Estimated LTE Data Utilization in Failover Scenario

Shaun_Dombrosky · July 30, 2019, 4:05pm

Good Morning,

First time NANOG poster, apologies if I breach etiquette.

Does anyone have any first-hand data on how much data a small-medium business (SMB) can expect to consume in a failover scenario over a 4G/LTE connection? Retail, under 50 head count, using PoS, maybe cloud accounting software, general internet activity, 8 hour time period. Wonder if anyone is using a Cradlepoint or SD-WAN solution that could pull a few quick numbers from a dashboard for me. I haven’t had much luck in my searches.

Appreciate any info anyone can provide.

Thanks,

Shaun Dombrosky
Data Network Engineer

E: sdombrosky@blackfoot.com

www.blackfoot.com

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Matt_Harris · July 31, 2019, 2:46pm

Hey Shaun,
I’d recommend pulling that data from the device normally facing their internet connection. Does it support netflow or even just basic snmp statistics that you could graph? Ostensibly the traffic level would be the same regardless of whether using an LTE backup connection or the primary internet connection unless you somehow prohibited certain traffic when on LTE. Ultimately though, your best bet is going to be to get real stats over the course of a couple of weeks and then you’ll understand better the traffic patterns based on time of day, day of the week, etc, as well, as this is likely relevant.

Good luck!

Blake_Hudson · July 31, 2019, 4:03pm

100% agree with Matt. Something also to keep in mind is the SMB’s peak data rates. The primary (I assume ethernet) uplink may have a sub 10ms latency and 100Mbps or greater data rate while the LTE connection is probably several times slower in terms of bandwidth and latency. If designing a failover connection, customer expectations may need to be managed: internet access may be up, but will be noticeably degraded when on LTE. A backup cable connection may be better for VoIP or other latency/jitter sensitive applications and of course anything that relies on a static IP (server, vpn, etc) will probably break if the primary connection is down. Would be a good idea to test the failover connection during a few different time periods to gauge employee experience.

–Blake

Shawn_Ritchie · July 31, 2019, 4:37pm

Yep. We sell solutions, both Cradlepoint and SD-WAN-based, and a big part of it is going over with the customer “you can’t just fail over all your regular traffic; pick biz-critical functions and deny everything else or you’re going to a) be very unhappy with speeds/performance and b) be EVEN MORE unhappy with the overage bill”.

Get some data over a regular work week or so of their traffic, preferably with some flow data so you know what kinds of traffic/apps are consuming the bandwidth. Have the customer ID which of those flows would be critical if the primary connectivity died; size the cell plan appropriately or, if that can’t be done due to data caps, make sure needed tunnels for backoffice-type stuff will even work over your particular solution, etc… help them figure out what else can be dropped in an emergency.

Other thing to consider is that almost all US cell plans have a pretty small data cap, even “unlimited”, and our testing shows that just backend Cradlepoint or SD-WAN chatter can add up to a GB or 2 a billing cycle; need to make sure your configs explicitly block any cellular usage unless the primary connection has gone completely down.

Paul_Amaral · July 31, 2019, 4:54pm

In my experience with LTE is that its never enough. We have bank branches
with 20Mbs metro lines and on rare occasion when that circuit drops 4G LTE
will provide you with 10mbs at best also note that latency is much higher
which can mess with ipsec/VOIP etc. I dont think you can pick how much
bandwidth you will get with 4G LTE. From the testing I have done with VZ 4G
I get 10mbs down and 2/3 up with a -65 RSSI. Its still better to have LTE
for a backup then not to have it.

I have used cradlepoint and now switched to cisco ISR 1111. I find the
crandlepoint to be not as reliable as the cisco ISR. The cradlepoint will
get extremely hot, go down for no reason and has poor signal compared to the
ISR 1111 with LTE. I would stay away from the cradlepoint and find a Cisco
LTE solution.

Again like I said a backup of any kind even if not sufficient in bandwidth
is better than nothing.

Paul

Sabri_Berisha · July 31, 2019, 11:01pm

Hi,

From the testing I have done with VZ 4G
I get 10mbs down and 2/3 up with a -65 RSSI. It’s still better to have LTE
for a backup then not to have it.

You will have to keep in mind that if there is a generic service outage in your area, you will not be the only one going LTE/4G for backup purposes. That means you will kind of have to lower your expectations in a real world scenario...

Again like I said a backup of any kind even if not sufficient in bandwidth
is better than nothing.

That I totally agree with.

Thanks,

Sabri

Kenny_Taylor · August 1, 2019, 2:22pm

We did some testing with VZ and Sprint earlier this year. Sprint provided rates around 20-25 mbit down and 2-3 mbit up *if* it was an area with decent coverage and the connection was on band 41. Much lower rates on band 25/26. We noticed that their regular unlimited hotspot plans perform well up until the 50 GB mark. The evening after we'd hit the 50 GB mark, throttling kicked in and pinned the connection down to about 128 kbit, regardless of cellular network congestion. VZ seems to throttle the connections after hitting the 25 GB mark, but it's gradual and appears to be more deprioritization than shaping.

We tried VZ in a couple of rural areas and quickly discovered that there wasn't enough bandwidth to those particular towers. We could pull 20 mbit down regularly around 6:00 am, then by lunch time we'd get less than 1 mbt down. We deployed an ISR router with LTE NIM and a linux box running iperf hourly to do that testing. Don't base your rate estimate on afterhours testing, and I'd echo the other comments that the cellular network will get slammed during an outage/disaster scenario and will undershoot your estimates.

Worth noting, I can pull 45-60 mbit on my T-Mobile phone all day long. Does anyone have experience using T-Mobile plans for LTE backup?

Kenny

Paul_Amaral · August 1, 2019, 6:05pm

To clarify, the test was done around 1PM and was simple speed test, probably
could have gotten more throughput at the end of the day but these are used
as backups and if the primary connection goes down, I dont have the luxury
to pick when that happens. I mainly used these as backups and I make sure
the customer knows that this is a temporary solution, the speed/latency will
not be as good as the primary connection. If the customer understands this,
then 4G LTE is a great solution especially for a backup. It's also great for
getting branches up ASAP while waiting for fiber etc. I haven't tried
T-mobile LTE but that seems really high.

Paul