[ih] End-to-end - Was: Re: Found the bug - a word to avoid....

[Joseph Touch]

FWIW:

> On Sep 13, 2020, at 1:18 AM, Karl Auerbach via Internet-history <internet-history at elists.isoc.org> wrote:
> 
> If we step back we might see this event as a kind of failure of the end-to-end principle - something in the middle decided to muck with the data moving between the endpoints (in this case the end-points being the members of this mailing list.)

I see a different failure - of the same principle. What happened here is a simple E2E problem - one where posters want to know if mail actually showed up on a list, which includes both being distributed to themselves and others as well as appearing in the archives.

On the one hand, that E2E is the composition of a set of applications into a single service that was never  implemented as E2E at the mail delivery layer. If it were, your mailer would have let you know that you didn’t receive a copy of the mail or that your post didn’t appear in the archive. So, at some level, one E2E failure happened in the design and implementation of ALL mail readers.

However, understanding E2E means knowing what the ends are. The joke about HW/SW is “hardware is that which can be kicked”. The way I taught it at USC, the ends are “that which *I* can kick”, i.e., it’s a statement of relative views of the (recursive, IMO) layers of a network.

So on the other hand, mail list posters can be considered an endpoint. If they had acted as endpoints, the NACK would have resulted in their retrying posts with varying content until they confirm success by receipt and in the archive. I.e., what I did, using the CS 100 method of binary search. Instead, they did something very un-E2E - they sought assistance from the management plane (me) and took issue with the lack of active feedback from various intermediate layers and hops (smtp, postfix, Mailman, etc.).

Over the years, I thought we had learned not to expect active feedback when things fail, for several reasons: security (why ICMPs are blocked), stability (to avoid NACK storms), info theory (you can’t NACK what you didn’t expect), or even the Postel Principle (be liberal in what you [don’t] receive).

So if there’s an observation to make here, it is that E2E failed, but not the way that it might first appear.

Joe (wearing both list admin and contributor hats this time)