Talk:Network Control Program

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Contents 1 Misinterpreted (?) BSDTalk info 2 Missing Information 3 NCP location 4 Layer locations

[edit] Misinterpreted (?) BSDTalk info

If you look at the NCP as described in the Protocol Handbook, it is obvious that it runs on the same host as the rest of the protocol stack. And, incidentally, I saw many examples of that (including Unix implementations). While it is true that NCP (and the whole ARPANET) was limited to 256 hosts originally, it was expanded in the late 70s to 4,096 hosts (ref: BBN 1822). So I'm deleting that whole weird sentence based on the BSDTalk interview. As a practical matter, TCP/IP incorporates bits of both NCP and the BBN 1822 protocol, and the latter did indeed reside on a special purpose box (the IMP). That must be the source of the confusion. Rick Smith 23:55, 18 April 2006 (UTC)

[edit] Missing Information

This article says nothing about the use of NCP by IBM. See my comments at Talk:systems Network ArchitectureRdmoore6 20:13, 18 January 2006 (UTC)

[edit] NCP location

I tried to make clear that ARPANET NCP executed on a host rather than a "specialized processor". RFC36 seems to make the host residence of NCP clear. I inserted the link to RFC36 in further reading.

Perusal of the first thirty Google hits on "Network Control Protocol" suggested that it iss not often confused with the RFC36 context of NCP and so I deleted that sentence. The link to the BSDTalk Interview doesn't seem to work quite right but I have left it for now.Rdmoore6 05:43, 17 March 2006 (UTC)

[edit] Layer locations

The text as I found it was very confusing; it was talking about the lower layers (physical, data link) being implemented on the IMP, versus the host, and I think that's wrong. The IMP-host interface, as spec'd in 1822, included all three (physical, data-link, and network), and the host had to implement all three in/on the host to be able to communicate with an IMP. I suspect that what the author was trying to say was that the IMP-IMP protocols were different from the host-IMP protocols, so I have modified the text to say that directly.

Also, when I wrote "usually connected to the IMP using another kind of interface, with different physical, data link and network layer specifications", that's because of the rare VDH (Very Distant Host) interfaces. Local Host and Distant Host (LH and DH) used custom bit-serial interfaces with interlocked signalling (with the "there's-your-bit", "ready-for-next-bit" lines), and were essentially identical (except that LH was a TTL interface, whereas DH used differential pair). Nothing about a host-IMP interface using LH or DH looked anything like an IMP-IMP connection. VDH was totally different; it looked a lot more like the IMP-IMP protocol. VDH operated over a modem, and so VDH hosts could be a long way from their IMP (hundreds of miles in some cases, IIRC). The protocol between the modem interface on the host and that on the IMP was identical to the IMP-IMP protocol for that application. I.e. the VDH host-IMP connection shared the physical, and some of the data link, protocol specifications of the IMP-IMP interface.

But none of this is about NCPs, so this is really the wrong place for this anyway... Noel (talk) 23:50, 11 August 2007 (UTC)