If you create/maintain the software that implements “tunnel endpoints” on IP routers, please (pretty, pretty please - with a cherry on top) act on the suggestions below!
Your in-network-tunneling devices are both “routers” and “hosts” (please behave accordingly)
- Maintain PMTUD state on Tu interfaces for destinations on the underlays (host behavior)
- Generate PTBs when an overlay packet can’t be encapped and sent to the underlay (router behavior)
- Include the Tu interface’s path MTU when making the determination about whether MTU would be exceeded