In this section:
The SBC Core provides a preconditions support feature to reserve network resources as a preventative measure to minimize chances of session failure due to lack of resources before alerting the called party. This prevents a "ghost ring" where the called party is alerted before the call is set up. The SBC Core supports preconditions interworking functionality only when one leg of a call supports preconditions and other does not. The SBC supports preconditions functionality on either of the legs (egress or ingress). With this feature, preconditions interworking is decided based on the precondition profile configuration, present in the Common IP Attributes of the IP Signaling Profile (IPSP). This feature supports ISUP-SIP and SIP-SIP preconditions interworking, and provides transparency by dropping/adding of preconditions attributes between supporting or non-supporting peers. The preconditions are configured from the SBC at the SIP Trunk Group level using the parameters “preconditions” (for incoming requests) and “transmitPreconditions” (for outgoing requests). The SBC Core completes the ingress preconditions when the call terminates at the PSX script. Users can configure the list of script names (in the Note The configurable script name is the same as the script name that PSX returns. The The SBC adds a P-Charging-Vector header with the Note The psxScriptProfile
) for which the SBC performs ingress preconditions interworking. The ingress preconditions trigger when one of the configured script names matches with the PSX returned script name. The script execution continues after the ingress preconditions are met.
The SBC allows a maximum of three script names to be configured.pemInterworking
flag inhibits sending the P-Early Media header in the first 18x response for the ingress preconditions interworking scenario.termIOI
parameter to the 18x response sent to the ingress network. The termIOI
parameter sends the terminating networking identifier to the ingress network. The SBC creates and sends the termIOI
parameter when there is no egress network, which occurs when the call is terminated in the script. When there is an egress network, the termIOI
parameter is received from the egress network.termIOI
parameter is configured in the Signaling SIP Trunk Group.
NOTE: During an ingress precondition interworking scenario, if the remote precondition is met in PRACK, the SBC processes it and sends the INVITE towards the egress.
For in-depth details of SBC preconditions interworking and preconditions profile flags interactions, refer to Reserving Network Resources.
% set profiles signaling ipSignalingProfile <profile name> commonIpAttributes preconditions State <disable | enable> StrengthMandatoryPolicy <disable | enable> StrengthMandatoryPriority <1-100> StrengthOptionalPolicy <disable | enable> StrengthOptionalPriority <1-100> SupportIfEgressIPTG <disable | enable> UPDATEPreconditionsPolicy <disable | enable> UPDATEPreconditionsPriority <1-100>