4 ms·

> One final note: If as a router or application developer you ever find yourself having to fragment packets, Ideally, you should not want to fragment IP packet

> One final note: If as a router or application developer you ever find yourself having to fragment packets, Ideally, you should not want to fragment IP packets. It is far better to do MSS clamping in TCP to prevent the size of the TCP payload to grew above the size of the max MTU in the path. TCP can stitch together the data at the other node just fine, without routers in between having to fragment the IP packets, which will kill your bandwith in comparison.

jandrese 6y ago
The "application" in this case is for example a packet->radio bridge application, or a VPN tunnel endpoint. Something that is chewing on packets mid stream where you don't get much choice in the matter. One thing I like about IPv6 is the minimum MTU of 1280. That's big enough that if I'm really uncertain about the environment I can just set my MTU to that and avoid future headaches without impacting performance too badly. IPv4's 576 minimum nearly triples the number of packets you generate, which is really noticeable when you're running routers close to their limit. Forwarding speed is often dominated by packets per second, not bytes per second.
- garaetjjte 6y ago
  >IPv4's 576 minimum nearly triples the number of packets you generate IPv4 minimum MTU is... 68 bytes. >Every internet module must be able to forward a datagram of 68 octets without further fragmentation. https://tools.ietf.org/html/rfc791 https://tools.ietf.org/html/rfc791