[ih] Fw: TCP adoption in 1984

Sun May 3 10:29:28 PDT 2026

 Maybe the original question was about how many were 1822 to IMPs vs. Ethernet in 1984? At Stanford, we had something like two using 1822 in the CS department (KL-10 known as SU-AI and DecSystem-20 SCORE) plus another couple in the medical center, where Bill Yeager was doing his own multi-protocol router. We ran TCP over Ethernet on probably a couple dozen Sun workstations, using the V-System, and BSD on several more Vax machines. MIT and CMU had similar environments, with only a couple machines using 1822 and the majority by then using TCP. The legacy networks were PUP at Xerox PARC and Stanford, ChaosNet at MIT, and at least at Stanford they faded away with new growth in TCP. The 3 megabit Ethernet (actually something like 2.97 to align with USA cable TV standards) was only used for Altos, the laser printer, and a batch of Unibus boards made by Xerox for PDP-11s and Vaxes.
PUP (and I think ChaosNet?) did not require ARP, but ARP was implemented and deployed by the time the RFC was published; it is very simple. The use of repeaters and flooding bridges was only short-lived since their disadvantages were so obvious.
Now as for any non-"research", any customer of Sun Microsystems (and the company network itself, the largest customer!) had their own TCP/IP network. However, most of these (such as Sun's) did not route IP packets to the wider Internet. There were a series of what would now be called firewall hosts, starting with Tom Lyon's SunLink product. So we had exactly one that could route to the outside Internet, and a thousand or so that routed only internally. An interesting historical question to me was: what year were the majority of TCP/IP hosts in the world not directly routable on the main research Internet? My guess would be soon after, in the mid eighties at least.
Bill
    On Sunday, May 3, 2026 at 09:59:14 AM PDT, vinton cerf via Internet-history <internet-history at elists.isoc.org> wrote:  

 from gemini:

The first internet gateway (router), developed by Ginny Strazisar at BBN in
1976/1977, was a *PDP-11/40* that used the *BBN 1822* interface on both
sides.
The Packet Radio Side

Just like the ARPANET connection, the Packet Radio Network (PRNET) side
used a *bit-serial (Distant Host) BBN 1822 interface*.

The Packet Radio Units (PRUs), manufactured by *Collins Radio* (Rockwell),
were specifically designed to emulate an ARPANET IMP's host interface. This
allowed existing hardware and drivers to be repurposed with minimal
physical modification.
Key Technical Details

  -

  *Physical Hardware:* In the PDP-11/40 gateway, the connection was
  typically handled by *ACC (Advanced Computer Communications)* interface
  cards, specifically the *ACC LH-DH/11* (Local Host-Distant Host) UNIBUS
  controller.
  -

  *The Interface Logic:* Even though the physical layer was the same 1822
  bit-serial interface used for the ARPANET, the *logical protocol* was
  different. Instead of the standard Host-to-IMP protocol (used to talk to
  ARPANET IMPs), the gateway used the *Channel Access Protocol (CAP)* to
  communicate with the PRU.
  -

  *Speed:* The 1822 interface on the PRNET side supported the radio
  network's data rates, which were either *100 kbps* or *400 kbps*
  depending on the specific PRU model and configuration.

Why use 1822 for both?

The use of the 1822 interface for the PRNET was a strategic choice by
DARPA. Since the ARPANET already had a well-defined, reliable
host-to-network interface, the developers of the PRU simply adopted the
same physical and electrical standards. This ensured that the BBN-developed
gateway software could use similar low-level drivers to talk to both a
fixed landline network (ARPANET) and a mobile radio-based network (PRNET).

Was there a particular reason you were looking into the hardware layer of
the PRNET gateway—are you researching the early development of TCP/IP or
the hardware of the PDP-11?

On Sun, May 3, 2026 at 12:47 PM Barbara Denny via Internet-history <
internet-history at elists.isoc.org> wrote:

>  Forgot to reply to the list.
>    ----- Forwarded Message ----- From: Barbara Denny <b_a_denny at yahoo.com>To:
> Vint Cerf <vint at google.com>Sent: Sunday, May 3, 2026 at 09:45:36 AM
> PDTSubject: Re: [ih] TCP adoption in 1984
>  I think for the 1976 demo the gateway was still  in the packet radio
> station and only supported ARPAnet and PRnet. I think PRUs (Packet Radio
> Units) originally had an 1822 interface. By the time of the LPR I think the
> interface was HDLC but that change might have happened earlier.
> I think the 1977 demo used a separate box for the gateway and may have
> been ported to MOS by then. The packet radio station used ELF for the
> operating system.
> I am waiting to hear if the MIT gateway had an ethernet interface.  Quite
> some time ago on this mailing list, Noel mentioned he found my request for
> a gateway. I am begining to wonder if that is why i asked for one.  I
> think i had to specify exactly what interfaces i wanted.
> barbara
>    On Sunday, May 3, 2026 at 07:40:52 AM PDT, Vint Cerf via
> Internet-history <internet-history at elists.isoc.org> wrote:
>
>  I don't think it needed ethernet - it was connecting PRNET to Arpanet and
> SATNET and likely used BBN 1822 interfaces on the IMP sides. Less clear to
> me what the interface looked like on the packet radio side - maybe a bit
> serial link?
>
> v
>
>
> On Sun, May 3, 2026 at 9:25 AM Carsten Bormann via Internet-history <
> internet-history at elists.isoc.org> wrote:
>
> > On 2026-05-03, at 14:35, Craig Partridge via Internet-history <
> > internet-history at elists.isoc.org> wrote:
> > >
> > > I don't recall if it supported Ethernet or simply connected two
> > > ARPANET-technology networks (of which there were a few at the time).
> >
> > https://www.internethalloffame.org/inductee/virginia-travers/
> >
> > …talks about “radio and satellite”.
> > 1976/1977!
> >
> > Grüße, Carsten
> >
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