SIP Redundancy

[ETAU]

What do people use for SIP redundancy? (Small office - 1-10 users, small budget)

Scenario:
1. Analogue line used for fax machine. Also provides ADSL service. QoS configure on modem, works well.

Issue: What if ADSL goes down for whatever reason, or the SIP provider has an outage?

What would be the most cost effective backup to allow calls to be sent or received?

The options I can think of are:
1. Additional analogue line with gateway - Will allow single concurrent call. Not a big help as it is only one concurrent call.
2. Have a second SIP provider on basic plan that is only used if SIP provider #1 of down and out. Would also need second internet connection to be fully redundant. Is 3G/4G/LTE suffcient/reliable as a backup for a fixed line ADSL connect? Will there be NAT/IP Address issues?

 

[Saqqara]

We use the following,

1. Dual internet connections, with different suppliers - this is OK, unless they is a physical issue with the outside telecom wiring.

2. Backup PSTN line (normally the same line used for ADSL, Infinity), I know it is only one line but better than nothing. Our sip provider can transfer the call to the PSTN line in the event of a failure of the sip connection.

 

[ETAU]

We use the following,

1. Dual internet connections, with different suppliers - this is OK, unless they is a physical issue with the outside telecom wiring.

2. Backup PSTN line (normally the same line used for ADSL, Infinity), I know it is only one line but better than nothing. Our sip provider can transfer the call to the PSTN line in the event of a failure of the sip connection.

What gateway do you use for the analog line to 3cx?
You have two wired ADSL connections with two separate providers, have you had any issues with a line physically being down or a problem back at the exchange affecting both providers?

 

[lneblett]

I guess it depends on your business tolerance for an outage and their budget to avert. In most cases, the SIP providers are able to forward calls to another number to include mobiles. This, while allowing only one call, will still bring the mobile's voice mail into play and perhaps call waiting as well.

If the SIP provider has an outage, then chances are that they are down completely and there is nothing you can do, so pick a provider that itself has disaster recovery and the ability to forward.

If the internet goes down, then you still have the mobile, but having a redundant connection here usually implies having an analog gateway with analog lines. This is where the budget comes into play. If you are lucky enough to have more than one internet delivery service available, you could also consider this route, but then IP addresses will change and you will need to consider how to handle with your network.

Most of the smaller sites I have simply forward to a cell. They went SIP for the cost advantage as well as being able to have a PBX with all the bells and whistles that their larger brethren have. The internet in my area is more prone to issues than the SIP provider.

 

[Saqqara]

What gateway do you use for the analog line to 3cx?

We use Linksys SPA-3102, which I understand are no longer available (end of life product), so I am not sure what we will be using next.

 

[leejor]

If you do some searches, you can still find a 3102. I would recommend using that, or any other single line gateway, if there is another make available, connected to the PSTN line used for Faxing, alarm systems, etc. In an ideal situation, you'd have access to a line that you could easily accept incoming calls. If the line is used for "other services" normally, you'd want 3CX to ignore incoming calls during "normal" operation.

An analogue line is a good idea to have as the emergency number (911, 999,112) secondary route.

 

[ETAU]

I guess it depends on your business tolerance for an outage and their budget to avert. In most cases, the SIP providers are able to forward calls to another number to include mobiles. This, while allowing only one call, will still bring the mobile's voice mail into play and perhaps call waiting as well.

If the SIP provider has an outage, then chances are that they are down completely and there is nothing you can do, so pick a provider that itself has disaster recovery and the ability to forward.

If the internet goes down, then you still have the mobile, but having a redundant connection here usually implies having an analog gateway with analog lines. This is where the budget comes into play. If you are lucky enough to have more than one internet delivery service available, you could also consider this route, but then IP addresses will change and you will need to consider how to handle with your network.

Most of the smaller sites I have simply forward to a cell. They went SIP for the cost advantage as well as being able to have a PBX with all the bells and whistles that their larger brethren have. The internet in my area is more prone to issues than the SIP provider.

Thanks, this is very helpful. I think you sum it up well. I will put forward the mobile option as the cheapest fallback for the two sites (1 bussiness) that I am currently working on.