Verizon EVDO Issues

Steven M. Bellovin smb at cs.columbia.edu
Thu Apr 9 11:28:35 CDT 2009


On Thu, 09 Apr 2009 11:12:57 -0400
"Robert E. Seastrom" <rs at seastrom.com> wrote:

> > I use a Verizon Wireless u727; before that, I used a PCMCIA card.
> > I've never had problems with drops on idle.  *However* -- if there
> > was a packet from the wrong IP address, the older card would drop
> > the connection -- apparently, that behavior was required by the
> > spec.  (I haven't checked if the newer one will do that.)  So, if
> > the EVDO connection dropped while I had, say, an IMAP or ssh
> > session open, and I dialed back in, the next TCP packet would cause
> > EVDO to drop again...  I finally "fixed" it by creating ipfilter
> > rules in my ppp-up script to block all "bad" packets from going out.
> 
> Interesting.  I never had that behavior exhibited on my old PCMCIA
> card on Verizon or on my u727 on Sprint.  What OS platform were
> you on lappie-wise?

I run NetBSD but I know that the problem also showed up on Linux -- a
friend who worked for an equipment vendor also saw it, and he checked
the actual EVDO specs.

We suspect the problem doesn't show up for Windows users because
Windows appears to terminate all connections with extreme prejudice
when the link goes away, so there won't be any TCP transmissions to
induce the failure.
> 
> I've thought on a couple of occasions that a "geek bake-off" between
> EVDO and 3G providers looking for technical jack moves on the
> providers' part would make for a nice NANOG lightning talk.  Sadly, I
> haven't the time to devote to such an endeavor.
> 
> -r
> 
> 
> 



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




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