Re: [6tsch] Zero Objective Function discussion

"Pascal Thubert (pthubert)" <pthubert@cisco.com> Tue, 10 September 2013 19:09 UTC

Return-Path: <pthubert@cisco.com>
X-Original-To: 6tsch@ietfa.amsl.com
Delivered-To: 6tsch@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id B252311E81B0 for <6tsch@ietfa.amsl.com>; Tue, 10 Sep 2013 12:09:01 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -10.598
X-Spam-Level:
X-Spam-Status: No, score=-10.598 tagged_above=-999 required=5 tests=[BAYES_00=-2.599, HTML_MESSAGE=0.001, RCVD_IN_DNSWL_HI=-8]
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 74zz-nr6dWZl for <6tsch@ietfa.amsl.com>; Tue, 10 Sep 2013 12:08:56 -0700 (PDT)
Received: from rcdn-iport-3.cisco.com (rcdn-iport-3.cisco.com [173.37.86.74]) by ietfa.amsl.com (Postfix) with ESMTP id 3A3D321F9A61 for <6tsch@ietf.org>; Tue, 10 Sep 2013 12:08:56 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=cisco.com; i=@cisco.com; l=14935; q=dns/txt; s=iport; t=1378840136; x=1380049736; h=from:to:cc:subject:date:message-id:references: in-reply-to:mime-version; bh=vBgUeD6joaFA5+7SJPI2DDCte8GJcquq7ocqn+XSNE8=; b=VMW1i06/fRJLE/ky7fhaoOQjC19eyOL9EJKLhC47WhKYgUBbuUscAk3J cx7kvgtroxyAyTh38cgHGDonwTQ8JXUdDcFqyimc+RkYeIcP1mr2n6SYx jg08HruJu6BmxXTtXFth9f4PgZKl81bZo3qTKKLSfBg7ZJH9aHvaXYM91 I=;
X-IronPort-Anti-Spam-Filtered: true
X-IronPort-Anti-Spam-Result: Au4GAPdsL1KtJXHB/2dsb2JhbABbDoI1RDhRuXyIR4EmFm0HgiUBAQEEHRBFBxACAQgRBAEBCx0HMhQJCAIEDgUIh3oMwkCPKjEGAYMdgQADhUyTWZA8gmE/gio
X-IronPort-AV: E=Sophos; i="4.90,879,1371081600"; d="scan'208,217"; a="258009943"
Received: from rcdn-core2-6.cisco.com ([173.37.113.193]) by rcdn-iport-3.cisco.com with ESMTP; 10 Sep 2013 19:08:55 +0000
Received: from xhc-aln-x10.cisco.com (xhc-aln-x10.cisco.com [173.36.12.84]) by rcdn-core2-6.cisco.com (8.14.5/8.14.5) with ESMTP id r8AJ8tvp030823 (version=TLSv1/SSLv3 cipher=AES128-SHA bits=128 verify=FAIL); Tue, 10 Sep 2013 19:08:55 GMT
Received: from xmb-rcd-x01.cisco.com ([169.254.1.197]) by xhc-aln-x10.cisco.com ([173.36.12.84]) with mapi id 14.02.0318.004; Tue, 10 Sep 2013 14:08:54 -0500
From: "Pascal Thubert (pthubert)" <pthubert@cisco.com>
To: "xvilajosana@eecs.berkeley.edu" <xvilajosana@eecs.berkeley.edu>
Thread-Topic: [6tsch] Zero Objective Function discussion
Thread-Index: AQHOrk6Gtb6ROlh65EK+zZJeGKtxe5m/RIaA
Date: Tue, 10 Sep 2013 19:08:53 +0000
Deferred-Delivery: Tue, 10 Sep 2013 19:08:00 +0000
Message-ID: <E045AECD98228444A58C61C200AE1BD8414615AE@xmb-rcd-x01.cisco.com>
References: <CADJ9OA8vNGCmy-2X901pqnmZuSCQ1d=GPeHPE=SD25JJkfwGgw@mail.gmail.com> <E045AECD98228444A58C61C200AE1BD84145CF1E@xmb-rcd-x01.cisco.com> <CALEMV4aaQgqB9q7ht5XeySmhUOWUHtu2x9phkw3N=r3xqt5Rvg@mail.gmail.com>
In-Reply-To: <CALEMV4aaQgqB9q7ht5XeySmhUOWUHtu2x9phkw3N=r3xqt5Rvg@mail.gmail.com>
Accept-Language: fr-FR, en-US
Content-Language: en-US
X-MS-Has-Attach:
X-MS-TNEF-Correlator:
x-originating-ip: [10.61.85.35]
Content-Type: multipart/alternative; boundary="_000_E045AECD98228444A58C61C200AE1BD8414615AExmbrcdx01ciscoc_"
MIME-Version: 1.0
Cc: Thomas Watteyne <watteyne@eecs.berkeley.edu>, 6TSCH <6tsch@ietf.org>
Subject: Re: [6tsch] Zero Objective Function discussion
X-BeenThere: 6tsch@ietf.org
X-Mailman-Version: 2.1.12
Precedence: list
List-Id: "Discuss link layer model for Deterministic IPv6 over the TSCH mode of IEEE 802.15.4e, and impacts on RPL and 6LoWPAN such as resource allocation" <6tsch.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/6tsch>, <mailto:6tsch-request@ietf.org?subject=unsubscribe>
List-Archive: <http://www.ietf.org/mail-archive/web/6tsch>
List-Post: <mailto:6tsch@ietf.org>
List-Help: <mailto:6tsch-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/6tsch>, <mailto:6tsch-request@ietf.org?subject=subscribe>
X-List-Received-Date: Tue, 10 Sep 2013 19:09:01 -0000

