RE: Protocol Definition

X.200 - ITU's version of the OSI model - defines an "association" as peering at any layer of the OSI stack.
Thus an association at layer 3 is a pair of IP addresses, while an association at layer 4 is a pair of socket IDs.
If the association is requested then it becomes a "connection".
A "session" is an association at layer 5.

A process in computation is defined as an entity that is independent 
in the sense that it can request and own resources (e.g., CPU time and memory).
Many processes can exist side by side, and can even communicate via IPC,
but processes do not have a hierarchy such as we have in communications.
The closest thing is the fact that processes can own tasks or threads as sub-entities
(tasks are not indendent - their memory and CPU time are taken from their father process).

Just as an association runs protocols at different layers, a single process frequently runs multiple algorithms.
But these algorithms are usually not layered.

A protocol between two entities often involves algorithms on both sides,
but an association does not necessarily link two processes on the communicating sides.

Y(J)S

-----Original Message-----
From: ietf-bounces@ietf.org [mailto:ietf-bounces@ietf.org] On Behalf Of Dave CROCKER
Sent: Friday, January 06, 2012 05:03
To: Dave Cridland
Cc: IETF-Discussion
Subject: Re: Protocol Definition

On 1/5/2012 1:41 PM, Dave Cridland wrote:
> Association, to my mind, means a transport layer connection, hence it's usage in
> SNMP and other OSI-related things.
>
> Session isn't much less damaged, as a term, I admit, but it is in common usage.
> And like algorithms, and protocols, you can open up a session to find other
> sessions inside.

Actually, my recollection is that 'association' was an application-level 
construct from OSI.

But I came to the same conclusion as you:  "session" is an established term in 
IETF parlance and has the basic reality of describing a protocol in operation 
between two (or more?) hosts/endsystems/endpoints/...

Does this resonate with others?

d/
-- 

   Dave Crocker
   Brandenburg InternetWorking
   bbiw.net
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