[ih] Internet-history Digest, Vol 50, Issue 6

[Vint Cerf]

On Wed, Jan 10, 2024 at 8:07 PM John Day <jeanjour at comcast.net> wrote:

> Packet switching had many advantages, but from the point of view of the
> inventors (Baran and Davies) was the improvement over message switching.
>

no disagreement. I would say improvement over message switching and circuit
switching.

>
> Message switching (and torn tape systems, which message switching was
> emulating) were analogous to the FIFO Batch systems in computers. Short
> messages could get stuck behind long ones. Packet switching was analogous
> to multiprogramming. Short messages were still delayed some, but their
> 'completion time' was much shorter. (Just like in processor scheduling).
> This is what attracted Davies to the idea and must have been noticed by
> Baran, although I haven’t found him mention it explicitly. His focus was
> mostly on survivability and redundancy. But it seems implicit in much of
> what he wrote.
>
> That makes Virtual Circuit, multiprogramming with contiguous (static)
> allocation; and datagrams multiprogramming with dynamic allocation.
>
> And a couple of years later (1968), Denning showed that dynamic was orders
> of magnitude less likely to run out of buffers than static allocation.
>
> Take care,
> John
>
> > On Jan 10, 2024, at 19:38, Vint Cerf via Internet-history <
> internet-history at elists.isoc.org> wrote:
> >
> > thanks John -
> > the last point about speed adaptation is a key value in packet switching
> as
> > long as there is also adequate flow control.
> > The ability to link at different speeds and do store-and-forward is one
> of
> > the major attractions of packet switching.
> > v
> >
> >
> > On Wed, Jan 10, 2024 at 3:26 PM John Shoch via Internet-history <
> > internet-history at elists.isoc.org> wrote:
> >
> >> I've gotten a little behind on the Internet History list.....let me try
> to
> >> catch up.
> >>
> >> John Day:  Thank you for providing more background on Cyclades, and its
> >> underlying transport system, Cigale.
> >> Louis Pouzin's group at IRIA was an early advocate of datagram-based
> >> networking, and had the vision to see the importance of connecting
> diverse
> >> networks into a "catanet" -- although they were not able to implement
> that
> >> in France.
> >> Vint has noted that Gerard Le Lann was a visitor at Stanford (and is
> >> acknowledged on the Stanford Internet Plaque that Vint organized):
> >>  http://ana-3.lcs.mit.edu/~jnc/history/Internet_plaque.jpg
> >> The Cerf/Dalal/Sunshine early draft of a TCP spec., Dec. 1974,
> acknowledges
> >> input from IRIA:
> >> "In the early phases of the design work, R. Metcalfe, A. McKenzie, H.
> >> Zimmerman, G. LeLann, and M. Elie were most helpful in explicating the
> >> various issues to be resolved."
> >>  https://datatracker.ietf.org/doc/html/rfc675
> >>
> >> Dave Crocker:  You noted that, "... I guess PARC was doing
> >> gatewaying/translation between Arpanet/XNS peers...."
> >> Perhaps I can elaborate a little bit:
> >> --PUP was the first generation of internetwork protocols, developed at
> >> Xerox PARC;  XNS was the second generation, primarily developed at Xerox
> >> SDD (building upon what was learned in Pup -- adding large unique
> >> addresses, etc.).
> >> --When the full PUP architecture was first implemented within Xerox, one
> >> could use PUP FTP to move a file from an Alto to an account on PARC's
> >> MAXC/Tenex machine, and one could use Arpa FTP to move that to another
> >> Arpanet host.  I do not think there was a higher-level protocol
> translation
> >> to automatically link PUP FTP with Arpa FTP.
> >> --The Arpanet was added as a network within the PUP architecture, but
> >> primarily as a transit network (as was the Packet Radio Network).  The
> >> encapsulation of PUP internet packets within Arpanet messages is
> described
> >> and diagrammed in the PUP paper by Boggs, et al.:
> >>
> >>
> http://bitsavers.trailing-edge.com/pdf/xerox/parc/techReports/CSL-79-10_Pup_An_Internetwork_Architecture_Jul79.pdf
> >> https://ieeexplore.ieee.org/document/1094684
> >> --When Xerox gave Alto/Ethernet/Dover/PUP systems to a number of
> >> universities (Stanford, MIT, CMU, CalTech, Rochester), I think it
> included
> >> Nova-based PUP "gateways" (which later led to the Stanford/Cisco
> >> multi-protocol routers).  Thus, a user on an Alto at Stanford could use
> PUP
> >> FTP to retrieve a file from a PUP file server at CMU -- and the PUP
> >> internet packets would transit through the Arpanet.  [Xerox, Arpa, and
> the
> >> universities all worked together to enable this.]
> >> --The universities had Xerox PUP file servers;  I don't know if any of
> them
> >> ran the PUP code on their PDP-10s...maybe someone was there?
> >> --XNS came later....
> >>
> >> John Levine made a good observation:  "It occurs to me that it might not
> >> have been obvious that you could run the same network protocol over a
> 56K
> >> DDS line and a 3Mb Ethernet, glue the two together using simple minded
> >> gateways, and it'd work."
> >> --This is, of course, one of the things that motivated the separate
> >> development of Xerox PUP -- we knew that we had to support 3Mbps local
> >> Ethernet connections to file servers and print servers, while also
> >> supporting 9.6 Kbps inter-site leased phone lines.  It was a design
> >> objective, and it had to be made to work!
> >> --Again, from the Boggs paper:
> >> "The communications environment includes several different individual
> >> network designs. The
> >> dominant one is the "Ethernet" communications network, a local-area
> >> broadcast channel with a
> >> bandwidth of 3 megabits per second [Metcalfe & Boggs, 1976]. Long-haul
> >> communication facilities
> >> include the Arpanet, the ARPA Packet Radio network, and a collection of
> >> leased lines implementing
> >> an Arpanet-style store-and-forward network. These facilities have
> distinct
> >> native protocols and
> >> exhibit as much as three orders of magnitude difference in performance."
> >>
> >> Cheers,
> >>
> >> John Shoch
> >> --
> >> Internet-history mailing list
> >> Internet-history at elists.isoc.org
> >> https://elists.isoc.org/mailman/listinfo/internet-history
> >>
> >
> >
> > --
> > 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
> > --
> > Internet-history mailing list
> > Internet-history at elists.isoc.org
> > https://elists.isoc.org/mailman/listinfo/internet-history
>
>

-- 
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