[ih] Fwd: Early internetworking ca. 1976 / First ARPANET Link Put Into Service

[Greg Skinner]

Forwarded for Barbara

> ----- Forwarded Message -----
> From: Barbara Denny <b_a_denny at yahoo.com>
> To: internet-history <internet-history at elists.isoc.org>
> Sent: Wednesday, February 4, 2026 at 09:34:45 PM PST
> Subject: Re: [ih] Early internetworking ca. 1976 / First ARPANET Link Put Into Service
> 
> Having trouble with the mailing list again so not all the text for this thread is included.
> 
> This discussion covers a time period before I worked on packet radio. John Shoch's recollection made me curious about when TCP was first used over packet radio and when the first generation radios (EPRs?) were available. The place I have started to look for this information is the TIU (Terminal Interface Unit).  The TIU had TCP and TELNET. It also had SPP (station-packet-radio protocol) to improve reliability and support for other functions. FYI,  I think the early packet radios had an 1822 interface.
> 
> I haven't found definitive answers to my questions but I did find a a webpage that has some links to documentation in case you are interested in the TIU.
> 
> https://gunkies.org/wiki/Terminal_Interface_Unit
> 
> BTW,  the use of DSP on this web page does not mean Digital Signal Processing. It refers to the Dispatch/SPP modules.
> 
> 
> barbara
> 
> 
> On Tuesday, February 3, 2026 at 12:23:55 PM PST, John Shoch via Internet-history <internet-history at elists.isoc.org> wrote:
> 
> 
> Towards the end of last year there was a thread here on the first Arpanet
> link at SRI, and Barbara Denny was kind enough to share a note (11/3/25)
> from Don Nielsen also reminding us of the earliest multi-network tests of
> the TCP Internet at SRI:
> // 3. First 2-net demo of TCP was on 27 Aug 1976.? PRNET and ARPANET.
> // 4. First 3-net demo of TCP was on 22 Nov 1977.? PRNET, SATNET, and
> ARPANET.
> 
> As I recall, prior to that time all of the TCP design, implementation and
> testing had been done just on the Arpanet.  Building on the early work at
> Stanford, the effort grew to include people at SRI, BBN, and elsewhere.
> Those demonstrations in 1976 and 1977 -- with a gateway and multiple
> networks -- were  tremendously important milestones along the path to what
> became the Internet as we know it today.
> 
> In response to that post, though, I was asked about the actual state of the
> Xerox PUP internetworking effort at that time, in mid-1976.  It took me a
> while to do an archeological dig -- I wanted to find the original documents
> to ensure that we got the history right.  I found a couple of interesting
> things and wrote up a summary.  My friends at the Computer History Museum
> have long encouraged us to document some of the work, and it was suggested
> "you should share it before we lose this history."
> 
> So, some of the notes, documents, and insights on internetworking in 1976
> (as seen from a slightly different perspective):
> 
> --In 1972, about 4 years earlier, the first INWG meeting had taken place at
> the ICCC meeting in Washington DC.
> --In the summer of 1973, about 3 years earlier, there were ongoing meetings
> at Stanford, and Cerf and Kahn were drafting the TCP paper at the Cabana
> hotel in Palo Alto.  That same summer there were early discussions at PARC
> about the proposed Ethernet (as well as an alternative design simply called
> LOCAL network), and the need to interconnect them.  A memo from Aug. 1973
> reported a discussion on "...the problems of interfacing the LOCAL and
> ETHER networks.  This memo describes a rather general proposal for
> introduction of a message format standard which emerged from the
> discussion.  The adoption of the standard would enable us to interconnect
> different networks—essentially forming a network of networks…..”  A drawing
> includes ARPA, ETHER, and LOCAL networks.
> --In the Spring of 1974 the Ethernet was maturing (while the alternative
> LOCAL net never emerged), and there were some basic Ethernet-specific
> protocols implemented (EEFTP).  Yet it was clear that there would be a need
> to interconnect Ethernet networks, both locally and across geographies.
> Metcalfe had been participating in some of the INWG meetings, but it was
> also evident that we could not wait for that effort -- we needed something
> immediately.