Hello Xavi:

Great!

I'd add the following:


RFC 6550    3.5.1<http://tools.ietf.org/html/rfc6550#section-3.5.1>.1>. Rank Comparison (DAGRank())has:
"

When an Objective Function computes Rank, the Objective Function

   operates on the entire (i.e., 16-bit) Rank quantity.  When Rank is

   compared, e.g., for determination of parent relationships or loop

   detection, the integer portion of the Rank is to be used.  The

   integer portion of the Rank is computed by the DAGRank() macro as

   follows, where floor(x) is the function that evaluates to the

   greatest integer less than or equal to x:



              DAGRank(rank) = floor(rank/MinHopRankIncrease)



   For example, if a 16-bit Rank quantity is decimal 27, and the

   MinHopRankIncrease is decimal 16, then DAGRank(27) = floor(1.6875) =

   1.  The integer part of the Rank is 1 and the fractional part is

   11/16.

"
DAGRank(rank) is what we expect to place in the Flow label and the join priority.
In our case:

r(1)=r(0)+rank_increase = 0+683               => DAGRank(rank) = 2
r(2)=r(1)+683=1366                                         => DAGRank(rank) = 5
r(3)=r(2)+683=2049                                         => DAGRank(rank) = 8
r(4)=r(3)+683=2732                                         => DAGRank(rank) = 10
r(5)=r(4)+683=3415                                         => DAGRank(rank) = 13

We see that the DAGRank() always increases at least by one. This is the desired property so as to ensure that we can detect loop with just one octet in the flow label.
Note that the real 2 octets Rank does not lose the rounding info since the DIP always passes 2 octets.

Cheers,

Pascal

From: Xavier Vilajosana Guillen [mailto:xvilajosana@eecs.berkeley.edu]
Sent: mardi 10 septembre 2013 19:53
To: Pascal Thubert (pthubert)
Cc: Thomas Watteyne; 6TSCH
Subject: Re: [6tsch] Zero Objective Function discussion

Hi all,

after some study I agree that we can use the RFC6552 in the minimal 6TiSCH configuration. I would like to call for approval or more input from others before I consolidate the text in the draft.

I put here an example following Pascal suggestion:

Given

Rf = 1
Sp = 2* ETX
Sr = 0
minHopRankIncrease = 256 (default in RPL)
ETX=(xmit/ack)

r(n) = r(p) + rank_increase
rank_increase= (Rf*Sp + Sr) * minHopRankIncrease
rank_increase=(512*xmit/ack)


if we take 5 hops (95 are supported) network and r(0)=0 and xmit=100 and ack=75 for all nodes

r(1)=r(0)+rank_increase = 0+683 with f=0
r(2)=r(1)+683=1366 with f=1
r(3)=r(2)+683=2049 with f=2
r(4)=r(3)+683=2732 with f=2
r(5)=r(4)+683=3415 with f=3
...
etc...

so f is monotonically increasing and the rank function enables more than enough hops.
Please provide feedback.
cheers!
Xavi