Prior to SBC 8.2, the SBC supported ingress precondition interworking when the ingress side of the call supported precondition attributes, but when the egress side of the call did not.
The SBC is enhanced to send the initial INVITE to the egress when it meets the ingress side preconditions.
The SBC sends the P-Early Media (PEM) header as sendrecv
to ingress when it satisfies the following conditions:
performPrecondtionRenegotiation
flag is in enabled state on the ingress trunk group% set addressContext default zone <zone_name> sipTrunkGroup <siptrunkgroup_ingress_name> signaling performPrecondtionRenegotiation <enabled | disabled>
% set addressContext default zone ZONE_INGRESS sipTrunkGroup TG_INGRESS signaling performPrecondtionRenegotiation enabled