[Cake] [Bloat] Fwd: [Galene] Dave on bufferbloat and jitter at 8pm CET Tuesday 23

Nils Andreas Svee me at lochnair.net
Fri Feb 26 09:25:25 EST 2021

On 2/26/21 8:26 AM, Taraldsen Erik wrote:
> *Fra:* Nils Andreas Svee <me at lochnair.net>
>     I am indeed running them on Ethernet. I don't actually use the
>     B818 for anything else than as a LTE modem, so I wouldn't know, if
>     I could get the thing to bridge I would. Or replace it with
>     something else entirely that I can control, but that doesn't seem
>     to be an option on FWA. That said the Zyxel looks like a better
>     option since I assume it acts like a bridge by default.
> The Zyxel device indeed acts as a bridge, or at least as close 
> approximation as we can get it.  The PDP addressing protocol in mobile 
> networks requres the address termination to happen where the SIM card 
> resides.  So the device does some trickery with brctl, routing and 
> iptables to simulate a bridge setup.
Oh nice. Sure it's not a "true" bridge, but for all intents and purposes 
it gets the job done. Kinda tempting to get one of those now, if only to 
avoid the whole using DMZ mode on the B818 to pass everything through.
>     I dumped the raw signal stats the web interface grabs in an XML
>     file together with the Flent tests. Also did some upload only
>     tests tonight at different speeds (no VPN in play this time).
> rsrp is good and rsrq is great at your location.  However you have 
> ended up on the 800MHz band.  That is intended for coverage, not 
> capacity.  It uses only 10MHz bandwitdh and is shared with a lot more 
> customers.  You probably should be able to get an 1800MHz frequency 
> which has 20MHz and is shared among fewer customers.
Yeah I thought it should be pretty good. I don't really know how to 
interpret those numbers, but Teltonika's guidelines seemed to indicate 
that it should be good.

Good point about the bands. For the first months after we signed up it 
tended to switch between 800Mhz and 1800Mhz and mostly stay on 1800Mhz, 
but now it's been stuck on 800Mhz for quite some time.

I wanted to try and lock it to 1800Mhz, but there's no option for that 
exposed in the GUI that I can find.

>     Most likely yes. That's been my observation as well, that it
>     generally acts up the worst when somethings using the upstream.
>     Not entirely sure what I can do about that, seeing as I had to
>     shape at 5Mbit to get rid of the worst spikes (but not all). 
> This is tricky.  You don't have a static set of resources.  You 
> request resources "as needed".  The "as needed" amongst other things 
> reads the buffer back pressure.  So if you shape to far down the LTE 
> device will not request enough resources.  Shape to high and there 
> will not be enough resources available to share.  And available 
> resources vary with number of subscribers on that cell, weather, the 
> subscribers usage and interference from other cell towers.  To get a 
> proper solution to this I don't see a way around getting the chipset 
> manufacturers on board.
Downside of shared mediums of course. So basically my best bet is to 
find somewhere in the middle to shape on, or use the pping stuff to 
somehow dynamically configure it. Of course, but we don't really have a 
voice with them, so the best we can do is support your efforts however 
we can.
>     On that point, I would've liked to collect signal stats over time,
>     but the B818 seems to insist on chucking me out after being idle
>     for a few minutes, better known as scraping the stats with cURL
> Have you tried to use the telnet service port (20249) on the B818?  
> Not all variants have that open but you could give it a shot.  You 
> also may need to acquire an datalock code for the "at^datalock=" command.
> telnet LAN_IP 20249
I had not, I didn't scan higher ports. It *is* open though, so I was 
able to connect to it. It only yells at me if I try to run any of the 
few AT commands I know (except /at)/, not sure if that's because of the 
datalock code. If that's what I'm missing, how does one go about getting 
a hold of one of those? When I looked it up I only found some sites I 
have concern about the legitimacy of.
> This is getting LTE/5G spesific.  Not sure if it belongs on the list.  
> Let us know if we are generating noise.
> -Erik
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