Canon MG5520 wireless printer

[Tim]

On Sat, 2014-10-11 at 21:26 -0400, Kevin Cummings wrote:
> When I started the Print Settings tool, I had to unlock it first, then
> I started the ADD PRINTER dialogue.  When it prompted to select
> device, I opened the Network Printer expansion, but the printer I was
> looking for was not present, so I decided to enter it manually.  While
> I was trying to figure out how to do that, an entry for the printer
> "magically" appeared in the network list!  I guess it took a little
> time to "find" it.

My experience with these kind of things (auto discovery of things on a
network), is that there is nearly always some sort of delay (either
you're waiting for periodic announcement of available things on the net,
or waiting for things to reply to a request of what's out there), but I
have never managed to find anything that defines what the delay will be,
nor why?  Was it simply call and response time (didn't seem likely, as
the period could be a few seconds to minutes), or was there a periodic
announcement, with a random or defined period?

With CUPS, at least, it was necessary to have a hole in your firewall to
receive these announcements (the IPP *service* needed to be allowed).
I'd imagine a similar requirement for ZeroConf, Avahi, or any other
auto-discovery process.  It's all peer-to-peer, not run by a central
server  (unless you're using Samba, which has a semi-random server), so
you have to have a hole open and waiting, all the time.

If there was a central server, you wouldn't need to, your client would
make a request, and get a reply.  That reply would be *related* to your
query, and would (should?) automatically make it back through your
firewall, without requiring special configuration (normal firewall
configuration is to *allow* *related* traffic through).


-- 
tim at localhost ~]$ uname -rsvp

Linux 3.16.3-200.fc20.i686 #1 SMP Wed Sep 17 23:07:44 UTC 2014 i686

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