rt message relay layer (SM-RL) ensures reliable transmission of SMS messages between, firstly, the mobile, and, secondly: - the interworking mobile services switching center (SMS-IWMSC) for outgoing SMS messages (Figures 10.1 and 10.2); - the gateway mobile-services switching center (SMS-GMSC) for incoming SMS messages (Figures 10.1 and 10.2); The short message control layer (SM-CL) ensures reliable transmission of SMS messages between the mobile and the MSC server entity (Figure 10.1). VoLTE and ViLTE: Voice and Conversational Video Services over the 4G Mobile Network, First Edition. André Perez. C ISTE Ltd 2016. Published by ISTE Ltd and John Wiley & Sons, Inc. 274 VoLTE and ViLTE For the architecture of SMS over SGsAP, the mobility management entity (MME) ensures relaying SM-CL messages and the MSC server entity that SM-RL messages (Figure 10.1). For the architecture of SMS over SIP, the IP short message gateway (IP- SM-GW) provides relaying SM-RL messages (Figure 10.1 and 10.2). Mobile SMS-SC SM-AL SMS-IWMSC SM-AL SMS-GMSC SM-TL SM-TL MSC Server SM-RL SM-RL Not defined SM-CL SM-CL SGsAP Figure 10.1. Protocol architecture for SMS over SGsAP Mobile SMS-SC SM-AL SMS-IWMSC SM-AL SMS-GMSC SM-TL SM-TL IP-SM-GW SM-RL SM-RL Not defined Figure 10.2. Protocol architecture for SMS over SIP 10.1.1. SM-TL layer SMS-SUBMIT message carries outgoing SMS messages from the mobile to the SMS-SC entity. SMS-SUBMIT-REPORT message is an acknowledgment on the part of the SMS-SC entity, positive or negative, of the SMS-SUBMIT message. SMS-DELIVER message carries incoming SMS messages from the SMS-SC entity to the mobile. SMS-DELIVER-REPORT message is an acknowledgment on the part of the mobile, positive or negative, of the SMS-DELIVER message or the SMS-STATUS-REPORT message. Short Message Service SMS-STATUS-REPORT is a report sent by the SMS-SC entity to the mobile which transmits the SMS-SUBMIT message, report relating to the delivery of the SMS message to the destination. 10.1.2. SM-RL layer The header of the SM-RL layer contains