This Recommendation specifies the signalling architecture for Internet protocol (IP) based short message service (SMS) over next generation network (NGN)@ and identifies the signalling requirements for the interworking between NGN and mobile networks supporting SMS. The IP-based short message over NGN is encapsulated in accordance with the SMS layer defined in [ETSI TS 124 011]. With regard to SMS over mobile networks@ this Recommendation conforms to [ETSI TS 123 040] and [TIA-637] which specifies the technical implementation of SMS in circuit switch (CS) domain of GSM/UMTS networks and cdma2000 network.