I'd like to ask you a question on Capabilities Update when 'relay' nodes are concerned. Specifically, I want to ask whether 'relay' nodes need to advertise the Capabilities Update App Id (10) alongside 0xffffffff
towards adjacent diameter nodes or not.
Consider a case where proxy agent A is connected to relay agent B, and A wants to update its supported applications.
If B has not advertised 10 in the initial CER / CEA exchange (alongside 0xffffffff), how can A know if B implements RFC6737? Should A try a Capabilities Update nevertheless and, in case that RFC 6737 is not implemented, just get a DIAMETER_APPLICATION_UNSUPPORTED error back?
The above issue could be fixed if the Capabilities Update App Id is sent alongside 0xffffffff in the initial capabilities exchange handshake, but it feels a little bit strange, since 0xffffffff implies 'all applications'.