13.1.2. What is Used as an Alternative Route for Signaling? 
If the IP link of an access point/OpenScape 4000 SoftGate fails, an
alternative route in a network is required that is not affected by the
failure.
The basic demand on the network for the alternative route is simple:
- It must be independent of the IP network whose fault is to be bypassed via the alternative route.
- A connection device for the access point/OpenScape 4000 SoftGate is required, which acts as a modem. It must be actively callable and provide the access point/OpenScape 4000 SoftGate with “Ring Indication“.
- The central system must be supported by a corresponding router on an STMI2/4 with WAML function.
There are two different ways for signaling survivability: