[ih] when did APRANET -TIPs become known as -TACs
John Day
jeanjour at comcast.net
Mon Sep 29 05:40:21 PDT 2025
Yes, the PTTs went for protocol translation which is what the did traditionally, which everyone knew could be a really messy ugly n^2 problem. Whereas, in 1972 when INWG was formed, Pouzin pointed out that by changing the name of the Transport Layer to Internet Transport Layer and treating it as an overlay, the problem disappeared. All the individual networks had to do was support the minimal service assumed by the Internet Transport Layer.
John
> On Sep 29, 2025, at 01:30, the keyboard of geoff goodfellow <geoff at iconia.com> wrote:
>
> another aspect of "The PTT vision" was that of different type/kind of "split with respect to "settlements" for "the connection time, distance and characters transmitted" where indeed "the TCP/IP suite was that it did not include such a split" the X.25/X.75 networks divvied up/"shared" the "loot" between them -- just like was done for long distance toll calls between intra country carriers/regions as well as inter country/internationally...
>
> it's worth additionally noting that there was an "attempt" to "import" (a polite way of putting it :) and implement the PPT intercarrier revenue "settlements" splitting into/into the Internet with/by ANS CO+RE..., viz.:
>
> Data Network Raises Monopoly Fear
> By JOHN MARKOFF
> The New York Times
> December 19, 1991
> http://www.nytimes.com/1991/12/19/business/data-network-raises-monopoly-fear.html
>
> g
>
> On Sun, Sep 28, 2025 at 6:00 PM Brian E Carpenter via Internet-history <internet-history at elists.isoc.org <mailto:internet-history at elists.isoc.org>> wrote:
>> The PTT vision was based on a monopoly charging for connection time, distance and characters transmitted. X.25 plus X.75 fitted that vision well. Remember that there was a long period during which Judge Greene's ruling applied in the US, but the traditional monopolies were still in place in Europe (and Asia). That's why US GOSIP was so different from European GOSIP, so OSI was split into two visions. The main attraction of the TCP/IP suite was that it did not include such a split.
>>
>> Regards/Ngā mihi
>> Brian Carpenter
>>
>> On 29-Sep-25 12:13, John Day via Internet-history wrote:
>> > I am sorry Jack, but X.25 was the bane of OSI forced on it by the PTTs. It was part of PTT vision, but everyone knew it was a dead-end and had been since 1976, when it first appeared. It epitomized what was wrong with PTT-think. They had no clue about networking and still don’t.
>> >
>> > The OSI vision was, if anything, Ethernet (an ISO standard), CLNP, TP4, and ACSE.
>> >
>> > Take care,
>> > John
>> >
>> >> On Sep 28, 2025, at 18:14, Jack Haverty via Internet-history <internet-history at elists.isoc.org <mailto:internet-history at elists.isoc.org>> wrote:
>> >>
>> >> Hi Barbara,
>> >>
>> >> X.25 made it easier to connect hosts to IMPs. ARPA had funded lots of computers used in the research community to have someone build 1822 interfaces. But there were lots of other computers used outside the research environment. X.25 was a key part of the OSI vision, and computer manufacturers were much more likely to create an X.25 interface for their products than an 1822 interface.
>> >>
>> >> I don't think this really affected the choice of IMPs versus directly connecting routers with wires. Part of an X.25 interface was the basic physical connection for a wire, and it was straightforward to just interconnect routers with a wire by using that same physical interface with no X.25 connection management sofware needed.
>> >>
>> >> At one point at BBN we noticed that a wire was really just a very basic "network" that could be used to interconnect gateways. A wire was effectively a "class F" network with just 2 possible attached computers - "this end" and "the other end". We actually tried connecting two gateways together with a wire instead of using the ARPANET and it worked fine.
>> >>
>> >> At one point (can't remember exactly when) I was responsible for "DDN System Engineering", and frequently got called to Washington for various meetings. One of them was to hear some startup's pitch for how DDN could use their products. After the pitch, everyone turned to me and the guy in charge asked "Will this work?". I think they expected me to say it was a silly idea and they really needed to use BBN's solutions. But, as a DDN consultant, I said "Yes, it should." They got a testbed running, and the startup no doubt realized the same thing that we (and SRI later) did - you didn't really need the IMP in the picture. BTW, that startup was Cisco Systems.
>> >>
>> >> I'm not sure when I first heard PSN as the acronym for Packet Switched Node. My recollection is that the terminology came out of the OSI vision which had become very popular. IMP stood for Interface Message Processor but that name was always confusing. I remember there was an IMP somewhere with a clipping pasted on its front panel -- a message had come in from a US government Senator, congratulating someone (ARPA? BBN?) on their successful creation of the "Interfaith Message Processor" (read the last three words carefully). There's a writeup at https://foxmancommunications.com/the-interfaith-message-processor-and-the-tower-of-babel/
>> >>
>> >> It was an interesting time.
>> >>
>> >> Jack
>> >>
>> >> On 9/28/25 12:19, Barbara Denny via Internet-history wrote:
>> >>> Do you think the obsolescence of 1822 in favor of X.25 just made it easier to get rid of IMPs in the networks?
