kern/48617: After about 1 hour of inactivity WiFi network connection is lost (rum0 interface still active)

[zbigniew2011%mail.com@localhost]

>Number:         48617
>Category:       kern
>Synopsis:       After about 1 hour of inactivity WiFi network connection is 
>lost (rum0 interface still active)
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Feb 25 22:30:00 +0000 2014
>Originator:     Zbigniew
>Release:        6.1.3
>Organization:
>Environment:
NetBSD Trurl 6.1.3 NetBSD 6.1.3 (MYKERNEL) #0: Sat Feb  8 16:18:14 CET 2014  
root@Trurl:/usr/src/sys/arch/i386/compile/MYKERNEL i386
>Description:
When connected to network via WiFi (in my case: using Linksys WUSB54GC-EU 
"dongle"), I noticed, that when the machine is left idle for about 1 hour, it 
is enough to lose connection to network. The interface is still in "active" 
state, it still has its IP address assigned by DHCP server - but there is no 
network connection anymore.
Tried it several times - both on shipped GENERIC kernel, and now also with my 
own.
>How-To-Repeat:
Easy: use Linksys USG dongle, connect to network, leave machine idle about 1 
hour. After this time the network connection seem to be terminated.
>Fix:
There's a workaround: it's possible to keep network connection by keeping some 
little activity - for example: in any of terminals one can leave "ping -i 60 
www.some.site.com". Such humble activity seems to be enough to maintain 
connection.