In the basic configuration (without the survivability features), an IPDA installation function depends completely on the availability and reliability of the LAN/WAN infrastructure used. The failure of an access point's IP connection leads to failure of the access point.

Total failure of the IP infrastructure leads to the failure of all access points. Only the central system and the "classic" peripheral units connected continue to work.

Survivability for signaling and payload ensures that OpenScape 4000 also offers the greatest availability in distributed operation. The public telephone network/an alternative LAN connection (in the case of Signaling Survivability) can be used as an alternative route in the event of an IP network failure or if the IP network temporarily fails to provide the requisite quality for voice transmission.

If the IP connection from an access point/OpenScape 4000 SoftGate to the central system fails, there can be no interaction between the access point/OpenScape 4000 SoftGate and the central system. Messages from the terminal devices and trunks in the access point/OpenScape 4000 SoftGate are temporarily buffered on the (v)HG 3575, while messages from the central system are buffered in the central processor. If the duration of the failure exceeds a definable limit, the Access Point/OpenScape 4000 SoftGate is reset, thereby disconnecting all calls.