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

[Vint Cerf]

Jim Mathis did the TIU system - must have been circa 1975/1976
vint


On Thu, Feb 5, 2026 at 1:01 AM Greg Skinner via Internet-history <
internet-history at elists.isoc.org> wrote:

> 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
> >
>
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