[ih] inter IMP hackery [was Recently restored and a small ARPANET was run using simulated IMP hardware, ]

Mon Sep 7 11:15:35 PDT 2020

I too would be interested in learning more.  I believe the IBM 729 mod IV
tape drive operated at 112.5 inches per second.  High density tapes were
556 chars/inch, where a character was six bits.  That works out to 62,500
chars/sec or 375,000 bits/sec.  It would be interesting to know the
transfer rate between MTIPs.

Steve

On Mon, Sep 7, 2020 at 2:06 PM the keyboard of geoff goodfellow via
Internet-history <internet-history at elists.isoc.org> wrote:

> thanks for the clarification on the MTIPs Alex... was always curious as to
> the MTIPs, as they seemed "unique"/"forgotten" in the history of the
> ARPANET and never seemed to get much if any prominence (and now
> understandably given that there were only two of them).
>
> the MTIPs had come to yours truly's attention in that in the Tenex host
> table file, <System>Host-Name/Descriptor-File.txt as well as IIRC in the
> NIC's (SRI-ARC) <Netinfo>Hosts.txt there was a descriptor field of what
> type (i.e. functionality) a given host provided: User, Server, TIP or MTIP.
>
> one remaining question of the MTIPs: did they only transfer data between
> them exclusively over the ARPANET, MTIP to MTIP only, -OR- were they used
> to transfer/send data from a mag tape on an MTIP to some socket & receiving
> process on a "server" host?
>
> if the later, the next curious/pesky question would be: what was the
> protocol (and corresponding socket #) used to effectuate said data
> transference?
>
> geoff
>
> On Mon, Sep 7, 2020 at 6:30 AM Alex McKenzie via Internet-history <
> internet-history at elists.isoc.org> wrote:
>
> >  Geoff,
> > Now that I've refreshed my memory, I can say that the 2 mag tape TIPs
> were
> > installed at Global Weather Central, Offett AFB, NE, and Atmospheric
> > Sciences Lab, Army Electronics R&D Command, White Sands Missile Range,
> NM.
> > As I said in my previous message, the motivation was to allow the two
> > organizations  to experiment with using the ARPAnet to replace whatever
> > method they were using to exchange large amounts of data.  I cannot
> > remember the dates associated with this test, nor can I recall if it was
> > deemed a success.
> > Sorry for the previous mis-information,Alex
> >
> >     On Monday, September 7, 2020, 11:01:20 AM EDT, Alex McKenzie via
> > Internet-history <internet-history at elists.isoc.org> wrote:
> >
> >   Geoff,
> > There were two mag tape TIPs, at Tinker and McClellan Air Force Bases.
> > The motivation was to allow the Air Force to experiment with using the
> > ARPAnet to replace whatever method they were using to exchange large
> > amounts of data.  I think the test was successful and Tinker and
> McClellan
> > then decided to attach Hosts to the TIPs to continue operational use of
> the
> > net to do their data exchanges.  Steve Crocker was involved in helping
> the
> > Air Force people design the Host software to use the ARPAnet, which led
> to
> > an amusing story which Steve has recounted several times (it crashed the
> > network, and one of the BBN people decided it was deliberate).  As I
> recall
> > the test was run in the summer of 1972 and shortly after that the mag
> tape
> > hardware and software stopped being supported by BBN.
> > Cheers,Alex
> >
> >     On Sunday, September 6, 2020, 9:05:33 PM EDT, the keyboard of geoff
> > goodfellow via Internet-history <internet-history at elists.isoc.org>
> > wrote:
> >
> >  Dave (or Bernie), can you provide any elucidation on the ARPANET MTIPs
> > (the
> > TIPs that had a magnetic tape unit attached to them)?
> >
> > yours truly kinda recalls there were perhaps two of them... one being at
> > GWC?
> >
> > why were they created and to whom did they send their data?
> >
> > geoff
> >
> > On Sun, Sep 6, 2020 at 2:50 PM dave walden via Internet-history <
> > internet-history at elists.isoc.org> wrote:
> >
> > > I can describe the genesis.  The IMP code was originally for one host
> > > computer and several inter-IMP modems (that was what our contract
> > > specified), and I coded the IMP/Host and Host/IMP code for that in
> > > parallel with Bernie coding the DDT, etc. Then some host site wanted a
> > > second host on its IMP -- I think maybe UCLA for its IBM 360.  ARPA
> > > called us and asked if the IMP could handle more than one Host.  Our
> > > hardware guys said the Honeywell computer could support (if I remember
> > > correctly) up to seven interfaces which could be up to four Host
> > > interfaces or up to four inter-IMP modem interfaces.  We looked at the
> > > IMP/Host and Host/IMP code and it seemed fairly easy to make it
> > > reentrant, so we told ARPANET "yes".  Once the IMP would know how to
> > > handle multiple Hosts and given there was a bit in the header words
> > > between IMPs and Host to say "real" Host or "fake" Host, the
> > > possibilities were fairly clear.  I implemented the reentrant IMP-host
> > > and host-IMP code, and Bernie changed the routines he had written or
> was
> > > writing:
> > > - TTY in/out
> > > - DDT in/out
> > > - parameter change packets into the IMP and trace packets out of the
> IMP
> > > - into the IMP to be discarded and statistics packets out of the IMP
> > > For the regular reports from IMPs to the Network Monitoring Center, a
> > > bit of code in the IMP could send packets to a real host; I don't
> > > remember which of the fake Hosts they looked like they were coming from
> > > -- stats maybe.
> > >
> > > On 9/6/2020 7:30 PM, Bernie Cosell via Internet-history wrote:
> > > > Early on as we were coding the IMP stuff the question arose as to
> what
> > > to do
> > > > about the TTY [and how the hell were we to debug the damn thing].  We
> > did
> > > > several things in this regard.  First I wrote a simple DDT [about as
> > > powerful as
> > > > the test-word switches on our PDP-1 :o)] but it allowed us to poke
> > > around in the
> > > > dead hulk of the code of a stopped system to see what went wrong and
> > > also put
> > > > patches in.  I believe it was originally a stand alone - the imp
> would
> > > crash or hit a
> > > > diagnostic trap and they we could run the DDT and look at buffers and
> > > counters
> > > > and pointers and such and generally try to figure out what happened.
> > > When the
> > > > IMP was running solidly enough [which actually happened pretty early
> on
> > > in its
> > > > development],  I can't remember the genesis of the underlying idea,
> > > but  we
> > > > thought we could route the DDT *over* the net to other IMPs and poke
> at
> > > *then*.
> > > > I came up with a scheme that Will [I think] thought was way too
> > > complicated:
> > > >
> > > >
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> > >
> > >
> >
> > --
> > Geoff.Goodfellow at iconia.com
> > living as The Truth is True
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> >
> >
>
> --
> Geoff.Goodfellow at iconia.com
> living as The Truth is True
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