If you have high security requirements, you can use Secure Network Communications (SNC) to protect RFC connections in the Transport Management System. This encrypts the RFC connections that are generated during the TMS configuration.
For more information about SNC, see Secure Network Communications (SNC).
If you use SNC for RFC connections between SAP systems, you must ensure that the Transport Workflow cannot trigger any imports into these systems.
The SAP Systems in your domain are set so that they can use SNC-secured RFC connections to communicate with each other (as described in the SNC documentation). You do not need to convert the whole system landscape at once. Instead, you can choose to do it system by system.
Remember that you must only prevent unsecured RFC access to systems once all systems in the domain have been converted to SNC. Take into account the restrictions on TMS mentioned above when you activate the SNC-secured connections for your SAP Systems.
The RFC connections between the systems in your transport domain are protected by SNC. If you use a domain link to communicate with systems in another domain, this connection is also protected by SNC.