okay...slightly different use of terminology.
insisting on IPP using port 80 just to be able to tunnel through
firewalls/proxies simply will not fly ...it leads to an arms race.
(not to mention that everybody will want to use port 80, which
is clearly unworkable)
if your employer wants you to be able to use external printers,
they can punch a hole in their firewall, or add a proxy, to
allow you to talk to the default IPP port.
we can't let the existence of NAT boxes dictate the whole architecture.