Prior to Mavericks, when you turned on File Sharing on a Mac workstation (in the Sharing system preference pane), the Mac was only shared out via the AFP protocol. If you wanted to share out via the SMB protocol, you could click on the Options button.

This behavior has been changed with Mavericks. Now when you turn on File Sharing it uses both the SMB and AFP protocols. Computers connecting that don’t specify a protocol will get SMB by default. SMB and/or AFP can be disabled by clicking the Options button.