Re: [mpls] Update to the bullets on the first page of my review of draft-song-mpls-extension-header-09

[Tony Li <[e-mail]>]

Hi Robert,

> > Each Network Action must specify how it interacts with all other previously defined Network Actions.
> 
> So what happens if such definition is in odds with any previously defined action ? 


One hopefully detects that during the discussion around the action, as part of the RFC development process.

If one has a network action that says “Turn Left at Albuquerque” hopefully we realize that that it conflicts with the action “Turn Right at Albuquerque”.

Note that this does not mean that the two actions could not appear in the same substack. Both are clearly useful, but when found adjacent, would be confusing.  It would be incumbent on the RFC writers to explain the semantics of such an occurrence or to preclude it. 


> How are you going to practically assure that original intention of previously defined action(s) are still maintained ? 


By writing good RFCs and rejected bad ones.


> I am afraid the only option here is to allow complete action independence and leave the sequencing and overlap to the operator to decide how it should be resolved by local ordering or tie breaking. 


One cannot “allow” action independence. You can try to ensure it, by designing actions that are wholly orthogonal, but experience shows that we are imperfect and that our (lack of) understanding will eventually lead us to create actions that will interact. The best that we can do then, is to document the semantics of the interaction. Even then, there are very likely to be unintended consequences (i.e., bugs).

Regards,
Tony