SMPP clients may send long messages by segmenting messages (at the ESME level) and sending each and every segment to the Gateway; every segment should have the correct User Data Header (UDH) value.
The Gateway expects every segment to have the paremeter esm_class (5.2.12) bit field 6 to be set; indicating that the short_message (5.2.22) value contains a UDH.
Please consult the 3GPP TS 23.040 standard for details of the User Data Header structure and concatenated SMS messages.
TLVs related to concatenation / UDH such as source_port (18.104.22.168), destination_port (22.214.171.124), more_messages_to_send (126.96.36.199), sar_msg_ref_num (188.8.131.52), sar_total_segments (184.108.40.206), sar_segment_seqnum (220.127.116.11) are not processed and are not supported.
The parameter TLV message_payload (18.104.22.168) is also not processed.
The Gateway will automatically send failed delivery receipts if not all message parts are received within 30 minutes.