4753-fe7075901d7a&quot; name=&quot;Page-1&quot;&gt;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&lt;/diagram&gt;&lt;/mxfile&gt;"><defs><linearGradient x1="0%" y1="0%" x2="0%" y2="100%" id="mx-gradient-d8ec9b-1-e7ed9c-1-s-0"><stop offset="0%" style="stop-color:#d8ec9b"/><stop offset="100%" style="stop-color:#E7ED9C"/></linearGradient><linearGradient x1="0%" y1="0%" x2="0%" y2="100%" id="mx-gradient-e7ed9c-1-eddc9c-1-s-0"><stop offset="0%" style="stop-color:#e7ed9c"/><stop offset="100%" style="stop-color:#eddc9c"/></linearGradient></defs><g transform="translate(0.5,0.5)"><rect x="40" y="0" width="120" height="40" fill="#d8ec9b" stroke="#000000" pointer-events="none"/><g transform="translate(66.5,13.5)"><switch><foreignObject style="overflow:visible;" pointer-events="all" width="67" height="12" requiredFeatures="http://www.w3.org/TR/SVG11/feature#Extensibility"><div xmlns="http://www.w3.org/1999/xhtml" style="display: inline-block; font-size: 12px; font-family: Helvetica; color: rgb(0, 0, 0); line-height: 1.2; vertical-align: top; width: 68px; white-space: nowrap; overflow-wrap: normal; text-align: center;"><div xmlns="http://www.w3.org/1999/xhtml" style="display:inline-block;text-align:inherit;text-decoration:inherit;">syslog, RPC</div></div></foreignObject><text x="34" y="12" fill="#000000" text-anchor="middle" font-size="12px" font-family="Helvetica">syslog, RPC</text></switch></g><rect x="160" y="0" width="120" height="40" fill="#d8ec9b" stroke="#000000" pointer-events="none"/><g transform="translate(173.5,13.5)"><switch><foreignObject style="overflow:visible;" pointer-events="all" width="92" height="12" requiredFeatures="http://www.w3.org/TR/SVG11/feature#Extensibility"><div xmlns="http://www.w3.org/1999/xhtml" style="display: inline-block; font-size: 12px; font-family: Helvetica; color: rgb(0, 0, 0); line-height: 1.2; vertical-align: top; width: 93px; white-space: nowrap; overflow-wrap: normal; text-align: center;"><div xmlns="http://www.w3.org/1999/xhtml" style="display:inline-block;text-align:inherit;text-decoration:inherit;">FRequest, MMail</div></div></foreignObject><text x="46" y="12" fill="#000000" text-anchor="middle" font-size="12px" font-family="Helvetica">FRequest, MMail</text></switch></g><rect x="160" y="80" width="120" height="60" fill="url(#mx-gradient-d8ec9b-1-e7ed9c-1-s-0)" stroke="#000000" pointer-events="none"/><g transform="translate(178.5,103.5)"><switch><foreignObject style="overflow:visible;" pointer-events="all" width="82" height="12" requiredFeatures="http://www.w3.org/TR/SVG11/feature#Extensibility"><div xmlns="http://www.w3.org/1999/xhtml" style="display: inline-block; font-size: 12px; font-family: Helvetica; color: rgb(0, 0, 0); line-height: 1.2; vertical-align: top; width: 83px; white-space: nowrap; overflow-wrap: normal; text-align: center;"><div xmlns="http://www.w3.org/1999/xhtml" style="display:inline-block;text-align:inherit;text-decoration:inherit;">Minitel streams</div></div></foreignObject><text x="41" y="12" fill="#000000" text-anchor="middle" font-size="12px" font-family="Helvetica">Minitel streams</text></switch></g><rect x="40" y="140" width="240" height="60" fill="url(#mx-gradient-e7ed9c-1-eddc9c-1-s-0)" stroke="#000000" pointer-events="none"/><g transform="translate(119.5,163.5)"><switch><foreignObject style="overflow:visible;" pointer-events="all" width="80" height="12" requiredFeatures="http://www.w3.org/TR/SVG11/feature#Extensibility"><div xmlns="http://www.w3.org/1999/xhtml" style="display: inline-block; font-size: 12px; font-family: Helvetica; color: rgb(0, 0, 0); line-height: 1.2; vertical-align: top; width: 81px; white-space: nowrap; overflow-wrap: normal; text-align: center;"><div xmlns="http://www.w3.org/1999/xhtml" style="display:inline-block;text-align:inherit;text-decoration:inherit;">Minitel