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Author Topic: What technology should I use for a failover?  (Read 1779 times)

boozy

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What technology should I use for a failover?
« on: May 22, 2019, 01:35:19 PM »

I’m at a bit of a loss at what to try next.
I need a pretty much constant connection to my house (in order that something can be monitored).  Due to problems with rain I have two circuits to my house one running at 40/10 and the other at 60/10, with the first deliberately restricted.
The rain problem (significant noise when the rain starts) has been much improved over winter where it tended to take down only one line, but now it’s taking down both lines every time the rain is
heavy. I’ve tried the obvious approach of just letting the speed reduce when this happens, the sync speed is low due to the noise on the line, but that’s had the unintended consequence of the 40/10 line being on retx high and the 60/10 line being on retx low…. And it made little difference to the stability, presumably as bitswap can’t act fast enough or the noise isn’t at its highest by the time a resync has taken place.

The frequency of the problem isn’t high enough for me to class it as a fault but it is pointless having both lines active as I’m gaining nothing from the second line. It’s also causing a few issues for my edgerouter which doesn’t seem to like both of the load balance group falling over at the same time.

Anyone know a good candidate for the second connection.



On an extra note I did write something to maintain the QoS at home and it allows you to see up to 5 modems together, I’ll bung it up when I get the chance. I was trying to figure out how to monitor noise(by predicting snr from the qln and HLog) and some more data would be useful. It’ll take most time listing the problems I’m aware of :D – although I’m behind the Project Manager’s schedule for a new patio area so I may have to perform manual labour first.
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aesmith

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Re: What technology should I use for a failover?
« Reply #1 on: May 22, 2019, 01:57:50 PM »

Depending on the frequency of use, and quantity of data to be passed, 4G would be an obvious option to consider.   However if what happens is your main line goes slow or flakey, you need to think about how to trigger fail over and fail back.  Most conventional mechanisms expect the line to be down as a trigger, either for example by polling a test destination or by looking at PPP login status.

On 4G the Smarty tariff may make sense, as they credit unused data from the following month's bill, making it only £5/month if you didn't use any.

On the other hand surely an FTTC connection shouldn't drop just because it's raining, can the fault really not be found?
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gt94sss2

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Re: What technology should I use for a failover?
« Reply #2 on: May 22, 2019, 02:48:29 PM »

The frequency of the problem isn’t high enough for me to class it as a fault but it is pointless having both lines active as I’m gaining nothing from the second line.

I would report the dropping connection in poor weather as a fault - especially as its happening on both lines - and see if Openreach can identify/fix it. If their is audible 'noise' on the line during a voice call during poor weather, report it/them as an landline fault instead of a broadband one.
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boozy

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Re: What technology should I use for a failover?
« Reply #3 on: May 22, 2019, 03:35:25 PM »

OR have visited quite a few times now, with the only improvement being when the second line was installed. The problem (probably) is external to the lines, so I’m struggling to see what they could do except wait for rain :).  To be fair to them, it was happening during the slightest drizzle and lasting a few hours causing 4 or 5 resyncs on a wet day - now it mostly only happens in heavy rain and lasts 5 minutes at most.   The edgerouter will pick up loss of sync (or I can write something to spot it) and do the failover.  Change of IP I’m already dealing with, so that adds no extra complication.
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Weaver

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Re: What technology should I use for a failover?
« Reply #4 on: May 22, 2019, 09:30:57 PM »

I use AA’s data SIM service for 3G backup. Their service does 4G and I do have 4G coverage but I don’t have the right USB NIC for 4G. The service costs £2.40 per month plus a fortune for data up/down, but it’s ideal as it never gets used.

You get as many routable static IPv4 addresses as you want, a single static IPv4 by default. No IPv6 at the moment, been waiting and asking for this for years, but there is an IPv6-in-IPv4 proto 41 tunnel service which I use and which does work and this gets round the problem.

I have no change of source IP. I don’t use the 3G NIC’s IP address really, everything gets re-routed by AA at their end, and during failover all stuff is sent to the 3G NIC by them still destined to my existing IP ranges, so even up/downloads that are in progress at the time of failover just carry on uninterrupted. With a change of source IP all the L4 connections (eg TCP) have to get dropped of course.
« Last Edit: May 22, 2019, 09:45:56 PM by Weaver »
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boozy

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Re: What technology should I use for a failover?
« Reply #5 on: May 22, 2019, 10:10:36 PM »

It's the AAISP line that will be getting the chop, so that sounds a reasonable way of going about it (especially if I can maintain the IP for external access).  Fixed IP is a necessity.  £20 per Gb should still leave it cheaper than the fixed line (Three were £100 per Gb last time I broke their limits - unsurprisingly I don't deal with them anymore).

I'll have a chat with them when I next work from home.
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Weaver

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Re: What technology should I use for a failover?
« Reply #6 on: May 22, 2019, 11:16:26 PM »

You will be able to keep the IP address(es). Mine are associated with the account eg weaver@a in clueless and you just associate them with the 4G link by ticking a tick box in clueless to say which lines the addresses are to route to and in what state - there are rows of tick boxes where I might describe each row as state=1=main, or state=2=fallback or whatever and the tick boxes are one per line * per state.

In clueless you can set up address ranges and move them around.
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