In the previous post on MSS, MSS Clamping, PMTUD, and MTU, we learned how PMTUD is performed by setting the Don’t fragment flag in the IP header which leads to the device that needs to perform fragmentation dropping the packet
IP fragmentation
Every physical medium has a maximum size of packets it can send. This is called MTU (Maximum Transmission Unit). For Ethernet this is usually 1500 bytes. If we send packets that are larger than 1500 bytes fragmentation is needed. Fragmentation