What is PDU & connections

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The TCP packets between the ESME and the SMSC are called PDU's (Protocol Data Units). The following types of PDU's are used in SMPP connections:

1-     Session Management PDU

•       Connection, disconnection and keep alive

•       bind, unbind, enquire_link

2-     Message Submission PDU

•       Submitting messages to a mobile phone

•       submit_sm

3-     Message Delivery PDU

•       Delivery of messages to the SMPP client

•       deliver_sm