Integrating SAP using IS and TN servers


I have experience with webMethods Enterprise server, but have little knowledge about Integration Server. Now I have an assignment with integration with SAP and Trading partner using Integration Server with Trading Networks and SAP IS Adapter. I need to prepare a document on this with process flow with all the necessary services involved.

The business follows

Scenario 1: Partner to SAP.
Scenario 2: SAP to Partner.

Can anyone tell me how the partner and SAP and vice versa communicate each other in step by step?

Thanks in Advance