[ih] The origin of variable length packets

[John Day]

That was amusing.  Another of ITU's attempts to do circuit switching 
as packet switching.

At 9:29 -0500 2011/03/01, Vint Cerf wrote:
>anybody for ATM? :-)
>
>v
>
>
>On Tue, Mar 1, 2011 at 7:25 AM, John Day 
><<mailto:jeanjour at comcast.net>jeanjour at comcast.net> wrote:
>
>Undoubtedly, this is correct.
>
>But it also occurred to me that this was not such a big deal and was 
>probably discovered by everyone who went to build one.
>
>Sending fixed length packets would be more work (or as much work) as 
>sending variable length ones!  In both cases, you need a length to 
>indicate how much data is there.  But in the fixed length case you 
>have to send more bits than you need and fill out the packet with 
>zeros.
>
>Wastes bandwidth and is more work. Not a lot more, but in those days 
>one saved everyplace you could!
>
>The historians should remember that for engineers, Laziness is a 
>virtue!  ;-)  Not everything that looks like a major insight to the 
>historians was.  Much of it was just common sense.
>
>Anyone who went to build it would have done the same thing.
>
>Baran's emphasis was that data was not voice.  Voice networks send 
>streams of fixed length frames, e.g. T-1, because they are 
>continuously sampling sound.  Data is going to be very different.
>
>
>At 22:50 -0500 2011/02/28, Noel Chiappa wrote:
>
>    > From: Stephen Suryaputra <<mailto:ssurya at ieee.org>ssurya at ieee.org>
>
>    > Any pointer or reasons why the packet becomes variable length later on?
>
>I would assume/guess that the first well-known and wide-scale use was in the
>ARPANet. (Which was pretty much the first general packet network I know of -
>were they any proprietary things before that, does anyone know?)
>
>The first variable length data items transmitted between compturers (although
>I would tend to doubt they thought of them as packets) might be hard to track
>down.
>
>It might have been some of the early computer-computer experiments, e.g. the
>kind of thing Larry Roberts did at Lincoln Labs (which definitely had variable
>length messages); another early system that might have had variable length
>data items was SAGE (since that also had computer-computer links between
>centers, although I don't know offhand of a source that talks about that level
>of detail on the communication aspects of SAGE).
>
>
>    > A reference would be really appreciated.
>
>For Larry Roberts' work:
>
>  Thomas Marill, Lawrence G. Roberts, "Toward A Cooperative Network Of
>  Time-Shared Computers", Fall AFIPS Conference, October 1966
>
>For the ARPANET:
>
>  Frank Heart, Robert Kahn, Severo Ornstein, William Crowther, David Walden,
>  The Interface Message Processor for the ARPA Computer Network (1970 Spring
>  Joint Computer Conference, AFIPS Proc. Vol. 36, pp. 551.567, 1970)
>
>For SAGE, although there are a number of things about it, for instance the one
>listed here:
>
>
><http://en.wikipedia.org/wiki/Semi_Automatic_Ground_Environment#Further_reading>http://en.wikipedia.org/wiki/Semi_Automatic_Ground_Environment#Further_reading
>
>Like I said, I don't know of anything there that goes into a lot of technical
>detail on the communication stuff, though. (I looked through a couple,
>including the 'Annals of the History of Computing' issue.) In particular,
>there's a rumor that SAGE had the first email, but the communication part of
>the system especially is so poorly documented in the open literature I've
>never been able to track that down. There is a fair amount on the AN/FSQ-7
>computer, and some on the programming, but the whole communication aspect
>(other than the early radar data transmission) is seemingly not covered
>anywhere.
>
>        Noel
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