How disappointing that no-one contributed to this bug. There are many
pleas for help from people with similar printing problems... and none of
them are very conclusive.

I ran a wireshark trace of the LPD protocol exchange between cups and my
network printer. The trace was big, but the later stages showed a tcp
protocol violation from the host. A quick search turned up only one hit.
It also occurs with IPP, but could apply to ANY tcp protocol!

http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=478062

This is a linux kernel bug handling tcp timeout recovery. It applies to
ALL kernels after 2.6.22, which explains why I also get the problem on
feisty. The bug also applies to 2.6.25, so presumably will affect
releases newer than hardy.

I am sure MANY people are suffering from this problem but don't know
where to look for a solution. Here is the suggested bypass...

1. Power-off your printer to totally clear the corrupt job.
2. Clear the printer spool queue.
3. Power-on the printer
4. sudo sysctl -n net.ipv4.tcp_frto and confirm the current value is 2.
5. sudo sysctl -w net.ipv4.tcp_frto=0 (turns the buggy logic off completely)

Note: this bypass will not survive system reboots.

After that, the printer works just fine with my 2.6.24-19-generic kernel
on an old and slow pentium 3 600mHz processor.

BUT the bypass doesn't work at all with the 2.6.24-19-rt kernel on my
pentium 4 3gHz processor.

I then tried the alternative bypass (net.ipv4.tcp_frto=1), but print
jobs hung on both systems.

I guess the only way to get this problem resolved properly is to join in
on the kernel debugging effort....

-- 
No print output after upgrade to hardy
https://bugs.launchpad.net/bugs/225603
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