Layer 3</div></div></foreignObject><text x="40" y="12" fill="#000000" text-anchor="middle" font-size="12px" font-family="Helvetica">Minitel Layer 3</text></switch></g><rect x="40" y="200" width="240" height="40" fill="#e9c189" stroke="#000000" pointer-events="none"/><g transform="translate(92.5,213.5)"><switch><foreignObject style="overflow:visible;" pointer-events="all" width="135" height="12" requiredFeatures="http://www.w3.org/TR/SVG11/feature#Extensibility"><div xmlns="http://www.w3.org/1999/xhtml" style="display: inline-block; font-size: 12px; font-family: Helvetica; color: rgb(0, 0, 0); line-height: 1.2; vertical-align: top; width: 136px; white-space: nowrap; overflow-wrap: normal; text-align: center;"><div xmlns="http://www.w3.org/1999/xhtml" style="display:inline-block;text-align:inherit;text-decoration:inherit;">OpenComputers packets</div></div></foreignObject><text x="68" y="12" fill="#000000" text-anchor="middle" font-size="12px" font-family="Helvetica">OpenComputers packets</text></switch></g><rect x="40" y="240" width="240" height="40" fill="#e9988a" stroke="#000000" pointer-events="none"/><g transform="translate(87.5,253.5)"><switch><foreignObject style="overflow:visible;" pointer-events="all" width="145" height="12" requiredFeatures="http://www.w3.org/TR/SVG11/feature#Extensibility"><div xmlns="http://www.w3.org/1999/xhtml" style="display: inline-block; font-size: 12px; font-family: Helvetica; color: rgb(0, 0, 0); line-height: 1.2; vertical-align: top; width: 146px; white-space: nowrap; overflow-wrap: normal; text-align: center;"><div xmlns="http://www.w3.org/1999/xhtml" style="display:inline-block;text-align:inherit;text-decoration:inherit;">OpenComputers hardware</div></div></foreignObject><text x="73" y="12" fill="#000000" text-anchor="middle" font-size="12px" font-family="Helvetica">OpenComputers hardware</text></switch></g><rect x="0" y="0" width="40" height="40" fill="#d8ec9b" stroke="#000000" pointer-events="none"/><g transform="translate(16.5,13.5)"><switch><foreignObject style="overflow:visible;" pointer-events="all" width="7" height="12" requiredFeatures="http://www.w3.org/TR/SVG11/feature#Extensibility"><div xmlns="http://www.w3.org/1999/xhtml" style="display: inline-block; font-size: 12px; font-family: Helvetica; color: rgb(0, 0, 0); line-height: 1.2; vertical-align: top; width: 8px; white-space: nowrap; overflow-wrap: normal; text-align: center;"><div xmlns="http://www.w3.org/1999/xhtml" style="display:inline-block;text-align:inherit;text-decoration:inherit;">7</div></div></foreignObject><text x="4" y="12" fill="#000000" text-anchor="middle" font-size="12px" font-family="Helvetica">7</text></switch></g><rect x="0" y="40" width="40" height="40" fill="#d8ec9b" stroke="#000000" pointer-events="none"/><g transform="translate(16.5,53.5)"><switch><foreignObject style="overflow:visible;" pointer-events="all" width="7" height="12" requiredFeatures="http://www.w3.org/TR/SVG11/feature#Extensibility"><div xmlns="http://www.w3.org/1999/xhtml" style="display: inline-block; font-size: 12px; font-family: Helvetica; color: rgb(0, 0, 0); line-height: 1.2; vertical-align: top; width: 8px; white-space: nowrap; overflow-wrap: normal; text-align: center;"><div xmlns="http://www.w3.org/1999/xhtml" style="display:inline-block;text-align:inherit;text-decoration:inherit;">6</div></div></foreignObject><text x="4" y="12" fill="#000000" text-anchor="middle" font-size="12px" font-family="Helvetica">6</text></switch></g><rect x="0" y="80" width="40" height="40" fill="#d8ec9b" stroke="#000000" transform="rotate(90,20,100)" pointer-events="none"/><g transform="translate(16.5,93.5)"><switch><foreignObject style="overflow:visible;" pointer-events="all" width="7" height="12" requiredFeatures="http://www.w3.org/TR/SVG11/feature#Extensibility"><div