[ih] principles of the internet

[John Day]

I remember that as well, but not from the first hand experience that you do.

But I do remember seeing a paper that quoted line error rates and 
being struck by the fact that the longest links in the net had some 
of the lowest error rates while the shorter ones were much higher.

In particular I remember that Illinois to Utah (one hop) had almost 
no errors, but Rome NY to Boston also one hop had one of the highest 
error rates!  But I assumed that the latter went through much older 
equipment and than the former.

At 18:21 -0400 2010/06/01, Bernie Cosell wrote:
>On 1 Jun 2010 at 17:31, Noel Chiappa wrote:
>
>>  The big change going from the ARPANET (not Host-Host Protocol, see above) to
>>  the Internet (in terms of the _placement_ of function - the 
>>Internet of course
>>  added other capabilities, such as being able to use a diverse range of
>>  technologies, but that's different) was to make the hosts responsible for
>>  reliable transmission (checksums, sequence numbers, timeouts,
>>  retransmissions).
>
>I have an odd perspective on this and it seemed to me that the thrust for
>this kind of change was that the phone lines were *MUCH* better than we
>expected them to be [and the current fiberoptic links are even better].
>
>When Bob Kahn cobbled up the checksum equation the IMPs were to use over
>the 50Kb circuits, it was assumed that the lines would be pretty much
>full all the time and that the lines would perform according to AT&T's
>specs.  (and indeed we even calculated [but I can't remember the details
>any more] how often a broken-but-undetected packet would get through)  It
>was very conservative and checksummed hop-to-hop [since if you expect a
>lot of errors, that's more efficient that sending it all the way to the
>other end only to discover that it got broken back at hop-1].  But we
>quickly discovered that the reality was we had almost *no*
>retransmissions and while that didn't cause any change right-off [since
>the modems were still generating and checking their 24-bit checksums and
>the IMPs were dutifully retransmitting hop-by-hop] it *DID* indicate that
>a change in the direction of end-to-end would likely result in much
>better throughput than hop-to-hop.
>
>   /Bernie\
>
>--
>Bernie Cosell                     Fantasy Farm Fibers
>mailto:bernie at fantasyfarm.com     Pearisburg, VA
>     -->  Too many people, too few sheep  <--