The current API changes for iOS9 state that -setKeepAliveTimeout:handler:
is deprecated.
Up to now, this was the only way that a VoIP SIP app on iOS could maintain its registration with the SIP-server.
This technique is used by various apps like LinPhone and others.
Does anybody have a view on the proposed alternatives by Apple ? Or will SIP be crippled starting from (post-)iOS9 ?
Apple document the alternative in the page you linked: