>>41
TCP/IP are just some stacked protocols, you can setup a human powered TCP/IP server, which reacts on paper notes, if you want. It would not be very efficient, but who cares. We have such a certain in the real world. It is called the postal services. Although you get something which is more close to UDP/IP for TCP/IP you have to pay more.
Message passing is a abstraction, which includes TCP and IP.
>>40
No, I actually mean only to maintain all the services of a node in the network. If a program needs to call a services, it can ask the network which node provides it.
They should not share state, otherwise it is not feasible to do. That is the price you pay for easy parallelism.