Any Chance to keep an call going if the current internet connection of the SBC is lost and routed to other DSL-Line (with different external IP)

[Timo83]

Hi everybody,

I've one customer suffering from quite bad internet connection. Bad in this context means the line drops 3-10 times a week and is re-synced afterwards (Downtime 1-2 Minutes). At this moment I'm pretty sure I know every technician in my area. Nobody was able to find and solve the problem. So as it seems impossible to kill the root cause I was thinking about workarounds to live with it in best possible way. To make it more stable we simply ordered a second line and the firewall is handling any lost connections by routing them over to the second line.

For normal HTTP based traffic I use a load sharing algorithm, for anything more keen on the sender IP they are sticked to one line with a failover to the second. The PBX is located in the cloud the connection is carried out via one SBC at the moment.

While this setups overall increases the up-time of at least one internet connection dramatically (the second line has same problems by the way, but at least I get know to new service technicians) It can not help with suddenly dropped calls.

Are there any fancy things or tricks I could do with this setup to avoid a call from being dropped if the active line breakes down. It would be okay if I got a second or so no voice stream but then the other line kicks in and the session is held. Is this somehow possible? In the end the SBC uses TCP packes that can be rerouted, or not?

Any ideas or thoughts are welcome

Best regards

Timo

 

[YiannisH_3CX]

Hi @Timo83

Your scenario looks really bad with 2 internet connections both dropping multiple times a week. Is this an area thing or is it only happening with this specific customer?

Unfortunately I don't know of a way to keep an active call going if the internet drops in the middle of a call. Even if the SBC fails over to the second internet line it has to establish a new connection to the PBX with a different contact and port so all ongoing calls will be lost.

 

[Timo83]

Yes it's a nightmare. Especially if from customers side of view you are responsible.

As far as I know it is a little bit of both. The DSLAM seems to be totally full. New lines are only assigned with 50Mbit even if 100 should be possible. In two years Fiber to the home should be finished - so on the one hand this will help a lot on the other nobody will invest in VDSL any more.

Other companies around are bigger and using SDSL lines so they have no problems. But this is not an option because of long build and contract times as well as too high prices (compared to the fiber prices in 2 years when its ready)

So the goal is it to keep it running as good as possible until we can switch to a fiber connection. Therefore I'm reaching out to all sides. SD-WAN, MLPPP and who knows maybe some fancy firewall tricks somebody knows

In a normal network I would simply assign a cluster IP and switch this to the active interface. One ARP Package later the switch is updating the path and everything is up and running with only a few lost packages - all this techniques must be present on ISP side as well I'm pretty sure everything is redundant there. Maybe I'm just using the wrong trigger words or I'm to small

 

[Timo83]

While writing the reply I got a fancy idea....
Lets assume I'll book an AWS Instance and start the SBC there.
It should have a stable connection to the internet for sure as well as a public IP. For access of the local devices I could use site-to-side vpn - I guess I can also use two or three over each DSL Line and use them as an automated backup. Or can somehow route them to seperate nics on the instance and simply bond them together on both sides. luckily this is then normal networking stuff) The result should be a stable vpn tunnel to my local side with a SBC sitting on top and waiting for connections from the PBX. The access can be secured down to only allow request from the PBX and on PORT 5090 - will this be safe enougth? It it okay to present a SBC "open" to the internet? Can this work?

 

[YiannisH_3CX]

What you are proposing is technically possible but in that case why an SBC in the first place? Let me just add that we have not tested this scenario so I cannot confirm it will work without issues but the endpoints and the PBX should not be aware of any change so you might be fine.

You are essentially talking about something like VRRP although I just know the terminology and have not done something like this before.

If you do get it working however I would love to hear your feedback and have a look at your network diagram.

 

[cobaltit]

So for your scenario, a SDWAN device should work. It operates very similarly to your VPN scenario, but it is purpose built for this application. It's basically a commercial version of your solution. All traffic would ride over the VPN to the datacenter and then go to the internet from there.