The protocol (TCP/IP or SPX) used for a particular TSA connection depends upon the entries present in UnixWare /etc/unixtsa.conf file, the protocol(s) bound to the network interface card on the NetWare server, and (for TCP/IP connections) the SYS:ETC\HOSTS file on NetWare.
When you invoke a backup engine, it looks on the network for advertised connections to TSAs running on other systems. You can choose from the available TSA connections that the server has detected on the network.