The ARPANET is often mentioned as the Internet's precursor. But what protocols did it run with if not TCP/IP?

2 Answers 2



NCP was used in ARPANET before TCP/IP

It was fully replaced with TCP/IP in 1983, replacement started in 1981, https://www.rfc-editor.org/rfc/rfc801

  • That's what I was looking for
    – Holy Sheet
    Sep 28, 2012 at 8:11

One of the greatest treasures produced by DARPA is probably the collection of early RFCs IENs and other public documents that record the development of the Internet. Try getting equivalent free documentation for ISO OSI or for proprietary technologies like Netware IPX/SPX. In part this is one important reason why Internet Protocols prevailed over the competition. The early RFCs were mostly concise, clear and easy to read and understand (this isn't so much true of later RFCs).

See RFC1

   Information is transmitted from HOST to HOST in bundles called
   messages.  A message is any stream of not more than 8080 bits,
   together with its header.  The header is 16 bits and contains the
   following information:

           Destination     5 bits
           Link            8 bits
           Trace           1 bit
           Spare           2 bits
  • The protocol went through many changes since RFC 1. One would need to read at least the first 1k RFCs (up until the NCP→TCP migration) to see how it looked at the end.
    – user1686
    Sep 27, 2012 at 22:19
  • 3
    @grawity: Yes, the IENs are also interesting. For example IEN2 "We are screwing up in our design of internet protocols by violating the principle of layering. Specifically we are trying to use TCP to do two things: serve as a host level end to end protocol, and to serve as an internet packaging and routing protocol. These two things should be provided in a layered and modular way. I suggest that a new distinct internetwork protocol is needed" Sep 27, 2012 at 22:23
  • Thanks for that answer. I've looked into the early RFCs but could not identify a name for the protocols described therein (other than IMP software).
    – Holy Sheet
    Sep 28, 2012 at 8:10

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