18.1.7.2. Native SIP trunking 
If an OpenScape 4000 system fulfills all requirements for SPE (see Chapter 3, “Configuration”), the gateway will try to set up a secure SIP
connection to the partner gateway if this is configured in the SIP trunk profile (see
SIP
Connectivity > Section
3.3, “SIP Trunk Profiles”).
For native SIP trunks only SDES as payload encryption mode is supported, if payload
encryption
is released for the trunk partner. The payload encryption mode cannot be configured.
If an OpenScape 4000 system fulfills all requirements for SPE (see Chapter 3, “Configuration”) and if security is released for the activated SIP
trunk partner, then the gateway will try to set up a secure connection to the partner
gateway.
INFO:
Starting with Software Version V11R0, it is possible to run native SIP trunks with
SPE
enabled without the need to activate SPE on the full OpenScape 4000 system (ZAND and
SIPCO).
For this, SPE needs to be enabled via AMO TDCSU and the corresponding security configuration
needs to be done via the WBM.