https://www.cisco.com/c/en/us/td/docs/wireless/asr_5000/21-19_6-13/Ultra-IoT-CSGN-Admin-Guide/21-19-ultra-iot-csgn-admin/21-17-Ultra-IoT-CSGN-Admin_chapter_01110.html
Ultra IoT C-SGN Administration Guide, StarOS Release 21.19 - S11U Interface Support on S-GW for...
S11U Interface Support on S-GW for CIoT Devices