[ih] ARPANET uncontrolled packets (was: GOSIP & compliance)

[vinton cerf]

i think the point about the type 0 subtype 3 is that they may not have been
reassembled and might have had limits as to size (unlike the 8000 bit
"message"). As I recall they were "uncontrolled" which means the space
reservation protocol was not in force for them. Since these were used for
voice (and maybe video), they might have been limited to single packet size
(1000+ bits) and were not assured of delivery.

Steve Casner, any more specifics? Copying Bob Kahn in case he is not on the
internet-history list

v


On Mon, Apr 4, 2022 at 12:27 PM Jack Haverty via Internet-history <
internet-history at elists.isoc.org> wrote:

> Guilty!  I've always found it difficult to get the correct terminology.
>
> Actually, thinking and remembering a bit more, to be even more precise
> those "type 0, subtype 3" globs of bits weren't "packets" either.   They
> were "messages", passed back and forth between a Host and its attached
> IMP.   The IMP carved those messages up and put the data into one or
> more "packets" which were what actually got sent over the wires.
> Actually, there may have been more technical chicanery involved there,
> with things like "frames" in the mix.  At the final IMP in the path, all
> those "packets" were "reassembled" and the data delivered to the Host in
> "messages".   But I don't recall if the receiving Host could tell that
> an incoming message was sent out as a type 0, subtype 3 from the
> transmitting Host.
>
> IIRC, it was the IMP-to-IMP packets which were uncontrolled, and handled
> outside the normal mechanisms of error control, flow control, congestion
> control, etc.  I don't think I ever knew exactly how all that worked --
> but the old IMP code is available online should anyone be curious.
>
> Then of course if you looked more closely, you might see that the TCPs
> involved were sending and receiving data from their users' application
> programs.  At one point there were even "Letters" passing across that
> interface, which the TCP would carve up into "datagrams", which it might
> supply to an attached ARPANET port as "messages".  Somewhere down the
> path, a Gateway might receive a message, determin that it wouldn't fit
> into the next network, so it would carve up the datagram into
> "fragments", which were themselves smaller datagrams, leaving putting it
> all back together as a challenge for the TCP running in the Host at the
> ultimate destination.
>
> Complicating things even further, if the applications involved were
> transferring electronic mail, they would be also accepting "messages"
> from human users, carving them up into "letters" for TCP, which would
> carve them up into "datagrams", which might become a string of a
> different kind of "messages", which might become a gaggle of "packets",
> with "fragments" spontaneously appearing in the fray from time to
> time.   The life of a bit in its travels through the Internet is crazy
> and frenetic.   Ask any bit which has gotten discarded along the way and
> now lies in a bit bucket somewhere in the net.
>
> There just weren't enough words to precisely describe the carnage
> involved in computer networking...reminds me of those old late-night TV
> ads "It slices, it chops, it dices, it shreds!  Call this number to
> order your Acme Kitchen Wizard!  Call now and get two for the price of
> one!"
>
> Jack Haverty
>
>
>
>
> On 4/3/22 22:58, Stephen Casner wrote:
> > On Sun, 3 Apr 2022, Jack Haverty via Internet-history wrote:
> >
> >> UDP defined a "datagram mode" somewhat analogous to the ARPANET's
> >> "uncontrolled packets" ("type 3" IIRC).  The ARPANET operators at BBN
> were
> >> staunchly opposed to allowing such packets to be used, for fear that
> they
> >> would seriously disrupt the normal "virtual circuit" mechanisms
> internal to
> >> the ARPANET structure.  So "datagrams" on the ARPANET, while possible,
> were
> >> only rarely permitted, for specific experiments, between specific Hosts.
> > I have often seen/heard the ARPANET uncontrolled packets referenced as
> > "type 3", e.g. by our late Danny Cohen.  But they were actually "type
> > 0, subtype 3".  I remember implementing that for packet voice.  Check
> > BBN 1822 pp. 3-14 and 3-35.
> >
> >                                                          -- Steve
>
> --
> Internet-history mailing list
> Internet-history at elists.isoc.org
> https://elists.isoc.org/mailman/listinfo/internet-history
>