Re: Semi-OT: IPP doesn't auto-configure CUPS?
On Mon 11 Nov 2019 at 14:02:50 -0600, Kent West wrote:
> I've been trying to wrap my head around printing today, and I have come to
> understand that IPP is the up-and-coming standard for printing (replacing
> the older LPD / AppSocket / HP Jet Direct / etc), and more specifically,
> that IPPEverywhere is the new and up-and-coming standard (of which Apple's
> AirPrint is a variant/extension, more broadly-supported simply by being
> older, although not fully documented as is the newer IPPEverywhere).
More or less. But bear in mind that CUPS has always been based on
IPP. What has changed in the past ten years is that almost all modern
printers now come with decent IPP implementations and offer an AirPrint
service.
> It is further my understanding that IPP is supposed to query the printer for
> its capabilities (double-sided printing? stapling? A4 paper size in the
> tray, etc).
Ok.
> It is further my understanding that IPP can (does?) query the printer for
> this info just prior to each print job.
Not quite. The applications (Firefox, LibreOffice etc) get the printer
attributes when their dialogs are opened.
> But I also thought that IPP would query the printer for this info when the
> printer is added to the client PC. I find that to not be the case, however,
> on my Debian Bullseye/sid box, and on a Mac Catalina MacBook. Am I incorrect
> about this setup-time polling?
No. You are correct.
> What I mean more specifically is, when I go into the CUPS web interface to
> set up a new printer, and go through the Add Printer stuff, and select
> "Other Network Printers" / "Internet Printing Protocol (ipps)" (because the
> printer is on a different subnet/virtual LAN and therefore doesn't get
> autodetected via Bonjour/mDNS/DNS-SD), and then on the next screen enter the
> IP address of the printer, I would have expected the IPP protocol to then
> handle the rest of the printer setup, but instead I'm still asked for the
> printer name and printer model (although I just now noticed that what is
> currently selected (I'm not sure it was when I started this email) is
> "{current_make_and_model} - IPP Everywhere" - perhaps this option is doing
> what I was expecting?).
How does IPP know that you intend calling the printer destination
"charles"?
> (If I select that IPP Everywhere option, the next screen errors out saying
> "Unable to open PPD file: Missing asterisk in column 1", so I suspect that
> option is not doing what I was expecting.)
This is CUPS' way of telling you that an ipps service is not offered by
the printer. With lpadmin you would get "An unexpected TLS packet was
received".
--
Brian.
Reply to: