What is SMPP then?
The service you use to send sms. Traccar probably has a smpp client built in.
Companies like Clickatell, Twillio
SMPP is a protocol and it's not based on either HTTP or REST. REST on the other hand is NOT a protocol. It's a way of organizing API on top of the HTTP protocol. Overall the question makes very little sense.
Well then you need to hive an example of a provider who can be used
I have solved it and now have a working solution using smsglobal.com
My smpp provider say they only support http and rest protocol. Which protocol do traccar use?