Re: DRAFT Montreal minutes - X#NodeArchitecture comments

William Studenmund wrote:
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> On Aug 2, 2006, at 12:15 AM, Sandars, Ken wrote:
> 
>  > Hi David,
>  >
>  > Making an extension key 'Declarative' seems problematic.
>  >
>  > Implementations which do not recognise the key will reply with
>  > X<blah>=NotUnderstood. This may upset the proposer since 
>  > "NotUnderstood"
>  > is unlikely to be an acceptable use of the new key.
>  >
>  > "NotUnderstood" could be treated as a special case, but do we really
>  > want a special case?
> 
> We talked about this in Montreal. Or I tried to a bit.
> 
> At this point, I think we have to accept "NotUnderstood" as a valid 
> response to the key, indicating that the other side doesn't 
> understand. We can't do anything different.
> 
> We thus should state that "NotUnderstood" is an invalid 
> X#NodeArchitecture value (you MUST never attempt to assert that it's 
> your architecture value), and its presence in a response should be 
> taken to mean the responder doesn't understand the key.
> 

Ah, thanks for pointing out that last part.

I think RFC3720 already handles usage of "NotUnderstood" as a
value for any key.  I can add an explicit sentence forbidding
its use as you've stated, but I didn't get that was what was
desired from the final minutes.

Here's the section from 3720, p. 54 I'm referring to:

    The constants "None", "Reject", "Irrelevant", and "NotUnderstood" are
    reserved and MUST ONLY be used as described here.  Violation of this
    rule is a protocol error (in particular the use of "Reject",
    "Irrelevant", and "NotUnderstood" as proposed values).


Here's what the final minutes had:

         - Document behavior of RFC 3720-compliant implementation that
                 receives this new key and does not understand it, and how
                 the other side deals with the resulting response.


Finally, some new proposed text with the explicit forbidding of
"NotUnderstood" (see the last sentence).

    Nodes implementing this key may choose to only transmit the
    key, only log the key values received from other nodes, or both
    transmit and log the key values.  Each node choosing to implement
    transmission of the key values MUST be prepared to handle the
    response of [RFC3720] compliant nodes that do not understand the
    key ([RFC3720] states that compliant nodes MUST respond with
    X#NodeArchitecture=NotUnderstood).  In addition, a node implementing
    transmission MUST NOT transmit "NotUnderstood" as its value,
    as this is a reserved value for all keys [RFC3720].


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