Subject: Re: [Roll] Informed move [was: A proposal for Traffic Loop

From: "Anders Jagd" <[email-masked]>
Date: Thu, 15 Oct 2009 13:36:11 -0400

Pascal,

You wrote:

>The draft actually allows moving to a higher rank but there's a catch.
>Whereas a node can reattach right away to obtain a better rank, it needs to
play a little dance that includes detach, wait & see before it can >attach
at a higher rank.

Wouldn't the following statement in 03 deal with exactly that "loop-hole" ?

(From 5.3.2.1. Determination of Eligibility for DIO Processing)
2188  If the rank of SRC as reported in the RA-DIO message is higher
2189  than that of the node within the DAG, and SRC is not a DAG
2190  parent, then the RA-DIO message MUST NOT be considered for
2191  further processing

However, my real question is then whether there are any ideas on how to
enforce such a "MUST NOT" (or even detect a violation) ? Some implementation
may try to differentiate itself by ignoring it. Having a rule that is not
detectable/enforceable seems problematic.

/Anders

---

From: "Pascal Thubert (pthubert)" <[email-masked]>
Date: Fri, 16 Oct 2009 07:30:41 +0200

Hi Anders,

You are correct. I also had a chat with Mukul about that as we work on
the FSM.
There are a number of reasons why the node will have to look at RAs from
below and we need to change that text. 
These might include:

- if the deeper neighbor as a better OCP metrics then remember it for
the next sequence so as not to jump too early too high
- if the deeper neighbor is a parent or a sibling going down, then it
must be eliminated from the list.

The new text will probably be that higher rank is not immediately
selectable. The node has to wait for a new sequence, or detach/reattach
upon a loss of parents. We are still waiting for the results of the poll
but got few answers.

Pascal
>-----Original Message-----
>From: Anders Jagd [mailto:[email-masked]]
>Sent: jeudi 15 octobre 2009 19:36
>To: Pascal Thubert (pthubert)
>Cc: [email-masked]
>Subject: Re: [Roll] Informed move [was: A proposal for Traffic Loop
>
>Pascal,
>
>You wrote:
>
>play a little dance that includes detach, wait & see before it can
>attach
>at a higher rank.
>