> --That led to Bob's initial draft memo, "A Proposed PUP -- PARC Universal
> Packet" dated March 19, 1974, which began:
> "This memo is written and should be read with caution; its purpose is to
> promote a standard.  Because there isn’t an ice cube's chance in hell that
> our (or anyone else's) standard will be adopted without interminable debate
> and revision, the memo itself is quick and dirty. This way we get the ball
> rolling early. ...  A list of the packet networks at Parc would include, in
> arbitrary order of pedigree, (1) Ethernets, (2) Localnets, (3) Arpanets,
> (4) MCAnets, and (5) EIAnets.”
> [MCANets connected Data General Novas.  "EIAnets" evolved into a backbone
> packet switching network among Gateways, made up of leased serial lines.]
> .
> --Over the next two years the further design, implementation, and
> refinement of PUP were done primarily by David Boggs and Ed Taft.  Progress
> was reported in a series of memos, initially by Metcalfe and later by Boggs
> and Taft:
>   PUP Revisited
>   PUP Converging
>   Naming and Addressing Conventions for PUP
>   A Nova Gateway
>   Implementation of PUP in Tenex
>   PUP Again
>   PUP Connection State Diagram
>   PUP Servers on Maxc
>   etc., etc., etc.
> 
> --So where did things stand, after two years of work, in mid-1976?  The
> best document I have found describing things ca. 1976 is from 6 months
> earlier, a "draft" of "PUP Overview" by Taft dated Dec. 21, 1975.  He
> reports:
> "Local communication is carried on by means of several independent Ethernets
> (passive broadcast networks operating at 3 mb/s) and two MCAs
> (Multiprocessor
> Communications Adaptors for interconnecting Nova computers, operating at
> 1.6 mb/s).
> Long-haul communication is carried on over the Arpanet (a store-and-forward
> packet
> switched network·operating at 50 kb/s). We are considering making use of
> other
> transport mechanisms, such as optical fibers for very high bandwidth local
> communication, leased phone lines for regional communication at modest
> bandwidths,
> and commercial·packet switching services such as Telenet."
> The memo goes on at length to describe Basic Principles, Levels of
> Protocol, Standard Packet Format, Inter-Network Addressing, Fragmentation,
> etc.
> I only have a draft of this memo;  I have not yet found a copy of the
> complete final version.
> 
> https://drive.google.com/file/d/106a4W2mXsi4Ii-YzRgzsTAwe9_34IqJg/view?usp=sharing
> 
> --To further describe the operational state of the PUP Internet in the
> Spring of 1976, though, I have also found a copy of the then-current text
> file used to define assigned network numbers, host numbers, well-known
> sockets, and name-to-internet-address mapping.  This file was used to
> initially configure the gateways, and to load the name server.  The Tenex
> header shows this as the 50th copy of the file that was created --
> PUP-NETWORK.TXT;50, dated March 19, 1976.
> It shows that the PUP Internet at that time included 2 Ethernets, 2 MCAs,
> and the Arpanet.
> Well-known Sockets were defined for Telnet, Gateway-Info (routing updates),
> FTP, Misc. Services (name, time, etc.), and Echo.
> The name server database allowed a machine to have multiple names (e.g.,
> MAXC = Maxc1 = Parc-Maxc), and multiple internet addresses (if connected to
> more than one network).
> I count 27 Novas on the PUP Internet at the time.  This includes 3 machines
> acting as Gateways:
>   --The Portola Gateway, on both Ethernets, one MCA, and the Arpanet,
>   --The front end to the MAXC time sharing system, on one Ethernet, both
> MCAs, and the Arpanet.
>   --A Nova on one Ethernet and one MCA.
> There were 7 Novas only on one Ethernet (including a machine for font
> design and two for laser printer units).
> The remaining 17 Novas had both Ethernet and MCA interfaces (but were not
> necessarily running as Gateways).  These included Novas configured as
> servers controlling the older XGP printer,  the newer EARS laser printer,
> the Woodstock File System (WFS), and others.
