https://nalar.dev/tags/packets/ Recent content in Packets on Nalar Hugo en-us Wed, 16 Sep 2026 00:00:00 +0700 https://nalar.dev/path-mtu-discovery-finds-packet-size-limits/ Wed, 16 Sep 2026 00:00:00 +0700 https://nalar.dev/path-mtu-discovery-finds-packet-size-limits/ <p>Every network link has a maximum transmission unit, or MTU, that limits the size of an IP packet carried in one link-layer frame. A route can cross links with different limits, so the smallest relevant MTU along that route constrains packet size end to end.</p> <p>Path MTU Discovery, commonly shortened to PMTUD, lets an endpoint find that constraint and adjust packet sizes rather than relying on fragmentation.</p> <h2 id="one-route-can-contain-several-mtu-limits">One route can contain several MTU limits</h2> <p>Ethernet commonly uses an IP MTU of 1500 bytes, but tunnels, VPNs, encapsulation, and other link types can reduce the usable size. A packet that fits the sender&rsquo;s local interface can therefore be too large for a later hop.</p>