Skip to main content

Use of the IPv6 Flow Label within an LLN
draft-thubert-roll-flow-label-00

The information below is for an old version of the document.
Document Type
This is an older version of an Internet-Draft whose latest revision state is "Expired".
Author Pascal Thubert
Last updated 2012-05-04
RFC stream (None)
Formats
Stream Stream state (No stream defined)
Consensus boilerplate Unknown
RFC Editor Note (None)
IESG IESG state I-D Exists
Telechat date (None)
Responsible AD (None)
Send notices to (None)
draft-thubert-roll-flow-label-00
ROLL                                                     P. Thubert, Ed.
Internet-Draft                                                     Cisco
Intended status: Standards Track                             May 4, 2012
Expires: November 5, 2012

                Use of the IPv6 Flow Label within an LLN
                    draft-thubert-roll-flow-label-00

Abstract

   In a Low Power Lossy Network, the traditional tuple of source,
   destination and ports might not be the proper indication to isolate a
   meaningful flow.  For instance, it can be a requirement for the
   aggregation of related measurements from multiple sources to be
   treated as a single flow following a same path in order to experience
   similar jitter and latency.  In that case, the Flow Label in packets
   outgoing a RPL domain could and sometimes should be set by the root
   of the RPL structure.  It derives that the Flow Label could be reused
   inside the RPL domain.  This document present how the Flow Label can
   be used inside a LLN as a replacement to the RPL option and provides
   rules for the root to set and reset the Flow Label when forwarding
   between the inside of RPL domain and the larger Internet, in both
   direction.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on November 5, 2012.

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal

Thubert                 Expires November 5, 2012                [Page 1]
Internet-Draft  Use of the IPv6 Flow Label within an LLN        May 2012

   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 4
   3.  Flow Label Format Within the RPL Domain . . . . . . . . . . . . 4
   4.  Root Operation  . . . . . . . . . . . . . . . . . . . . . . . . 5
     4.1.  Incoming Packets  . . . . . . . . . . . . . . . . . . . . . 5
     4.2.  Outgoing Packets  . . . . . . . . . . . . . . . . . . . . . 5
   5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 6
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 6
     8.1.  Normative References  . . . . . . . . . . . . . . . . . . . 6
     8.2.  Informative References  . . . . . . . . . . . . . . . . . . 6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 6

Thubert                 Expires November 5, 2012                [Page 2]
Internet-Draft  Use of the IPv6 Flow Label within an LLN        May 2012

1.  Introduction

   In some Low Power and Lossy Network (LLN) applications such as
   control systems [RFC5673], a packet loss is usually acceptable but
   jitter and latency must be strictly controlled as they can play a
   critical role in the interpretation of the measured information.
   Sensory systems are often distributed, and the control information
   can in fact be aggregated from multiple source.

   If this aggregated control information is transported across the
   Internet, it should be treated as a single flow for two reasons:

      The bulk of the traffic consists of small chunks of data (in the
      order few bytes to a few tens of bytes) at a time.  In industrial
      applications, a typical frequency is 4Hz but it can be a lot
      slower than that for, say, environmental monitoring.  The
      granularity of that traffic is too small to make a lot of sense in
      load balancing application.

      The control system may be fooled into misbehaviors if the latency
      and jitter of packets vary from a source to another source for a
      related measurement.

   This is a case where related packets from multiple sources should not
   be load-balanced along their path in the Internet; this is
   discouraged by tagging those packets with a same Flow Label in the
   IPv6 [RFC2460] header.

   The Routing Protocol for Low Power and Lossy Networks (RPL) [RFC6550]
   specification defines a generic Distance Vector protocol that is
   adapted to a variety of LLNs.  RPL forms Destination Oriented
   Directed Acyclic Graphs (DODAGs) which root often acts as the Border
   Router to connect the RPL domain to the Internet.  The root is
   responsible to select the RPL Instance that is used to forward a
   packet coming from the Internet into the RPL domain.

   A classical RPL implementation will use the RPL Option for Carrying
   RPL Information in Data-Plane Datagrams [RFC6553] to tag a packet
   with the Instance ID and other information that RPL requires for its
   operation within the RPL domain.  Sadly, the Option must be placed in
   a Hop-by-Hop option that must be inserted or removed as the packet
   crosses the border of the RPL domain.  This operation may involve an
   extra encapsulation that is detrimental to the network operation, in
   particular with regards to bandwidth and battery constraints.

   All the packets that are leaving a DODAG of a RPL domain towards the
   Internet will transit via a same root.  The root is an ideal place to
   set the IPv6 Flow Label to a same value across multiple sources of a

Thubert                 Expires November 5, 2012                [Page 3]
Internet-Draft  Use of the IPv6 Flow Label within an LLN        May 2012

   same flow when that operation is needed, ensuring complience with the
   rules defined by the IPv6 Flow Label Specification [RFC6437] within
   the Internet.  At the same time, the root segragates the Internet and
   the RPL domain, allowing to reuse the Flow Label within the RPL
   domain.

