https://songkou.github.io/tags/network/Recent content in Network on Council of ElrondHugoenSat, 11 Jul 2026 07:00:00 +0800https://songkou.github.io/posts/how_linux_sends_and_receives_network_packets/Sat, 11 Jul 2026 07:00:00 +0800https://songkou.github.io/posts/how_linux_sends_and_receives_network_packets/<blockquote> <p>Study notes rewritten in my own words</p> </blockquote> <h2 id="network-models">Network models</h2> <p>To let all kinds of devices talk to each other over a network, the ISO defined the <strong>OSI reference model</strong> with 7 layers. Each layer has a single job:</p> <ul> <li><strong>Application</strong> – provides a uniform interface to programs</li> <li><strong>Presentation</strong> – converts data into a format another system understands</li> <li><strong>Session</strong> – establishes, manages and terminates sessions</li> <li><strong>Transport</strong> – end-to-end data transfer</li> <li><strong>Network</strong> – routing, forwarding, fragmentation</li> <li><strong>Data link</strong> – framing, error detection, MAC addressing</li> <li><strong>Physical</strong> – transmits frames over the physical medium</li> </ul> <p>OSI is mostly a <em>conceptual</em> model — it never shipped a concrete implementation. What we actually use is the simpler <strong>TCP/IP model</strong> with 4 layers, and the Linux stack is built to match it:</p>