Printing from cupsd to cupsd via an internet link: Where thefilters are applied

[Sebastian James]

> Sebastian James wrote:
> > Hi CUPSers,
> >
> > We've been using cups to print across a WAN link for quite a while now. It works well.
> >
> > cupsd_1 receives a print job, then sends it using the https method over the WAN to cupsd_2 which then forwards it on to a printer.
> >
> > If the incoming print job needs to be converted using the CUPS filtering system into a suitable format for the printer at the end of the chain, then the filtering HAS to happen at cupsd_1, as far as I can tell.
> >
> > This is not always a good thing, because we generally end up transferring _more_ data across the link. For example, if the incoming job is a PDF file, then converting it into postscript suitable for an HP Laserjet printer leads to a _lot more_ data to transfer.
> >
> > It seems that the ipp protocol or at least cups' implementation of it means that data that is sent via ipp or its encrypted version, https is considered "finished".
> >
> > It would be great if it were possible to set a parameter in cupsd.conf to say "always apply file-typing heuristics and CUPS filtering to incoming jobs".
> >
> > Would this feature be a major problem? I would like to implement it.
> >
> > very best regards,
> >
> > Seb James
>
> I had a similar problem with my Mac OS X laptop which connects to my company's network via an
> UMTS/HSPA link. As this suffers similarly from the size of the print kobs transferred,
> I did the following workaround:
> (1) I downloaded the fully configured PPD from the print server and installed
>      the printer locally but using ipp://printserver/printers/printername as
>      DEVICE_URI
> (2) Then I deleted the /etc/cups/ppd/printername.ppd on the local machind
>      and restarted the local CUPSD.
>
> Thus I have a permanently installed printer which behaves exactly as
> an imported printer (e.g. by CUPS browsing or polling).
>
> I'd suggest to gibe that a try, especially as - provided your WAN link is up - you
> even are able to administer the remote printer.
>
> Helge
>

Interesting - so when the print jobs arrives at the local cupsd, it finds no ppd, so treats it as raw locally. It then forwards the data to the company server, where the ppd is applied.

Thanks for the pointer; I didn't realise you could do that to force "ppd filtering" at the receiving end. I'll give it a try.

That said, I _would_ still like to be able to apply a filter at _both_ ends of the chain. For example, I might wish to do some custom logging for both the sending and receiving of the print data, as well as doing the data conversion into a page description language ready for the printer.

Many thanks for your reply!

Seb James