wireless printers hang

[Dave Chamberlin]

I have an N4000 running HPUX 11.0. We are trying to use wireless printers to print labels. The printers are configured as remote BSD printers. The ping times for these printers are higher than those for wired printers. The first ping is about 400ms, with following pings about 8 ms. Wired printers usually are 1-2 ms. The problem is that small jobs (<500 bytes) print fine, but larger jobs
(~750 bytes) hang for a couple of minutes before printing. Does anyone have any ideas about how I can prevent the hanging behavior?

[Steven E. Protter]

Those jobs are hanging because its taking longer than it would through a wire to feed the job into the print buffer.

If you change the configuration to lower the ping times, the jobs will print faster.

Wireless is 10 to 100 times slower than a 100BaseT wired connection.

Translation: its a feature.

SEP

[Dave Chamberlin]

Steve - I dont think it is a pure speed issue. They can print the 500 byte labels all day without a glitch, the 700 byte labels hang for several minutes. Perhaps there is a buffer threshhold that the larger labels are above? Is there ANYTHING I can tweak to improve the larger size transmission?

[Chris Vail]

To isolate this problem, you need to print some of these labels from something other than the N4000. Do you have the same delay when printing them from your M$ systems? I lean toward the idea that this delay is due to the fact that it is wireless more than anything else.


Chris

[Steven E. Protter]

It may not be a speed issue.

It could be a short term interference issue.

It could be a network configuration traffic issue.

When a job is hanging, try and ping the printer. If you get no reply look into the issues above.

SEP

[Jeff Schussele]

Hi Dave,

I suspect packet size may have an affect here.
What happens when you ping with larger & larger size packets?
In 11.0 default packet is 64 - smallest 8 & largest 4095.
I suspect there's a router or switch along the way who's MTU setting is causing a problem & probably causing massive retrans.

Rgds,
Jeff

[A. Clay Stephenson]

Both 500 and 750 byte print jobs are tiny print jobs. The UNIX box doesn't have a clue (and doesn't care) that it is printing to a wireless device. The longer ping times shouldn't matter as well as those values are in the expected range for WAN connected printers and they work just fine.

My best guess is that the printer is waiting for an end of job character and failing to see one, it finally times out and dumps the output. I would ask the developers how they terminate a "small" label vs. a "large" label. Add a FF and see if the problem goers away -- or what ever character sequence is appropriate for your label printer.

[doug mielke]

we've had problems with some wireless Access Points wanting to re route large messages to other APs. This feature can be disabled on our wireless equip.
Scenario is:
Big message starts at the 2 or 11 meg rate, fills buffers of targets,
Wireless AP sending message sees that the route is blocked or busy and tries to find another route through another AP..

Now we have a retransmitt / re-assembly challenge. Does LP or the jetdirect handle this well? If not, printing loarge jobs could be a pain.

[Jeff Schussele]

I think Clay's on to something here.
I'd suggest you set up a print-to-file ptr for these label jobs & examine the output of both type jobs.
A time-out condition could certainly account for the symptom.

Rgds,
Jeff

[Dave Chamberlin]

Thanks for all the suggestions! We tried pinging with larger ping sizes and they work ok - though the first has a LONG return time. We also checked that the print jobs do have the EOF they need. We have found since then that there is some dependency on how fast the operator is scanning items to print the labels. It does not seem to hang as much if he goes a little slower. Thanks again.