Re: [Roll] enrollment priority

Michael Richardson <> Fri, 10 April 2020 21:44 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id D1ABE3A0DFC for <>; Fri, 10 Apr 2020 14:44:18 -0700 (PDT)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -1.888
X-Spam-Status: No, score=-1.888 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, SPF_HELO_NONE=0.001, T_SPF_PERMERROR=0.01, URIBL_BLOCKED=0.001] autolearn=ham autolearn_force=no
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id Aw6wMBLM0WML for <>; Fri, 10 Apr 2020 14:44:17 -0700 (PDT)
Received: from ( [IPv6:2607:f0b0:f:3:216:3eff:fe7c:d1f3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by (Postfix) with ESMTPS id 8D4143A0DFA for <>; Fri, 10 Apr 2020 14:44:16 -0700 (PDT)
Received: from ( []) by (Postfix) with ESMTP id F026F3897D for <>; Fri, 10 Apr 2020 17:42:33 -0400 (EDT)
Received: from localhost (localhost [IPv6:::1]) by (Postfix) with ESMTP id C990710ED for <>; Fri, 10 Apr 2020 17:44:11 -0400 (EDT)
From: Michael Richardson <>
To: Routing Over Low power and Lossy networks <>
In-Reply-To: <>
References: <>
X-Mailer: MH-E 8.6; nmh 1.7+dev; GNU Emacs 25.1.1
X-Face: $\n1pF)h^`}$H>Hk{L"x@)JS7<%Az}5RyS@k9X%29-lHB$Ti.V>2bi.~ehC0; <'$9xN5Ub# z!G,p`nR&p7Fz@^UXIn156S8.~^@MJ*mMsD7=QFeq%AL4m<nPbLgmtKK-5dC@#:k
MIME-Version: 1.0
Content-Type: multipart/signed; boundary="=-=-="; micalg="pgp-sha256"; protocol="application/pgp-signature"
Date: Fri, 10 Apr 2020 17:44:11 -0400
Message-ID: <8722.1586555051@localhost>
Archived-At: <>
Subject: Re: [Roll] enrollment priority
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Routing Over Low power and Lossy networks <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Fri, 10 Apr 2020 21:44:19 -0000

Rahul Jadhav <> wrote:
    > The draft should make it clear that the min-priority can only be
    > reduced or kept the same (i.e., the min-priority absolute value can
    > only increase, thus reducing priority) going downstream in the
    > sub-DODAG. For e.g., if a 6LR sets the min-priority to 10, the
    > downstream 6LRs can only set the value >= 10 in their min-priority.

I will add, to section 2:

    > Consider the following scenario (the attached image will help explain):
    > Node C's preferred parent is node B and alt parent is node A. What
    > happens if the min-priority of node B changes to 127 after the node C
    > has joined the network with B as a preferred parent? I am assuming
    > that the min-priority impacts only the newly joining nodes i.e., once
    > node B changes the priority to 127 then node C also changes the
    > priority to 127 and thus no new nodes join. However, the change in
    > node B's min-priority may not impact node C's decision to continue
    > using node B as the preferred parent (?). What happens when node C has
    > alternate parent node A whose priority is lesser than 127. Should node
    > C switch to node A so as to allow new downstream nodes to join the
    > network?

First, I think that if node C had a MP of 127, then it would *NOT* advertise
itself as a Join Proxy.  So if it was sending Enhanced Beacons, then it
  a) set proxy prio to 0x7f.
  b) maybe even stop sending EBs [have to think about this]
  c) not accept any unencrypted traffic!

so yeah, node D would be out of luck.

If node C *does* change to node A, then it would change it's priority.
But it has to do that, and maybe there are reasons why A won't accept it.

    > I don't believe there would be backward compatibility issues with this
    > new option, but the draft can clarify this explicitly.

I have added:

  This document uses the extensions mechanism designed into {{!RFC6550}}.
  It does not need any mechanism to enable it.

  6LRs that support this option, but whose parent does not send it SHOULD
  assume a value of 0x40 as their base value.
  The nodes adjust this base value based upon their observed congestion,
  emitting their adjusted DIO value to their children.

(0x40 is my wet-finger-in-the-air, seat-of-the-pants guess)

    > We tried working on a problem-statement in the past in LWIG [1] which
    > talked about how to handle the case where some upstream nodes cache
    > (routing/neighbor) is full and how would it stop the new downstream
    > nodes to attach in that path. Enrollment priority was referenced as a
    > possible solution.

Good.  Would more informative cross-references help?
Do you want to co-author?

]               Never tell me the odds!                 | ipv6 mesh networks [
]   Michael Richardson, Sandelman Software Works        |    IoT architect   [
]        |   ruby on rails    [

Michael Richardson <>, Sandelman Software Works
 -= IPv6 IoT consulting =-