xmlns="http://www.w3.org/1999/xhtml" style="display: inline-block; font-size: 12px; font-family: Helvetica; color: rgb(0, 0, 0); line-height: 1.2; vertical-align: top; width: 8px; white-space: nowrap; overflow-wrap: normal; text-align: center;"><div xmlns="http://www.w3.org/1999/xhtml" style="display:inline-block;text-align:inherit;text-decoration:inherit;">5</div></div></foreignObject><text x="4" y="12" fill="#000000" text-anchor="middle" font-size="12px" font-family="Helvetica">5</text></switch></g><rect x="0" y="120" width="40" height="40" fill="#e7ed9c" stroke="#000000" pointer-events="none"/><g transform="translate(16.5,133.5)"><switch><foreignObject style="overflow:visible;" pointer-events="all" width="7" height="12" requiredFeatures="http://www.w3.org/TR/SVG11/feature#Extensibility"><div xmlns="http://www.w3.org/1999/xhtml" style="display: inline-block; font-size: 12px; font-family: Helvetica; color: rgb(0, 0, 0); line-height: 1.2; vertical-align: top; width: 8px; white-space: nowrap; overflow-wrap: normal; text-align: center;"><div xmlns="http://www.w3.org/1999/xhtml" style="display:inline-block;text-align:inherit;text-decoration:inherit;">4</div></div></foreignObject><text x="4" y="12" fill="#000000" text-anchor="middle" font-size="12px" font-family="Helvetica">4</text></switch></g><rect x="0" y="160" width="40" height="40" fill="url(#mx-gradient-e7ed9c-1-eddc9c-1-s-0)" stroke="#000000" pointer-events="none"/><g transform="translate(16.5,173.5)"><switch><foreignObject style="overflow:visible;" pointer-events="all" width="7" height="12" requiredFeatures="http://www.w3.org/TR/SVG11/feature#Extensibility"><div xmlns="http://www.w3.org/1999/xhtml" style="display: inline-block; font-size: 12px; font-family: Helvetica; color: rgb(0, 0, 0); line-height: 1.2; vertical-align: top; width: 8px; white-space: nowrap; overflow-wrap: normal; text-align: center;"><div xmlns="http://www.w3.org/1999/xhtml" style="display:inline-block;text-align:inherit;text-decoration:inherit;">3</div></div></foreignObject><text x="4" y="12" fill="#000000" text-anchor="middle" font-size="12px" font-family="Helvetica">3</text></switch></g><rect x="0" y="200" width="40" height="40" fill="#e9c189" stroke="#000000" pointer-events="none"/><g transform="translate(16.5,213.5)"><switch><foreignObject style="overflow:visible;" pointer-events="all" width="7" height="12" requiredFeatures="http://www.w3.org/TR/SVG11/feature#Extensibility"><div xmlns="http://www.w3.org/1999/xhtml" style="display: inline-block; font-size: 12px; font-family: Helvetica; color: rgb(0, 0, 0); line-height: 1.2; vertical-align: top; width: 8px; white-space: nowrap; overflow-wrap: normal; text-align: center;"><div xmlns="http://www.w3.org/1999/xhtml" style="display:inline-block;text-align:inherit;text-decoration:inherit;">2</div></div></foreignObject><text x="4" y="12" fill="#000000" text-anchor="middle" font-size="12px" font-family="Helvetica">2</text></switch></g><rect x="0" y="240" width="40" height="40" fill="#e9988a" stroke="#000000" pointer-events="none"/><g transform="translate(16.5,253.5)"><switch><foreignObject style="overflow:visible;" pointer-events="all" width="7" height="12" requiredFeatures="http://www.w3.org/TR/SVG11/feature#Extensibility"><div xmlns="http://www.w3.org/1999/xhtml" style="display: inline-block; font-size: 12px; font-family: Helvetica; color: rgb(0, 0, 0); line-height: 1.2; vertical-align: top; width: 8px; white-space: nowrap; overflow-wrap: normal; text-align: center;"><div xmlns="http://www.w3.org/1999/xhtml" style="display:inline-block;text-align:inherit;text-decoration:inherit;">1</div></div></foreignObject><text x="4" y="12" fill="#000000" text-anchor="middle" font-size="12px" font-family="Helvetica">1</text></switch></g></g></svg>
\ No newline at end of file