> Any new METHOD in HTTP is a serious modification to the protocol, because
> the forwarding function must be aware of it. A new content-type, however,
> can be as easily recognized in the filter layer as a new method, but
> requires NO changes to the forwarding function. Many filters already filter
> on content-type anyway.
But will the content-type be ok in both directions? What is the
content-type of an ipp response? If it is not also application/ipp,
then you could easily create a situation in which the request can be
sent and pass through the filter, but the response cannot...