[ih] principles of the internet

[Matthias Bärwolff]

On 06/03/2010 05:10 PM, Dave Crocker wrote:
> 
> 
>>> The complexity of the Arpanet design and layering might permit a bit of
>>> debate about whether it qualified as being based on best effort.
>>> Alohanet's simplicity does not (permit debate.)
>>
>> Why not? Alohanet (pure Aloha) capacity was at 1/(2e), and downlink data
>> was not even acknowledged (for performance reasons). Ethernet capacity
>> has been at some 98 percent right away, and packets hardly ever got lost
>> (safe in screwed up installations). Best effort certainly doesn's mean
>> no effort (as in Alohanet), but has probably always meant "reasonable",
>> "sane" effort. (But that's just my two cents, Richard was gonna
>> enlighten us us to the three meanings of best effort.)
> 
> 
> Alohanet was not no effort.  It had retransmission.
> 
> But it merely kept things extremely simple.  That its version of 'best'
> was relatively poor and that the Ethernet's version was a lot better
> does not make either less an example of 'best'.
> 

Just an aside correction: Alohanet only had acknowledgments and
retransmission on the uplink. The broadcast channel (from the central
hub to all stations) had no retransmission as it was considered
reasonably reliable (there could be no collisions, after all). Another
fun fact about the Alohanet: a station would have retransmitted only 2
times, after which it would give up and leave retransmissions to the
user -- the rationale being that this way the third retransmission
interval would be larger and more random so as to avoid yet another
collision. It rarely happened given the fairly low volume use of the
network, but it was in the specs (probably written after the fact, but
anyway).

Matthias

> d/

-- 
Matthias Bärwolff
www.bärwolff.de