[Roll] [roll] Discussion around the design of draft-ietf-roll-nsa-extension based on MRHOF

[Remous-Aris Koutsiamanis <[e-mail]>]

Hello everyone,

We had a discussion today during the ROLL meeting at IETF 118 regarding 
draft-ietf-roll-nsa-extension-12.

After addressing all of Alvaro's and IANA's latest comments, the issue 
of the Objective Function design came up.

Currently, the Common Ancestor Objective Function (CAOF) is "based on" 
MRHOF. "Based on" in the sense that it is described in terms of a diff 
to MRHOF.
The CAOF defines the concept of selecting a secondary "Alternative" 
Parent, in addition to the - primary - Preferred Parent, to be used to 
increase the reliability of the upstream transmissions.
Since the CAOF defines a complete objective function, it must explain 
how the preferred parent selection works. This is the part that is based 
on/inherited from MRHOF.

However, the selection of MRHOF as a base has come into question.

The two reasons given were:
1. We can avoid basing CAOF on MRHOF, and thus make it more generic, by 
simply explaining how the CAOF can modify *any* objective function, 
instead of just MRHOF, to add the ability to select and use an 
alternative parent.
2. According to Pascal Thubert, MRHOF has limited adoption in the 
industry, and thus basing CAOF on MRHOF may limit its adoption.

The counter arguments were:
1. MRHOF is already implemented in an open source operating system 
(Contiki). Proprietary implementations are already opaque and 
non-standardized.
2. The usefulness of rewriting/editing to implement this change is 
questionable.

Does anyone have any feedback or suggestions?

Kind regards,
Aris