Hi Thomas, In this particular case, I don't think we should do anything to the document. In the general case, I'm often leary of overloading something that is meant to be opaque with meaning, as it tends to be an attractive nuisance for other folks, who try to extract that meaning or cause behavior by acting on the overloaded arbitrary data. regards, Ted
Can you expand? I don't understand the concern. The basic idea here is that the "abitrary data" is internal state of the sender. No one else uses that data (or parses it) it is simply echoed back in the response traffic, allowing the relaying device to insert state about the "request response pair" in the message and then extract it from the response. This allows it to put the state in the message rather than on the device (i.e, devices are more stateless). Thomas