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 (5.3.2.20), destination_port (5.3.2.21), more_messages_to_send (5.3.2.34), sar_msg_ref_num (5.3.2.22), sar_total_segments (5.3.2.23), sar_segment_seqnum (5.3.2.24) are not processed and are not supported.

The parameter TLV message_payload (5.3.2.32) is also not processed.

References:

http://www.3gpp.org/DynaReport/23040.htm

https://en.wikipedia.org/wiki/Concatenated_SMS

Important Note:

The Gateway will automatically send failed delivery receipts if not all message parts are received within 30 minutes.