>> >>> I am thinking about the military testbed for USAREUR where I think the original deployment had CXXs (don't remember if it had C30s or C70s but leaning towards C30s). It was deployed in that timeframe. It originally had IMPs and Cisco AGS routers but I think SRI pulled the IMPs and just used the routers very soon after it was originally installed.
>> >>> BTW, what is the story for replacing the IMP term for PSN (Packet Switching Node) and when was this done?
>> >>> barbara
>> >>> On Sunday, September 28, 2025 at 10:08:29 AM PDT, Jack Haverty via Internet-history<internet-history at elists.isoc.org <mailto:internet-history at elists.isoc.org>> wrote:
>> >>> On 9/28/25 06:31, Noel Chiappa via Internet-history wrote:
>> >>>> > From: Jack Haverty
>> >>>>
>> >>>> > Much of this history was probably well-documented in the reports
>> >>>> > submitted by BBN ... It may be available on discover.dtic.mil <http://discover.dtic.mil/>
>> >>>>
>> >>>> I took your suggeation, and turned up an answer to one question: there
>> >>>> were C/30-based TACs, as well as one-time-TIP-based TACs.
>> >>>>
>> >>>> Combined Quarterly Technical Report No. 22
>> >>>> https://apps.dtic.mil/sti/pdfs/ADA104931.pdf
>> >>>> Combined Quarterly Technical Report No. 23
>> >>>> https://apps.dtic.mil/sti/pdfs/ADA108783.pdf
>> >>>> The DDN (Defense Data Network) Course
>> >>>> https://apps.dtic.mil/sti/tr/pdf/ADA173472.pdf
>> >>>>
>> >>>> I found nothing about what physical interface any of them used, though,
>> >>>> but I'll bet it was an 1822.
>> >>>>
>> >>>> Noel
>> >>> Hi Noel,
>> >>>
>> >>> Yes, good detective work. There's lots of information in contractor
>> >>> reports. At every Internet Meeting there were a lot of contractors, so
>> >>> the reports from each were limited to 15 minutes or so. Much of the
>> >>> detail wasn't even presented in the meetings, and of course not captured
>> >>> in Jon's minutes.
>> >>>
>> >>> There's lots of technical detail in those old reports that probably
>> >>> should have been issued also as RFCs or IENs. The reports went to
>> >>> various parts of the government, and to the people inside BBN who had
>> >>> worked on the projects, but probably not much beyond those groups. For
>> >>> example, I assume all the other ARPA contractors had to submit similar
>> >>> reports. But I don't recall ever seeing a report from SRI, MIT, UCLA,
>> >>> Linkabit, Collins, or any of the other contractors who attended the
>> >>> various Internet meetings. I still haven't seen more than a handful of
>> >>> non-BBN reports, but I suspect some might be in DTIC.
>> >>>
>> >>> At some point I was given responsibility for all of the ARPA and related
>> >>> contracts in our part of BBN. That meant I became the "author" of the
>> >>> BBN reports. Pragmatically what it meant was that I had to badger all
>> >>> of the project leaders to write down what their teams did during the
>> >>> quarter. Getting blood out of a stone would have been easier than
>> >>> getting documentation out of an engineer. For many of our contracts,
>> >>> the only required deliverables were the Quarterly Reports. Until the
>> >>> Report was submitted, the government wouldn't pay the bill.
>> >>>
>> >>> BTW, re C/30 et al. Internet History has probably never been told about
>> >>> that part of the history:
>> >>>
>> >>> The C/30 hardware was based on a BBN project called the MBB -
>> >>> Microprogrammable Building Block. As the name implies, the hardware was
>> >>> microprogrammable. The C/30 microcode was designed to make an MBB look
>> >>> exactly like a Honeywell 316. So the same code that had been developed
>> >>> for the 316-based IMPs (or TIPs) would also run on a C/30.
>> >>> Effectively, a C/30 looked exactly like a Honeywell 316 to the software
>> >>> that ran on it.
>> >>>
>> >>> Similarly, a C/70 was a Unix minicomputer also built on an MBB, but with
>> >>> an interface to disk storage and probably more RAM. The MBB microcode
>> >>> used for a C/70 was optimized for code written in the C language, which
>> >>> was the language used by the Unix OS.
>> >>>
>> >>> BBNCC started life as BBN Computer Corporation, with a plan to sell Unix
>> >>> boxes to the world. Competing with DEC was probably always a bad idea,
>> >>> so later BBNCC became BBN Communications Corporation, selling IMPs to
>> >>> the marketplace as ARPANET clones, and a few C/70s operating as NOCs.
>> >>> Didn't even have to change the logo.
>> >>>
>> >>> There was also a C/60, but I can't remember what it did.....
>> >>>
>> >>> There's probably lots of detail in other old BBN reports, as well as
>> >>> reports from others. For example, I just searched in DTIC for "BBN MBB"
>> >>> and found this discussion about formal verification of the C/30
>> >>> microcode:https://apps.dtic.mil/sti/tr/pdf/ADA510573.pdf -- which
>> >>> even found bugs in the microcode. Another timeline bit in that report -
>> >>> the 1822 interface was obsolete on DDN by 1986, in favor of X.25 for the
>> >>> Host/IMP interface.
>> >>>
>> >>
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>
> --
> Geoff.Goodfellow at iconia.com <mailto:Geoff.Goodfellow at iconia.com>
> living as The Truth is True
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