samba/ ksmbd would probably be the closest equivalents; sftpd is always an alternative, somewhat easier to set up, but slower and (on the client side) often less integrated into commercial operating systems.
Perhaps I'm not conveying this idea clearly enough - I have a Mac and I want to use Time Machine built in the OS to do backups to an eSATA-connected disk on my router.
Would SAMBA be the preferred network protocol or Netatalk?