Enterprise Services for Cross-System Data Exchange 
You can use either PI-based enterprise services or PI-independent enterprise services for asynchronous communication between SAP Supplier Relationship Management (SAP SRM), SAP ERP, and other systems.
PI-based enterprise services require the installation of an SAP NetWeaver Process Integration (SAP NetWeaver PI) server and are used in the following business scenarios:
Service Procurement Classic
Service Procurement External Staffing
Strategic Sourcing
Operational Contract Management
Plan-Driven Procurement with Supplier Integration
For more information, see SAP Help Portal at .
PI-independent (asynchronous) enterprise services are based on the Web Service Reliable Messaging (WSRM) protocol. They do not require the installation of an SAP NetWeaver Process Integration (SAP NetWeaver PI) server and are used in the following business scenarios:
Service Procurement Classic
Operational Contract Management
Note
The following restriction applies: supplier self-services (SUS) still requires the installation of SAP NetWeaver PI.
For more information, see PI-Independent Enterprise Services.