You are actually running both. TCP/IP is a transport protocol; NetIPC
is an application programming interface. The EDA/SQL install you did
can use either the NetIPC API or the "Berkeley Sockets" API, which HP
for some reason calls ARPA Services. Both NetIPC and ARPA API's can run
over the TCP/IP transport.
These concepts are clearly explained in any good textbook which
describes the ISO 7 layers of networking. If you are going to be
venturing into client/server software it pays to understand these
concepts as you evaluate products.