Re: [Roll] knowing which multiple metrics matter: MRHOF related questions

Mukul Goyal <mukul@uwm.edu> Tue, 05 June 2012 08:55 UTC

Return-Path: <prvs=496b680bf=mukul@uwm.edu>
X-Original-To: roll@ietfa.amsl.com
Delivered-To: roll@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id C6F5921F86BE for <roll@ietfa.amsl.com>; Tue, 5 Jun 2012 01:55:38 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -6.465
X-Spam-Level:
X-Spam-Status: No, score=-6.465 tagged_above=-999 required=5 tests=[AWL=0.134, BAYES_00=-2.599, RCVD_IN_DNSWL_MED=-4]
Received: from mail.ietf.org ([12.22.58.30]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 3iXj7WEH5lAp for <roll@ietfa.amsl.com>; Tue, 5 Jun 2012 01:55:38 -0700 (PDT)
Received: from ip2mta.uwm.edu (ip2mta.uwm.edu [129.89.7.20]) by ietfa.amsl.com (Postfix) with ESMTP id E603721F865F for <roll@ietf.org>; Tue, 5 Jun 2012 01:55:37 -0700 (PDT)
X-IronPort-Anti-Spam-Filtered: true
X-IronPort-Anti-Spam-Result: Ap4EAH3IzU9/AAAB/2dsb2JhbABFhU6yAwEBAQQBAQEgSwsMDw4DBAEBAwINGQIpKAgGE4gLC6Q3iWWJBIEjiXCEfoESA4hAjFuBD45ngn4
Received: from localhost (localhost.localdomain [127.0.0.1]) by mta02.pantherlink.uwm.edu (Postfix) with ESMTP id 65B2112E3BA; Tue, 5 Jun 2012 03:55:37 -0500 (CDT)
X-Virus-Scanned: amavisd-new at mta02.pantherlink.uwm.edu
Received: from mta02.pantherlink.uwm.edu ([127.0.0.1]) by localhost (mta02.pantherlink.uwm.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id dHc3MTYStPAO; Tue, 5 Jun 2012 03:55:36 -0500 (CDT)
Received: from mail17.pantherlink.uwm.edu (mail17.pantherlink.uwm.edu [129.89.7.177]) by mta02.pantherlink.uwm.edu (Postfix) with ESMTP id F03FD12E3AE; Tue, 5 Jun 2012 03:55:36 -0500 (CDT)
Date: Tue, 5 Jun 2012 03:55:36 -0500 (CDT)
From: Mukul Goyal <mukul@uwm.edu>
To: Ralph Droms <rdroms.ietf@gmail.com>
Message-ID: <1064008108.595562.1338886536842.JavaMail.root@mail17.pantherlink.uwm.edu>
In-Reply-To: <599545E1-7B6A-4649-97F7-E28107C3ECF2@gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit
X-Originating-IP: [99.20.249.193]
X-Mailer: Zimbra 6.0.15_GA_2995 (ZimbraWebClient - IE8 (Win)/6.0.15_GA_2995)
X-Authenticated-User: mukul@uwm.edu
Cc: roll <roll@ietf.org>, Stiemerling Martin <mstiemerling@googlemail.com>, Haberman Brian <brian@innovationslab.net>
Subject: Re: [Roll] knowing which multiple metrics matter: MRHOF related questions
X-BeenThere: roll@ietf.org
X-Mailman-Version: 2.1.12
Precedence: list
List-Id: Routing Over Low power and Lossy networks <roll.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/roll>, <mailto:roll-request@ietf.org?subject=unsubscribe>
List-Archive: <http://www.ietf.org/mail-archive/web/roll>
List-Post: <mailto:roll@ietf.org>
List-Help: <mailto:roll-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/roll>, <mailto:roll-request@ietf.org?subject=subscribe>
X-List-Received-Date: Tue, 05 Jun 2012 08:55:39 -0000

Hi Ralph

*****************************************************************************
[MCR]
> - do the nodes of a DODAG have to use the same metrics to pick a parent,
>  (and if so, how do they agree)
>  I think that they do not, so long as they use an algorithm (such as
>  MRHOF) which has certain properties.
> 

[Mukul]
Yes, the nodes in a DODAG have to use the same metrics. Otherwise, it is not possible for an OF to map the aggregated (from root till this node) values of the metrics to a rank.

[Ralph2]
"metrics" or "metric"?

[Mukul2]
"Metrics" if we are talking about OF in general. "Metric" if we are talking about MRHOF in particular.

[Ralph2]
  Can different nodes use different metrics in a RPL instance that specifies MRHOF?  I would think the answer is "no"; i.e., all nodes in a RPL instance MUST use the same metric as the "selected metric".

[Mukul2]
You are right.

**********************************************************************************

[MCR] 
> - if we had multiple RPL instances in an LLN, using different metrics,
>  then we would have multiple RPL Instances and DODAGs.  The different
>  set of metrics would not co-exist in the same RPL Instance.

[Mukul]
> Not sure what does the first sentence mean. About the second, different sets of metrics can certainly coexist in the same RPL instance. An RPL Instance is associated with a particular OF but different DODAGs in the RPL Instance can certainly use different routing metrics.

[Ralph2]
Perhaps I am confused.  Do all the nodes in a single DODAG use the same metric while nodes in different DODAGs (in the same RPL instance) can use different metrics?  I.e., for a RPL instance with tow DODAGs, all the nodes in DODAG1 use ETX while all the nodes in DODAG2 use hop count?

[Mukul2]
I thought so until Pascal told me today that this is not correct. The reason is that a node may want to jump from one DAG to another (e.g. if both DAGs provide connectivity to a particular prefix and the node will have a better rank in the other DAG). But, in order to allow a node to compare its rank in different DAGs, both OF and metrics in use should be same for both DAGs.

Thanks
Mukul


> 
> ----- Original Message -----
> From: "Michael Richardson" <mcr+ietf@sandelman.ca>
> To: "Pascal Thubert (pthubert)" <pthubert@cisco.com>
> Cc: roll@ietf.org
> Sent: Friday, May 25, 2012 2:29:49 PM
> Subject: Re: [Roll] knowing which multiple metrics matter: MRHOF related	questions
> 
> 
>>>>>> "Pascal" == Pascal Thubert <(pthubert)" <pthubert@cisco.com>> writes:
>    Pascal> I think RPL does not want to take party there. The OF is a
>    Pascal> piece of logic to tie metrics and policies together.  
> 
> My question is:
> 
> - do the nodes of a DODAG have to use the same metrics to pick a parent,
>  (and if so, how do they agree)
>  I think that they do not, so long as they use an algorithm (such as
>  MRHOF) which has certain properties.
> 
> - if we had multiple RPL instances in an LLN, using different metrics,
>  then we would have multiple RPL Instances and DODAGs.  The different
>  set of metrics would not co-exist in the same RPL Instance.
> 
> 
> -- 
> Michael Richardson <mcr+IETF@sandelman.ca>ca>, Sandelman Software Works 
> IETF ROLL WG co-chair.    http://datatracker.ietf.org/wg/roll/charter/
> 
> 
> _______________________________________________
> Roll mailing list
> Roll@ietf.org
> https://www.ietf.org/mailman/listinfo/roll
> _______________________________________________
> Roll mailing list
> Roll@ietf.org
> https://www.ietf.org/mailman/listinfo/roll