[113250] in North American Network Operators' Group
Re: Verizon EVDO Issues
daemon@ATHENA.MIT.EDU (Robert E. Seastrom)
Thu Apr 9 11:15:03 2009
To: "Steven M. Bellovin" <smb@cs.columbia.edu>
From: "Robert E. Seastrom" <rs@seastrom.com>
Date: Thu, 09 Apr 2009 11:12:57 -0400
In-Reply-To: <20090409105557.7ef6b75c@cs.columbia.edu> (Steven M. Bellovin's
message of "Thu, 9 Apr 2009 10:55:57 -0400")
Cc: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
"Steven M. Bellovin" <smb@cs.columbia.edu> writes:
> On Thu, 09 Apr 2009 07:15:44 -0400
> "Robert E. Seastrom" <rs@seastrom.com> wrote:
>
>>
>> Seth Mattinen <sethm@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
