Howto:SIP redundancy / failover

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Overview

We often encounter scenarios in which the reliability of the SIP connection is to be ensured. There are several approaches and scenarios how to achieve this SIP redundancy or failover.

How well SIP redundancy and/or failover works, depends on the interaction between the PBX and the carrier providing the SIP account.

PBX / Gateway

To support various carriers, innovaphone has already implemented the following configurable features:

  • Accepting trunk registrations from multiples Sources (GWs)
  • Always place the call on a primary trunk and in case of an error, on a secondary trunk or round robin
  • Receive calls from multiple trunk registrations
  • Route calls between GWs back and forth
  • Rerouting of failed calls

Carrier scenarios

Of course your possibilities here depend on the carrier's feature-set

If you don't know if your provider(s) do support redundancy, you can check our test reports of the Certified SIP Providers in our wiki or ask you provider.


Two permanent active SIP Interfaces

The best practice would be if the Carrier accepts two registrations from different sources with the same credentials

  • SIP Interfaces on two Gateways with identical configuration
    • Both Interfaces register to the Trunk Object in the PBX
  • The routing configuration on the Gateway should be identical
  • The call distribution is not critical, but needs to be considered in the configuration
    • Some carriers send all incoming calls on the primary trunk only and expect all outgoing calls over the same primary trunk
      • Outgoing Calls must be first sent to the primary Interface, then to the secondary one
    • Some carriers use both trunks for incoming and outgoing calls

Active SIP Interface, secondary disabled SIP Interface

If the Carrier doesn't accept two registrations from different sources with the same credentials then you can prepare the failover scenario, but you have to switch here manually.

  • SIP Interfaces on two Gateways with identical configuration
    • The primary Interface should be enabled
    • The secondary Interface should be disabled
    • Both Interfaces register to the Trunk Object in the PBX
  • Routing on the Gateway should be identical
  • The call distribution is straight-forward because there is only one single active Interface at the same time
  • If the primary trunk fails, it must be disabled manually and the secondary one activated


- There are some ideas to achieve this with the help of some lines of codes and your monitoring appliance which would trigger and be able to disable/enable these Interfaces via HTTP(S) commands.

- There are some ideas to achieve this with the help of V13 App Platform and the SDK by developing your own App to automate this process suiting your needs

- Today we have no automatic mechanism for SIP Interfaces which enable a SIP interface if the other one fails, but there is a feature request where you can vote for it.