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Versions: 00 01 02 03 04 05 RFC 8025

6lo                                                      P. Thubert, Ed.
Internet-Draft                                                     Cisco
Updates: 4944 (if approved)                             January 14, 2016
Intended status: Standards Track
Expires: July 17, 2016


                        6LoWPAN Paging Dispatch
                   draft-ietf-6lo-paging-dispatch-00

Abstract

   This specification introduces a new context switch mechanism for
   6LoWPAN compression, expressed in terms of Pages and signaled by a
   new Paging Dispatch.

Status of This Memo

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

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   This Internet-Draft will expire on July 17, 2016.

Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  Updating RFC 4944 . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Page 1 Paging Dispatch  . . . . . . . . . . . . . . . . . . .   4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   5
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   The design of Low Power and Lossy Networks (LLNs) is generally
   focused on saving energy, a very constrained resource in most cases.
   The other constraints, such as the memory capacity and the duty
   cycling of the LLN devices, derive from that primary concern.  Energy
   is often available from primary batteries that are expected to last
   for years, or is scavenged from the environment in very limited
   quantities.  Any protocol that is intended for use in LLNs must be
   designed with the primary concern of saving energy as a strict
   requirement.

   Controlling the amount of data transmission is one possible venue to
   save energy.  In a number of LLN standards, the frame size is limited
   to much smaller values than the IPv6 maximum transmission unit (MTU)
   of 1280 bytes.  In particular, an LLN that relies on the classical
   Physical Layer (PHY) of IEEE 802.15.4 [IEEE802154] is limited to 127
   bytes per frame.  The need to compress IPv6 packets over IEEE
   802.15.4 led to the 6LoWPAN Header Compression [RFC6282] work
   (6LoWPAN-HC).

   As more and more protocols need to be compressed, the encoding
   capabilities of the original dispatch defined in the 6lo adaptation
   layer framework ([RFC4944],[RFC6282]) becomes saturated.  This
   specification introduces a new context switch mechanism for 6LoWPAN
   compression, expressed in terms of Pages and signaled by a new Paging
   Dispatch.

2.  Terminology

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



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   The Terminology used in this document is consistent with and
   incorporates that described in `Terminology in Low power And Lossy
   Networks' [RFC7102] and [RFC7228].

3.  Updating RFC 4944

   This draft adapts 6LoWPAN while maintaining backward compatibility
   with IPv6 over IEEE 802.15.4 [RFC4944] by introducing a concept of
   "context" in the 6LoWPAN parser, a context being identified by a Page
   number.  This specification defines 16 Pages.

   Pages are delimited in a 6LoWPAN packet by a Paging Dispatch value
   that indicates the next current Page.  The Page number is encoded in
   a Paging Dispatch with the Value Bit Pattern of 1111xxxx where xxxx
   is the Page number, 0 to 15, as described in Figure 1:

                            0
                            0 1 2 3 4 5 6 7
                           +-+-+-+-+-+-+-+-+
                           |1|1|1|1|Page Nb|
                           +-+-+-+-+-+-+-+-+

           Figure 1: Paging Dispatch with Page Number Encoding.

   Values of the Dispatch byte defined in [RFC4944] are considered as
   belonging to the Page 0 parsing context, which is the default and
   does not need to be signaled explicitly at the beginning of a 6LoWPAN
   packet.  This ensures backward compatibility with existing
   implementations of 6LoWPAN.

   Note: This specification does not use the Escape Dispatch, which
   extends Page 0 to more values, but rather allocates another Dispatch
   Bit Pattern (1111xxxx) for a new Paging Dispatch, that is present in
   all Pages, including Page 0 and Pages defined in future
   specifications, to indicate the next parsing context represented by
   its Page number.  The rationale for avoiding that approach is that
   there can be multiple occurrences of a new header indexed by this
   specification in a single frame and the overhead on an octet each
   time for the Escape Dispatch would be prohibitive.

