History of Initial Internetting Concepts
The original ARPANET grew into the Internet. The Internet was based on the idea that there would be several independent networks of quite arbitrary design, which began with ARPANET as the groundbreaking package switching network, but soon to include package satellite networks, base packet radio networks, and other networks. The internet that we now know it is an important underlying technical idea, namely open architecture network.
In this approach, the choice of any single network technology was not dictated by a particular network architecture, but could be freely chosen by a vendor and made to interact with the other networks through a meta-level “Internetworking Architecture“. Until that time, there was only one general method of connecting networks. This was the traditional circuit switching method where networks were to connect together at the circuit level and pass individual bits on a synchronous basis along with a portion of an end-to-end circuit between a pair of end positions.
Remember that Kleinrock had shown in 1961 that parcel exchange was a more efficient change method. Along with package switching, specific interconnection arrangements between networks were another option. While there were other limited ways to connect different networks, they required one to be used as a component of the other, rather than acting as a peer of the other in providing the end-to-end service.
However, the NCP did not have the ability to address networks (and machines) further downstream than a destination IMP on the ARPANET, and a change in the NCP would therefore also be required. (The assumption was that ARPANET was not changeable in this regard). NCP was on ARPANET to provide end-to-end reliability. If any packets are lost, the protocol (and possibly any programs it supports) will come to grinding. In this model, the NCP had no end-of-line check, as the ARPANET would be the only network that existed, and it would be so reliable that no host error was needed.
Kahn, therefore, decided to develop a new version of the protocol that could meet the needs of an open architecture network environment. This protocol will eventually be called the Transmission Control Protocol / Internet Protocol (TCP / IP). While the NCP used to act as a device driver, the new protocol would be more like a communication protocol.