[ih] IEN's as txt

[dhc2 at dcrocker.net (Dave Crocker)]

On 2/10/2017 3:31 PM, Joe Touch wrote:
> A protocol consists of a FSM specification:
>     - those messages that are exchanged (sent or received) "on the wire"
>     - state
>     - events sent/received to the next layer up
>     - time events
>     - the relationship between the above events and states (a transition
> table)


Actually, the constraint to the comms channel perspective has 
historically been extremely helpful in getting people to focus on 
machine-independent interoperability rather than to fall back on 
defining things in terms of APIs, as has become increasingly common.

Issues of 'state' derive from the rules about what PDUs are allowed when 
and what they must/may contain.

However the point about provider and consumer interfaces -- that is, 
interacting with the layers below and aove -- for an engine implementing 
the protocol is a different matter and frequently gets inadequate 
attention.  The concept of protocol 'payload' often provides helpful 
assistance in getting folk to distinguish between information that is 
'within' the protocol mechanism versus information that is external to it.

d/

-- 

   Dave Crocker
   Brandenburg InternetWorking
   bbiw.net