[cups.general] An idea how to provide CUPS Browsing for CUPS 1.6

Michael Sweet msweet at apple.com
Thu Nov 22 11:00:12 PST 2012


On 2012-11-22, at 6:58 AM, Johannes Meixner <jsmeix at suse.de> wrote:
> Hello,
> this is a request for comments if and how it might be possible
> to provide CUPS Browsing for CUPS 1.6.
> Since CUPS 1.6 the source code that implements CUPS Browsing
> does no longer exist.
> Michael Sweet explained why CUPS Browsing is no longer
> supported by Apple's CUPS.
> As far as I understand from the information that I have
> it seems the background reason why Apple dropped so many
> things in CUPS 1.6 is that Apple does no longer want to
> maintain code in CUPS that is neither used nor tested by Apple.
> If my understanding is right, I would perfectly agree with such
> a decision.

FWIW, Apple has not relied on CUPS browsing in OS X since 10.4, but that is only one (minor) reason why it was dropped.

CUPS browsing has a number of technical issues that cannot be resolved:

1. Name resolution; servers need to have registered hostnames, static IPs, or some sort of sync'd hosts file setup.

2. Routing issues: browsing only works on local subnets, relay doesn't work for link-local addresses

3. Broadcast issues: broadcast packets do bad things to Wi-Fi networks, and are often blocked on managed networks.

4. No IPv6 support.

5. You need a process around that listens for printers coming and going all of the time (battery, CPU, memory usage)

6. It takes two cycles (60 seconds with the default browse interval) to recover the printer list after waking from sleep.

As for the transition, there have been Avahi patches for CUPS since 1.4, and while those finally made it into 1.6 they have been included in many (most?) Linux distributions for a long time.

Michael Sweet, Senior Printing System Engineer, PWG Chair

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