"Steven M. Bellovin" <smb@research.att.com> wrote:
> >... dhclient isn't doing that if it can not reach the DHCP server?
> 
> Utterly certain -- I set the lease time to two weeks...

  In low signal conditions, you're probably losing association with
the AP.  i.e. The link layer goes down.  This is functionally similar
to pulling a wireless card out of the PCMCIA slot on your laptop.

  If you're using wireless authentication methods (EAP-TLS, TTLS,
etc), then after losing association, you can't get back onto the
network until you re-associate and re-authenticate.

  If you're not using wireless authentication, then you still have to
re-associate, and you'll get your network back once that happens.

  I'm not sure how possible/useful it would be to mark the loss of
association as a "temporary" network failure.  There's always a chance
that when you re-associate, you'll get a new IP.

  Alan DeKok.