TCP = Transmission Control Protocol IP = Internet Protocol
IP provides an unreliable connectionless communications protocol that is in wide use on the internet. TCP sits on top of IP and provides reliablility and connections. TCP/IP sits between the application level protocols (such as HTTP) and lower layer stuff (network cards etc)
Java provides the java.net package of classes which provide a number of general purpose network related classes. Some of these (in particular the Socket classes) relate to TCP/IP. These classes will need to be implemented under JOS to get TCP/IP networking going.
This topic is currently under heavy brainstorm on the firstname.lastname@example.org list. If you would like to partecipate please read the archives at http://cjos.sourceforge.net/redist/mail/arch/ and subscribe at http://jos.org/mailman/listinfo/arch
RanieriArgentini used to be working on an implementation called JEPS (JOS Experimental Protocol Stack).