[ih] principles of the internet

[Richard Bennett]

Metcalfe's Ethernet was the canonical best-effort network, with a single 
service level and no point to point retransmission, although it did 
automatically retransmit following collisions using the truncated binary 
exponential backoff algorithm that was later adopted in a moderately 
different form by Jacobson's Algorithm in TCP. Modern hub and spoke 
"Ethernets" don't have collisions, retransmission, or single service 
level, but they do have flow control.

I've always thought it interesting that TCP seeks to mimic the behavior 
of the layer 2 protocol most commonly in use, whatever it may be at any 
given time, and that analysts often mistake particular forms of this 
mimicry for fundamental design elements when in fact the actual 
principle is reflection. Network engineering is too close to the process 
of making things work to understand all the motivating factors - it's 
like trying to write your own biography and expecting it to be objective.

On 6/1/2010 5:46 PM, John Day wrote:
> At 22:54 +0200 2010/06/01, Matthias Bärwolff wrote:
>> On 06/01/2010 10:00 PM, Dave Crocker wrote:
>>>
>>>
>>>  On 6/1/2010 11:49 AM, Richard Bennett wrote:
>>>>  The Internet protocols are agnostic about privilege and 
>>>> best-effort, as
>>>
>>>  Absent standardized QOS, IP is best effort and the transport-level
>>>  reliability mechanisms reflect this, even as weak as they were
>>>  (intentionally) made to be.
>>
>> Best effort to me seems absolutely central to the "Internet
>> architecture" -- I'd recommend reading Metcalfe's thesis' chapter 6
>> which really nicely elaborates the notion.
>
> This is the contribution from Pouzin implemented in CYCLADES, which 
> Metcalfe picks up on for the more limited environment of the LAN.
>
>>
>>>
>>>  This was a major shift from the degree of delivery assurance attempted
>>>  for the Arpanet IMP infrastructure, which was reflected in the 
>>> /lack/ of
>>>  host-to-host reliability mechanism in the NCP.
>>>
>>>
>>>>  these are layer two functions that are simply outside the scope of a
>>>
>>>  Except that layer two is not end-to-end and therefore cannot make
>>>  end-to-end service assertions or enforce them.
>>>
>>>
>>>>  I don't know that economics has much to do with this, beyond the
>>>>  assumption that packet-switching is more economical for 
>>>> human-computer
>>>>  interactions than circuit-switching is. The Internet wasn't 
>>>> designed by
>>>>  economists.
>>>
>>>  Cost-savings, by avoiding NxM combinatorial explosion of 
>>> communications
>>>  lines, was an explicit and frequently cited motivation for the 
>>> work, at
>>>  least in terms of what I heard when I came on board in the early 70s.
>>
>> +1 the avoidance of the nxm problem is all over the literature from the
>> time (also, Padlipsky's term "common intermediary representations" comes
>> to mind)
>
> This use of n x m is very different than Dave's use about 
> connectivity.  This is the concept that was called the canonical 
> form.  It was critically important in the early network, but actually 
> proves to be a transitional concept.  It is absolutely necessary when 
> the same application is developed in isolation: terminals, file 
> systems, etc.  But once networks become common, new applications are 
> designed from the start to be used on different systems over a 
> network.  So they are their canonical form.
>
> I always thought this was quite interesting. Since at one time, it was 
> trying to formalize the idea of canonical form is what drove me to 
> reading too much Frege.  ;-)  Then to find out, that the existence of 
> the network makes the problem go away was amusing.
>
>> >
>>>  Surviving a "hostile battlefield" was the other, which meant
>>>  conventional, not nuclear, conditions.  At the time, I believe folks
>>>  didn't quite anticipate that commercial communications environments
>>>  would also look pretty hostile...
>>>
>>>
>>>  d/
>>
>> -- 
>> Matthias Bärwolff
>> www.bärwolff.de
>
>

-- 
Richard Bennett
Research Fellow
Information Technology and Innovation Foundation
Washington, DC