I certainly favor the simplicity of
Option 1 over Option 2; however last week we also had an Option 3 which
was my favorite - that being that the node simply does not join the DAG.
Option 1 as described, indicates that the node joins the DAG as a
leaf node. My question is - how does a node even know it's a leaf
node? My understanding is that DAG children know their parents, but
DAG parents do not know who their children are or even if they have children.
If there is a way to know that a node is a leaf node, then what does
it do to maintain its status of a leaf node; that is not allowing other
nodes to attach to it in the future as children?
If someone can help me understand these
mechanics, I will change my vote.
Thanks,
Jerry
JP Vasseur <jvasseur at cisco.com> Sent by: roll-bounces at ietf.org
11/05/2009 03:17 AM
To
roll WG <roll at ietf.org>
cc
Subject
[Roll] Opinion please
Dear all,
/co-chair hat off/
We would welcome your opinion on the following issue:
Suppose that a DAG is formed that support OFx. A new node willing to
join the DAG does not support OFx but OFy. Note that by OF we actually
mean the Objective function and the metric.
We have two options here.
Option 1: The node simply joins the DAG as a leaf. In order words, the
node has connectivity since it joins the DAG but will not act as a
router for others since it does not understand the OF. Parent
selection could be a simply a "random".
Option 2: The node joins the DAG and falls back to the "default"
OCP.
From there is prolongs the DAG but with OF0 (of course inconsistent
metrics are not added). This also means that everynode MUST implement
OF0 and that the network may compromise nodes with different OF at
some point. Several options even more complex have been discussed
where one could use common denominator to get as close as possible to
the desired OF, allow a node not to be so "altruistic", ...
My personal view is that OF management can quick get fairly complex
and hard to manage. Option 1 is extremely simple and easy to manage.
If a node is mis-configured (does not support the OF of the DAG) it
can join it as a leaf in order to have connectivity and send an alarm
to fix its configuration. We now just need to specify OF in some
document and this is it.
Several of you mentioned that they were leaning toward option 1, but
could you please express your opinion, we would like to have it solved
for the next revision next week.
Thanks.
JP.
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