[ih] FTP Design

[Dave Crocker]

On 7/1/2012 7:04 AM, Bernie Cosell wrote:
> What I was mostly grapping with was if
> the protocol were symmetric it could "loop" -- if commands passed each
> other over the net, then the responses passed each other, and those
> kicked off other responses, etc.
...
>  if the commands are will/wont/do/dont and the rules
> follow <THIS> state diagram, then it can't loop and will always end up in
> a reasonable state [just not-looping wasn't enough, of course, lest the
> connection end up with BOTH ends thinking that the other is echoing, or
> vice versa].  Another important idea that it handled was that it was
> extensible: it provided for the notion that one side could ask about
> something unknown and that'd be OK


Timing-insensitivity and tolerance for feature non-support have always 
struck me as core contributions to protocol design.  The first simply 
designs away variable network performance concerns and the latter is 
fundamental to large-scale adoption of new features.

d/
-- 
  Dave Crocker
  Brandenburg InternetWorking
  bbiw.net