Samba is an implementation of Server Message Block. SMB 2 (introduced in Vista) reduces the number of SMB commands from over 100 to 19.
Samba makes use of the SMB File System
ReactOS uses Samba-TNG as its basis for Samba (due to Samba-TNG having separate services).
The key differences between the two programs are in the implementation of the NT Domains suite of protocols and MSRPC services. Samba makes all the NT Domains services available from a single place, whereas Samba TNG has separated each service into its own program.
ReactOS has started using Samba TNG services for its SMB implementation. The developers of both projects were interested in seeing the Samba TNG design used to help get ReactOS talking to Windows networks. They have been working together to adapt the network code and build system. The multi-layered and modular approach made it easy to port each service to ReactOS.
Using Samba in ReactOS