   A Page (say Page N) is is said to be active once the Page N Paging
   Dispatch is parsed, and as long as no other Paging Dispatch is
   parsed.

   The Dispatch bits defined in Page 0 by [RFC4944] are free to be
   reused in Pages 1 to 15.





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4.  Page 1 Paging Dispatch

   This specification defines some special properties for Page 1,
   detailed below:

      The Dispatch bits defined in Page 0 for the Compression Format for
      IPv6 Datagrams over IEEE 802.15.4-Based Networks [RFC6282] are
      defined with the same values in Page 1 so there is no need to
      switch context back from Page 1 to Page 0 to address LOWPAN_IPHC
      and LOWPAN_NHC.

      Mesh Headers represent Layer-2 information and are processed
      before any Layer-3 information that is encoded in Page 1.  If a
      6LoWPAN packet requires a Mesh header, the Mesh Header MUST always
      be placed in the packet before the first Page 1 Paging Dispatch,
      if any.

      For the same reason, Fragment Headers as defined in [RFC4944] MUST
      always be placed in the packet before the first Page 1 Paging
      Dispatch, if any.

      The NALP Dispatch Bit Pattern as defined in [RFC4944] is only
      defined for the first octet in the packet.  Switching back to Page
      0 for NALP inside a 6LoWPAN packet does not make sense.

      It results that there is no need so far for restoring the Page 0
      parsing context after a context was switched to Page 1, so the
      value for the Page 0 Paging Dispatch of 11110000 may not actually
      be seen in packets following the 6LoWPAN specifications that are
      available at the time of writing.

5.  Security Considerations

   The security considerations of [RFC4944] and [RFC6282] apply.

6.  IANA Considerations

   This document creates a IANA registry for the 6LoWPAN Routing Header
   Type, and assigns the following values:

      0..4 : RH3-6LoRH [RFCthis]

      5 : RPI-6LoRH [RFCthis]

      6 : IPinIP-6LoRH [RFCthis]






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7.  Acknowledgments

   The authors wish to thank Thomas Watteyne, Tengfei Chang, Martin
   Turon, James Woodyatt, Samita Chakrabarti, Jonathan Hui, Gabriel
   Montenegro and Ralph Droms for constructive reviews to the design in
   the 6lo Working Group.

8.  References

8.1.  Normative References

   [IEEE802154]
              IEEE standard for Information Technology, "IEEE std.
              802.15.4, Part. 15.4: Wireless Medium Access Control (MAC)
              and Physical Layer (PHY) Specifications for Low-Rate
              Wireless Personal Area Networks", 2015.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC4944]  Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler,
              "Transmission of IPv6 Packets over IEEE 802.15.4
              Networks", RFC 4944, DOI 10.17487/RFC4944, September 2007,
              <http://www.rfc-editor.org/info/rfc4944>.

   [RFC6282]  Hui, J., Ed. and P. Thubert, "Compression Format for IPv6
              Datagrams over IEEE 802.15.4-Based Networks", RFC 6282,
              DOI 10.17487/RFC6282, September 2011,
              <http://www.rfc-editor.org/info/rfc6282>.

8.2.  Informative References

   [RFC7102]  Vasseur, JP., "Terms Used in Routing for Low-Power and
              Lossy Networks", RFC 7102, DOI 10.17487/RFC7102, January
              2014, <http://www.rfc-editor.org/info/rfc7102>.

   [RFC7228]  Bormann, C., Ersue, M., and A. Keranen, "Terminology for
              Constrained-Node Networks", RFC 7228,
              DOI 10.17487/RFC7228, May 2014,
              <http://www.rfc-editor.org/info/rfc7228>.

Author's Address







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   Pascal Thubert (editor)
   Cisco Systems
   Building D - Regus
   45 Allee des Ormes
   BP1200
   MOUGINS - Sophia Antipolis  06254
   FRANCE

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









































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