Path MTU Discovery
Path MTU Discovery
- Send out large packets with DF (Don’t Fragment) bit set in IP header
- Routers which transition to a lower MTU technology (i.e. FDDI to Ethernet) must send back an ICMP “Can’t Fragment” message. Bridges should do this, too!
- Host then reduces MTU to a value specified by the router.
- Iterate until Path MTU is known.