> There were also 67 individual Altos on the Ethernets.  Most of these were
> for personal use, but the list also included one Alto as a dedicated Data
> Line Scanner system (i.e., a TIP, for in-bound and out-bound terminal
> traffic).
> [My hand-written notes suggest that there were at least 9 other Altos in
> our group which were not in the database (including mine).  Even if no one
> could find them via the name server, they could operate as client machines
> on the PUP Internet.]
> This system was in regular use, day and night, with over 100 machines on 5
> networks of 3 types.
> 
> https://drive.google.com/file/d/1SZ6yRLp6UqpbFKxbKK4D2stB6BcBX5qq/view?usp=sharing
> 
> 
> That was the state of the first and largest operational Internet in March
> 1976, 5 months before the important 2-net SRI demo of the TCP Internet.
> 
> John
> 
> PS:  A few additional notes and quick lessons from that period.
> 1.  For some software-intensive projects a smaller team can be very
> productive.  There may have been ~6 of us helping and kibitizing, but the
> vast majority of the programming and documentation was done by Taft and
> Boggs.
> 2.  As best we could, we did try to share some of our general progress with
> others.
> --I had been full-time at PARC since 1971, but had also been encouraged to
> "try to get a quick PhD" at Stanford.  I took part in Vint's networking
> seminar.
> --In the Spring of 1976 (before the 2-network demo at SRI), three of us
> from Parc were enrolled in a Systems Programming class being taught by
> Vint.  We had to do a group programming project, so the 3 of us undertook
> implementation of the 2nd generation simple file transfer:  evolving from
> the Ethernet-based EEFTP (written in Nova assembler) to a new
> internet-capable Pup-based EFTP (written in BCPL).  We turned in the
> listings, complete with some packet traces (from an Ethernet watcher) to
> show how it worked.  We all got an A+ -- thank you, Vint!
> --Later, Vint graciously arranged for us to attend some of the TCP working
> group meetings.  In July 1977 (before the 3-network demo) Yogen Dalal (who
> had been a graduate student under Vint) and I attended a TCP Working Group
> meeting held at MIT.  Jon Postel's TCP Meeting Notes (later registered as
> IEN 65) reflected some of our overview:  "PARC has 5 different networks
> with peices [sic] in Palo Alto, Los Angeles and various places on the East
> Coast.  Approximately 14 different networks, approximately 300 hosts
> connected."
> --In the following month, Aug. 1977, we attended an Internet meeting at ISI
> -- where we mentioned our gateway routing, gateway services,
> naming/addressing/routing, etc. [IEN 3] [IEN 19] [IEN 20]
> --Later, with the help of Don Nielsen and the crew at SRI, we became users
> of the PRNet -- adding it as a network in our internet, carrying
> encapsulated Pups wirelessly between two Pup gateways.  This was reported
> in IEN 78, https://www.rfc-editor.org/ien/ien78.pdf
> 3.  At this time the TCP Internet was designed to expose a reliable byte
> stream interface.
> The PUP Internet architecture provided interfaces at multiple levels:
> --Reliable byte stream (BSP), used for Telnet, FTP, etc.
> --Reliable packet stream (EFTP), used for simple file transfer, esp. to a
> print server.
> --Raw packet access, for very simple tasks (name server, time server, echo,
> etc.)
> Two years later, in 1978, the split of TCP into TCP and IP eventually
> allowed that kind of flexibility.
> 4.  Network-relative addresses were used in both the TCP Internet and the
> PUP Internet, with a network ID and a host ID.  This worked OK in the early
> days of both TCP and PUP, but we quickly realized that a) this did not work
> well if you wanted to move a machine from one network to another, and b)
> this would not scale adequately.  We tried to learn from both the
> Experimental Ethernet and the PUP Internet.  Thus, Yogen Dalal developed
> the 48-bit flat address space -- used in what became the 2nd generation DIX
> Ethernet standard, and used in the 2nd-generation Xerox Network Systems
> (XNS) protocols.  The 48-bit Ethernet address design has scaled and endured
> for ~50 years -- great work by Yogen.
>   https://dl.acm.org/doi/epdf/10.1145/800081.802680
>