Verizon EVDO Issues

Thu Apr 9 15:12:57 UTC 2009

"Steven M. Bellovin" <smb at cs.columbia.edu> writes:

> On Thu, 09 Apr 2009 07:15:44 -0400
> "Robert E. Seastrom" <rs at seastrom.com> wrote:
>
>> 
>> Seth Mattinen <sethm at rollernet.us> writes:
>> 
>> > I have a few Sprint EVDO cards. They go into standby when nothing is
>> > actively going on and fire up within seconds when there is
>> > something to do. I regularly use everything from SSH to streaming
>> > video without any issues. I only notice the delay with SSH when I
>> > don't type anything for a few minutes and it has to come active
>> > again, but I can leave it idle for hours and it never drops.
>> 
>> Interesting.  When I got my Sprint EVDO card (u727) a year and a half
>> ago, they were pretty nasty about gunning down (bidirectional spoofed
>> RST coming out of the middle of the network somewhere) any TCP
>> sessions that were idle for ten minutes or more.  Quite repeatable and
>> verified on the downlow by People With Insight that this was in fact
>> expected behavior from boxes that were in the middle of the network
>> due to "politics" (unlike Verizon, Sprint appears to put no
>> restrictions on inbound connections to the evdo-host).  Putting this:
>> 
>> ServerAliveInterval 60
>> 
>> in ~/.ssh/config was an effective work-around.  I have not revisited
>> the issue to see if Sprint has corrected this behavior.  Perhaps
>> budget constraints or customer complaints have caused Sprint to
>> revisit the necessity of having extraneous hardware in their network.
>
> 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'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