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Author Topic: Combined DSL and 4G/5G  (Read 656 times)

Weaver

  • Addicted Kitizen
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  • Retd sw dev; A&A; 4 ◊ 7km ADSL2; IPv6; Firebrick
Combined DSL and 4G/5G
« on: February 20, 2020, 03:12:36 PM »

Some kitizens have urged me to go to 4G. This isnít practical on its own for many reasons. Iíve though about this quite a lot over recent years. If I were to do it I would need to combine it with DSL to get the reliability. This would require L2TP on 4G. That would mean reduced MTU unless thereís a 4G link type that has say 1600 byte MTU, like BT[?], to make it suitable for tunnels. My 3G/4G NICs have a really low MTU already rather than a higher MTU. So if there is such a high MTU 4G service then Iím not seeing it or I need to get rid of my problem hardware first.

Realistically I would be looking at a really low MTU all the time.

Another problem with combining 4G + DSL would be the huge 4G RTT; not only that but the big differences in 4G RTT and ADSL2 RTT when bonded together might confuse TCP because itís seeing a constant variation in timing.

What do you think?
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aesmith

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Re: Combined DSL and 4G/5G
« Reply #1 on: February 21, 2020, 06:36:39 PM »

I'm not convinced that reduced MTU would be a deal breaker.  We have lots of customers who run their corporate networks over encrypted tunnels, either because that's over the Internet or because they don't trust their carrier.  Occasionally we need to configure MSS over-ride if they have applications that don't properly adapt.
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Weaver

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  • Posts: 8682
  • Retd sw dev; A&A; 4 ◊ 7km ADSL2; IPv6; Firebrick
Re: Combined DSL and 4G/5G
« Reply #2 on: February 21, 2020, 08:20:47 PM »

Agreed. Iím more worried about the weird RTT. And the horrible performance of 4G here.
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Alex Atkin UK

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Re: Combined DSL and 4G/5G
« Reply #3 on: February 22, 2020, 12:59:37 AM »

What stopped me load balancing with 4G was the sudden and unexpected latency increases.  It would trigger pfSense to mark the gateway as down and the instant traffic stopped flowing the latency went back to normal and it was marked up again, so the firewall would be restarting constantly killing all connectivity. :(

I tried increasing the latency at which it marks the gateway as down but that didn't help as when 4G was having the latency issue it was barely usable so needed to be marked as down.  It was at that point I ordered the second VDSL line.

I honestly don't know how anyone copes with using 4G as their primary connection.  I guess they just get used to the fact some days it will lag.

I believe 5G is supposed to fix this with TDMA?  This is also the key feature that should fix WiFi, eventually.
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Exchange: INTAKE (ECI DSLAM) Router: pfSense (i5-7200U) ISP/Modems: Zen (Home Hub 5A running OpenWrt) + Plusnet (VMG-3925-B10B) WiFi: Ubiquiti nanoHD