[ih] principles of the internet

[Matthias Bärwolff]

On 06/03/2010 03:17 PM, Dave Crocker wrote:
> 
> 
> On 6/2/2010 1:56 AM, Matthias Bärwolff wrote:
>> Pouzin's contribution notwithstanding, Metcalfe's thesis' chapter 6 to
>> me is the first proper elaboration of best effort as a philosophy;
> ...
>> To my knowledge, Pouzin has never put it that clearly in writing.
> 
> 
> I think one of the other postings made a comment similar to what I'm
> going to say here, but just to underscore my own sense of that period:
> 
> It was quite common for things to be documented very much post hoc. 
> This gives a highly skewed view to diligent historians reading the
> literature, but it makes near-term efforts at oral history particularly
> valuable.

I appreciate this point. (Which is one of the reasons I keep hitting
this list with my questions.) Without heavy triangulation and extreme
caution it is hard to draw meaningful conclusions. (And sure enough
there have been plenty of failed attempts in the secondary literature.)

> 
> One of the issues emerging from some of the sub-threads in this exchange
> is the need to be clear and precise about the application of a term or
> concept.  Given all the layering that these systems have/had, one layer
> might have had a property that another did not.  (For example, Arpanet
> IMP was classic stateless packet/message model, while NCP was virtual,
> end-to-end circuits.)
> 
> This certainly means that debate, about whether a particular
> characteristic was present in a particular system, needs to be specific
> about the specific /part/ or layer of the system that did or did not
> have the characteristic.

To return to my initial go with the list of principles, let me put
forward a revised version applicable to the classic definition of the
Internet ("roughly transitive closure of IP-speaking systems"):

The classic end-to-end arguments (as exemplified by the case of file
transfer to the standard of the application ends, not the more fuzzy
reasonings about possibly excessive efforts in the network to the
detriment of other applications) place a lower bound on the level and
type of functionality that needs to sit with the application ends (which
may not have to be very much).

Economic efficiency concerns and the imperative of complexity avoidance
further narrow the actual balance of functions (in the abstract). Plus,
the concern for economy of interface between application ends and
intermediary nodes severely limits the scope for having functions
implemented in some cooperative way (see congestion control, two
open-loop systems; routing, almost exclusively in the network; and
fragmentation, completely with the end hosts), discrete parts will thus
fall to either side, and the communication, if any, will be implicit
rather than explicit (see the fate of IP options and ICMP messages).

So far, we still have plenty of scope for functions in the network.
However, once we take minimal coupling, least privilege, cascadability,
and best effort into account, there is actually a fairly low upper bound
on what functions the intermediary network nodes may assume without
collapsing the potential scale of the Internet to trivial proportions.

That sort of summarizes my current gut feeling about the reality of the
Internet (and silently neglects the point that the Internet today is
probably anything but IP connectivity).

> 
> As for best-effort, certainly Alohanet was the epitome of the construct
> and, of course, that predated Alohanet.  (Metcalfe's Ethernet design
> started from a paper he was given, describing Alohanet.)
> 
> 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.)

Matthias

> 
> 
> d/

-- 
Matthias Bärwolff
www.bärwolff.de