[ih] The origin of variable length packets

[Dave Walden]

At 07:50 PM 2/28/2011, Noel Chiappa wrote:
>I would assume/guess that the first well-known and wide-scale use was in the
>ARPANet.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)

>Hi,

I'm not close to home right now, so I can't look up what ARPA's call 
for bids (RFQ) to develop the ARPANET IMP's specified.  I sort of 
feel that it already specified that the host computers could send 
messages that were variable length up to about 8,000 bits, and the 
packet-subnet of IMPs broke these messages into about 1,000 bit 
packets with the last packet in a message being possibly being 
shorter than a full 1,000 bits.  Anyway, that's the way, as I 
remember, that we initially implemented it in the IMPs.  I do 
remember that there was a preconception of bi-modal message traffic 
with file transfers being broken into 8,000 bit messages, and 
interactive terminal traffic being messages of only 10s or 100s of 
bits, i.e., one packet or less.  I also think I remember that the (I 
think 24-bit) CRC on inter-IMP packets was calculated to have the 
desired error detection rate based on 1,000 bit packets.

Dave



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