SMPP PDU and working

SMPP is used by clients to connect to an SMSC (Short Message Service Center). Entity which connects to SMSC using SMPP is known as ESME. SMSC can also send information back to ESME (ex: delivery report of previously send message).

So the connection can be done in 3 ways.


Transmitter : ESME only send data to the SMSC
Receiver : ESME only receives data from the SMSC
Transceiver : ESME can send and receive data to and from the SMSC.

SMPP Protocol is level-7 TCP/IP protocol . Communication between SMSC and ESME is done using TCP/IP Packets known as PDU (Protocol Data Unit) .

Available PDU Types are

Session Management PDU’s
Connecting, disconnection and connection keep alive.

Message Submission PDU’s
Submitting messages to a mobile phone.

Message Delivery PDU’s
Delivery of messages to the SMPP client.

Ancillary Operations PDU’s
Message query, cancel and replacement.



The following SMPP PDU's are used the most:
bind_transmitter / bind_receiver / bind_transceiver


Used to connect the client with the SMSC



submit_sm


Used to submit a single message from the client to the SMSC ( MT ). This packet contains the sender and recipient address, message body and some optional parameters.

deliver_sm


When a messages has to be delivered to the client this packet is used ( MO ). It contains information about the sender of the message and the message body. This PDU is also used to send delivery reports to the ESME.

query_sm

To query the state of a previously sent message, this command is used. You need a message reference to query a message. Most provider require you to use delivery reports instead of querying the messages all the time.

enquire_link


This packet is sent once in every x minutes to check if the connection is still alive. If not, the connection is terminated. This packet is also used to keep dial-up connections alive ( for instance ISDN ). The most used timeout for SMPP connections is one minute.

unbind

Some other PDU's are data_sm,alert_notification,submit_multi,cancel_sm,replace_sm etc


SMPP optional parameters

To extend the SMPP protocol with extra parameters, TLV parameters, also called optional parameters were introduced in the SMPP protocol since version 3.4


More information on PDU is avaibale from SMSFORUM.NET
Download SMPP 3.4 documentation