A small update to this older thread:
DNS-SD would certainly be useful for automatic printer discovery and easier setup. However, discovery and printing are two separate parts of the problem.
As PulkoMandy explained above, Haiku’s existing IPP transport uses its own rather broken HTTP implementation. This means that printing may still fail even when the printer address, port 631 and the correct IPP queue are already known.
I recently approached the problem from the Linux side and looked at what is actually sent to an IPP printer on port 631. Based on that, I developed an experimental userspace workaround called Haiku IPP Print Bridge.
The bridge currently works without DNS-SD. The printer address and queue are entered manually, and it sends a proper IPP Print-Job request directly to the printer. PDF and PostScript files are converted to JPEG pages with Ghostscript before being submitted.
It has been tested successfully with Brother printers, and another user has successfully printed a test page on an HP Envy printer from Haiku hrev59048.
So DNS-SD would improve convenience and automatic discovery, while a working and compatible IPP/HTTP transport is still required for the actual print job.
Project and discussion:
Greetz & THX
Juergen