Subject: Re: The rights of email senders and IETF rough consensus

From: Bob Braden <[email-masked]>
Date: Tue, 20 Dec 2005 11:06:37 -0800 (PST)

clean
  *> 
  *> Dave Crocker wrote:
  *> >> IETF should not make it more difficult for the Internet to adapt to
  *> >> changing conditions by standardizing protocols that only work in a
  *> >> narrow set of conditions - even when those conditions are reflected
  *> >> in some providers' current contracts or policies.
  *> > 
  *> > 
  *> > Like ARP?
  *> 
  *> I wasn't around when the ARP decision was made, so I don't know how
  *> widely it was realized at the time that the approach was shortsighted. 
  *> we cannot, of course, have perfect foresight, so it will always be 
  *> possible to find examples of poor decisions made long ago.  however the 
  *> lack of perfect foresight doesn't mean we should make our present 
  *> decisions blindly.

This is a strange discussion.  Broadcast networks are an important
class of link layer technologies, and I would say that by any measure
ARP was a huge technical success.  It may well have been responsible
for the great popularity of Ethernet and its followons.  ARP also
established an important architectural technique.  I don't understand
the suggestion that it was "shortsighted".

Bob Braden

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From: Keith Moore <[email-masked]>
Date: Tue, 20 Dec 2005 14:41:49 -0500

> the suggestion that it was "shortsighted".

This was probably a poor choice of words on my part.  One can claim that 
ARP was shortsighted just like one can claim that IPv4's 32-bit address 
was shortsighted, or the coupling between TCP's endpoint identifers and 
the addresses in the IP header (lack of endpoint/locator separation) was 
shortsighted.  It's easy to make such claims in hindsight, when a 
protocol has become so successful that the very scale in which it is 
used makes any of its design compromises painful.  Sometimes a 
compromise that was crucial to the success of the design eventually 
becomes painful precisely because it was a good compromise at the time.

At any rate, my intent in the earlier message was to concede (what I 
took to be) Dave's point about ARP being overall a good thing despite 
its limitations, without revisiting the merits of whether ARP should or 
should not have been adopted.  From my understanding of the 
circumstances at the time ARP looks like a reasonable design choice even 
if some of its limitations are now apparent. But I don't see the ARP 
situation as being similar enough to the SPF situation to be instructive 
for the latter.

Keith