On May 2, 2017, at 07:31, weigengyu <weigengyu@xxxxxxxxxxx> wrote: > > The problem is when the C2C Proxy have got a message form the CoAP/TCP side, > how the Proxy make a decision to delivery CON or NON message carrying CoAP over UDP? The question is not very different from the UDP to UDP proxying case. If a request came in via a UDP CON (which is the equivalent of using a reliable transport protocol), should the proxy use CON or NON for the forwarded request? I’d say, in both cases, CON should be the default way of forwarding the reliable request. But there may be specific cases where a NON may be appropriate — CoAP does not provide the client with a way to control the proxy here. Is that a problem? Tell me more about your use case. Grüße, Carsten