nanog mailing list archives

Re: Cellular backup connections


From: Dovid Bender <dovid () telecurve com>
Date: Fri, 28 Dec 2018 07:29:08 -0500

It's strange. When we use T-Mo on an andriod device the ping times are
30-40 ms. When we try with the modem + raritn console box it jumps to min
of 100+ ms (the modem is high up on top of the rack and we test with the
phones we are on the floor) - Can 5 feet higher make it that much worse?


On Fri, Dec 28, 2018 at 7:23 AM Brandon Martin <lists.nanog () monmotha net>
wrote:

On 12/28/18 7:06 AM, Dovid Bender wrote:
Hi All,

I finally got around to setting up a cellular backup device in our new
POP. I am currently testing with T-Mobile where the cell signal strength
is at 80%. The connection is 4G. When SSH'ing in remotely the connection
seems rather slow. Ping times seem to be all over the place (for
instance now I am seeing: rtt min/avg/max/mdev =
174.142/336.792/555.574/99.599 ms) . Is that just cellular or is that
more related to the provider and the location where I am? I could in
theory test with VZ and ATT as well. With Verizon they charge $500.00
just to get a public IP and I want to avoid that if possible.

Thanks and sorry in advance if this is off topic.

LTE with a good connection on a lightly loaded cell should be
significantly less than that in both absolute terms as well as jitter.

I used LTE (Sprint) for a couple years as my primary connectivity when I
moved out into an area with zero connectivity (fixing that now).  I
typically saw ~30-40ms to Chicago, which is the nearest major carrier
PoP.  Jitter was typically less than 10ms.  VoIP was usable.  Others in
the area on other carriers have reported similar.

Sprint gave me a public IP with no up front charges but did charge $5/mo
for it.

As you're probably aware, the "signal strength" ("bars") indicators that
are presented to the consumer-facing interfaces are often very cooked.
Depending on which RSSI you're looking at, a "very good" signal is
probably in the realm of -70dBm to -110dBm (note that there are two RSSI
metrics commonly used with LTE, and they tend to differ by ~20dB).

--
Brandon Martin


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