On Fri, 08 Dec 2006 14:26:46 +0100
Joerg Sonnenberger <joerg@britannica.bec.de> wrote:

> On Fri, Dec 08, 2006 at 08:13:03AM -0500, Steven M. Bellovin wrote:
> > I have a similar need.  In particular, I have an EVDO wireless card
> > which is less happy -- i.e., it often drops the call -- if it sees
> > an outbound packet with an invalid source address.  
> 
> Source address as in MAC address or source address as in IP address?
> 
Source IP address.

EVDO is a CDMA cellular technology.  My card shows up as ucom0; I set
up a PPP connection to the provider's network.  (My understanding is
that PPP is actually terminated by the card, which then speaks
something else over the wireless link, but that's not really relevant
here.)  Sometimes, the connection will drop, especially if I use the
card from a moving train (which is, in fact, how I'm sending this note;
I'm on my way from New Jersey to Washington, DC).  When that happens, I
have to redial and I get a different source address.  (The other end
gets *very* unhappy if I configure pppd to ask for my old IP address.)




		--Steve Bellovin, http://www.cs.columbia.edu/~smb