   This document specifies how the Flow Label can be reused within the
   RPL domain as a replacement to the RPL option.  The use of the Flow
   Label within a RPL domain is an instance of the stateful scenarios
   decribed in [RFC6437] where the states include the rank of a node and
   the RPLInstanceID that identifies the routing topology.

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

   The Terminology used in this document is consistent with and
   incorporates that described in `Terminology in Low power And Lossy
   Networks' [I-D.ietf-roll-terminology] and [RFC6550].

3.  Flow Label Format Within the RPL Domain

   [RFC6550] section 11.2 specifies the fields that are to be placed
   into the packets for the purpose of Instance Identification, as well
   as Loop Avoidance and Detection.  Those fields include an 'O', and
   'R' and an 'F' bits, the 8-bit RPLInstanceID, and the 16-bit
   SenderRank.  SenderRank is the result of the DAGRank operation on the
   rank of the sender, where the DAGRank operation is defined in section
   3.5.1 as:

      DAGRank(rank) = floor(rank/MinHopRankIncrease)

   If MinHopRankIncrease is set to a multiple of 256, it appears that
   the most significant 8 bits of the SenderRank will be all zeroes and
   could be ommitted.  In that case, the Flow Label MAY be used as a
   replacement to the [RFC6553] RPL option.  To achive this, the
   SenderRank is expressed with 8 least significant bits, and the
   information carried within the Flow Label in a packet is constructed
   follows:

Thubert                 Expires November 5, 2012                [Page 4]
Internet-Draft  Use of the IPv6 Flow Label within an LLN        May 2012

           0                   1                   2
           0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                  | |O|R|F|  SenderRank   | RPLInstanceID |
                  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                       Figure 1: The RPL Flow Label

   The first (leftmost) bit of the Flow Label is reserved and should be
   set to zero.

4.  Root Operation

4.1.  Incoming Packets

   When routing a packet towards the RPL domain, the root applies a
   policy to determine whether the Flow Label is to be used to carry the
   RPL information.  If so, the root MUST reset the Flow Label and then
   it MUST set all the fields in the Flow Label as prescribed by
   [RFC6553] using the format specified in Figure 1.  In particular, the
   root selects the Instance that will be used to forward the packet
   within the RPL domain.

4.2.  Outgoing Packets

   When routing a packet outside the RPL domain, the root applies a
   policy to determine whether the Flow Label was used to carry the RPL
   information.  If so, the root MUST reset the Flow Label.  The root
   SHOULD recompute a Flow Label following the rules prescribed by
   [RFC6553].  In particular, the root MAY ignore the source address but
   it SHOULD use the RPLInstanceID for the computation.

5.  Security Considerations

   The process of using the Flow Label as opposed to the RPL option does
   not appear to create any opening for new threat compared to
   [RFC6553].

6.  IANA Considerations

   No IANA action is required for this specification.

Thubert                 Expires November 5, 2012                [Page 5]
Internet-Draft  Use of the IPv6 Flow Label within an LLN        May 2012

7.  Acknowledgments

8.  References

8.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2460]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 2460, December 1998.

   [RFC6550]  Winter, T., Thubert, P., Brandt, A., Hui, J., Kelsey, R.,
              Levis, P., Pister, K., Struik, R., Vasseur, JP., and R.
              Alexander, "RPL: IPv6 Routing Protocol for Low-Power and
              Lossy Networks", RFC 6550, March 2012.

   [RFC6553]  Hui, J. and JP. Vasseur, "The Routing Protocol for Low-
              Power and Lossy Networks (RPL) Option for Carrying RPL
              Information in Data-Plane Datagrams", RFC 6553,
              March 2012.

8.2.  Informative References

   [I-D.ietf-roll-terminology]
              Vasseur, J., "Terminology in Low power And Lossy
              Networks", draft-ietf-roll-terminology-06 (work in
              progress), September 2011.

   [RFC5673]  Pister, K., Thubert, P., Dwars, S., and T. Phinney,
              "Industrial Routing Requirements in Low-Power and Lossy
              Networks", RFC 5673, October 2009.

   [RFC6437]  Amante, S., Carpenter, B., Jiang, S., and J. Rajahalme,
              "IPv6 Flow Label Specification", RFC 6437, November 2011.

Thubert                 Expires November 5, 2012                [Page 6]
Internet-Draft  Use of the IPv6 Flow Label within an LLN        May 2012

Author's Address

   Pascal Thubert (editor)
   Cisco Systems
   Village d'Entreprises Green Side
   400, Avenue de Roumanille
   Batiment T3
   Biot - Sophia Antipolis  06410
   FRANCE

   Phone: +33 4 97 23 26 34
   Email: pthubert@cisco.com

Thubert                 Expires November 5, 2012                [Page 7]