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

[Vint Cerf]

there is no question about this - he was charged with implementing on
LSI-11/23

v


On Mon, Feb 9, 2026 at 6:39 PM Don Nielson <nielsonz at pacbell.net> wrote:

> I should have affirmed that Jim Mathis was almost certainly responsible
> for the TCP process in the TIU.  Don
> Sent from my iPhone
>
> On Feb 9, 2026, at 4:33 AM, Vint Cerf <vint at google.com> wrote:
>
> 
> thanks Don!! we were trying to figure out early efforts at bridging
> networks - PRNET was a key project for exploring that concept.
>
> v
>
>
> On Mon, Feb 9, 2026 at 3:46 AM Don Nielson <nielsonz at pacbell.net> wrote:
>
>> Vint, Barbara, and all,
>> I'm not sure I understand the impetus for all this but thought I'd try to
>> help pin down some dates in the early use of the TIU and TCP.
>>
>> The first I could find was in a Packet Radio Quarterly Report covering
>> 1 May 1976 to 31 July 1976.  During that time a gateway was in the
>> station computer and was first just doing header swaps between the
>> ARPANET and the PRNET.  But in the same period the LSI-11 TIU was
>> there running a single-connection user version TCP.  Rather that try
>> to describe what was written, I've attached three images of the report
>> and the text.  Reference to the description of the TIU architecture
>> also included Dave Retz as the lead author so his hand was in it
>> as well, probably more to do with the MOS operating system and
>> the ELF processes working there.  I've also attached a process
>> diagram of the TIU circa Feb 1977.
>>
>> Hope this helps.
>> Don
>>
>>
>>
>>
>> On 2/5/26 4:10 AM, Vint Cerf wrote:
>>
>> 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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>>
>>
>> --
>> Please send any postal/overnight deliveries to:
>> Vint Cerf
>> Google, LLC
>> 1900 Reston Metro Plaza, 16th Floor
>> Reston, VA 20190
>> +1 (571) 213 1346 <(571)%20213-1346>
>>
>>
>> until further notice
>>
>>
>>
>>
>>
>
> --
> Please send any postal/overnight deliveries to:
> Vint Cerf
> Google, LLC
> 1900 Reston Metro Plaza, 16th Floor
> Reston, VA 20190
> +1 (571) 213 1346 <(571)%20213-1346>
>
>
> until further notice
>
>
>
>

-- 
Please send any postal/overnight deliveries to:
Vint Cerf
Google, LLC
1900 Reston Metro Plaza, 16th Floor
Reston, VA 20190
+1 (571) 213 1346


until further notice