Hi Yoshi, thank you very much for your thoughtful review. For now, let me pick one of your comments: > 3: Since this draft defines new SZX value, I think the doc needs to update RFC7959. This point should be clarified more in the doc. The spec does indeed define a new SZX value, for use with the environments this document is used in (reliable transports). It does not change or add anything to the way RFC 7959 is used with the existing unreliable transports; as such it does not really update RFC 7959 as much as it does extend it for its own purposes. (However, the same argument could be made for RFC 7641, which we do say we update.) Maybe we are not making the point forcefully enough that SZX=7 is meant for use within this spec? (Again, however: any other future COAP transports that have larger messages might pick up SZX=7 as well.) I don’t have a strong opinion on how to populate the “updates” graph of RFCs in these boundary cases; it might help to get some more guidance here. Grüße, Carsten