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rfc:rfc8025

Internet Engineering Task Force (IETF) P. Thubert, Ed. Request for Comments: 8025 Cisco Updates: 4944 R. Cragie Category: Standards Track ARM ISSN: 2070-1721 November 2016

             IPv6 over Low-Power Wireless Personal Area
                 Network (6LoWPAN) Paging Dispatch

Abstract

 This specification updates RFC 4944 to introduce a new context switch
 mechanism for IPv6 over Low-Power Wireless Personal Area Network
 (6LoWPAN) compression, expressed in terms of Pages and signaled by a
 new Paging Dispatch.

Status of This Memo

 This is an Internet Standards Track document.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It represents the consensus of the IETF community.  It has
 received public review and has been approved for publication by the
 Internet Engineering Steering Group (IESG).  Further information on
 Internet Standards is available in Section 2 of RFC 7841.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 http://www.rfc-editor.org/info/rfc8025.

Copyright Notice

 Copyright (c) 2016 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
 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.

Thubert & Cragie Standards Track [Page 1] RFC 8025 6LoWPAN Paging Dispatch November 2016

Table of Contents

 1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
 2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
 3.  Updating RFC 4944 . . . . . . . . . . . . . . . . . . . . . .   3
 4.  Page 1 Paging Dispatch  . . . . . . . . . . . . . . . . . . .   4
 5.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
 6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   6.1.  Page Switch Dispatch Types  . . . . . . . . . . . . . . .   5
   6.2.  New Column in Dispatch Type Registry  . . . . . . . . . .   5
 7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
   7.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
   7.2.  Informative References  . . . . . . . . . . . . . . . . .   7
 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .   8
 Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1. Introduction

 The design of Low-Power and Lossy Networks (LLNs) is generally
 focused on saving energy, which is often a very constrained resource.
 Other constraints, such as memory capacity and duty cycle
 restrictions on LLN devices, usually derive from that primary
 concern.  Energy is often available only from primary batteries that
 are expected to last for years or is scavenged from the environment
 in very limited amounts.  Any protocol that is intended for use in
 LLNs must be designed with a primary focus on saving energy, which is
 a strict requirement.
 Controlling the amount of data transmission is one possible means of
 saving 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 [IEEE.802.15.4] is
 limited to 127 bytes per frame.  The need to compress IPv6 packets
 over IEEE 802.15.4 led to the 6LoWPAN Header Compression (6LoWPAN-HC)
 [RFC6282] work.
 As more and more protocols need to be compressed, the encoding
 capabilities of the original dispatch defined in the 6LowPAN
 adaptation-layer framework ([RFC4944] and [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 mechanism.

Thubert & Cragie Standards Track [Page 2] RFC 8025 6LoWPAN Paging Dispatch November 2016

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].
 The terminology used in this document is consistent with and
 incorporates that described in "Terms Used in Routing for Low-Power
 and Lossy Networks" [RFC7102] and "Terminology for Constrained-Node
 Networks" [RFC7228].

3. Updating RFC 4944

 This document adapts 6LoWPAN while maintaining backward compatibility
 with IPv6 over IEEE 802.15.4 [RFC4944] by introducing the concept of
 a "parsing 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 11 11xxxx, 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.
 The Dispatch bits defined in [RFC4944] are used in Page 0 and are
 free to be reused in Pages 1 to 15.  In Section 4, this specification
 allocates some values in Page 1 and leaves the rest open for future
 allocations.
 Values made available by this specification in Pages 1 to 14 are to
 be assigned for new protocols whereas Page 15 is reserved for
 Experimental Use [RFC5226].

Thubert & Cragie Standards Track [Page 3] RFC 8025 6LoWPAN Paging Dispatch November 2016

 Note: This specification does not use the Escape Dispatch, which
 extends Page 0 to more values, but rather allocates another Dispatch
 Bit Pattern (11 11xxxx) 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 said to be active once the Page N Paging
 Dispatch is parsed, and it remains active until another Paging
 Dispatch is parsed.

4. Page 1 Paging Dispatch

 This specification defines some special properties for Page 1,
 detailed below:
    The Dispatch bits defined for LOWPAN_IPHC by 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 from Page 1 to Page 0 to decode a packet
    that is encoded per [RFC6282].
    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.
    As a result, there is no need to restore the Page 0 parsing
    context after a context was switched to Page 1, so the value for
    the Page 0 Paging Dispatch of 11 110000 may not actually occur in
    those packets that adhere to 6LoWPAN specifications available at
    the time of writing this specification.

Thubert & Cragie Standards Track [Page 4] RFC 8025 6LoWPAN Paging Dispatch November 2016

5. Security Considerations

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

6. IANA Considerations

6.1. Page Switch Dispatch Types

 This document allocates 16 values for "Page switch" from the
 "Dispatch Type Field" registry that was created by [RFC4944].  The
 allocated values are from 11 110000 through 11 111111 and represent
 Page Numbers 0 through 15 as discussed in this document.

6.2. New Column in Dispatch Type Registry

 This document extends the "Dispatch Type Field" registry, which was
 created by [RFC4944] and updated by [RFC6282], by adding a new column
 called "Page".
 This document defines 16 Pages, "Page 0" to "Page 15".
 The preexisting registry content is assigned to "Page 0".
 This document also associates the Dispatch type field values that are
 allocated for LOWPAN_IPHC by [RFC6282] to Page 1.  These values range
 from 01 100000 through 01 111111 and have the same definition in Page
 1 as they do in Page 0; as a result, Page 0 and Page 1 are grouped
 together in the registry for this range.
 Values ranging from 00 000000 to 11 101111 in Page 15 (that is, all
 of Page 15 except the space used for Page switch) are reserved for
 Experimental Use [RFC5226] and shall not be assigned.
 Figure 2 represents the updates to the registry as described above.
 Refer to <http://www.iana.org/assignments/_6lowpan-parameters> for
 the complete list of updates.

Thubert & Cragie Standards Track [Page 5] RFC 8025 6LoWPAN Paging Dispatch November 2016

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Bit Pattern | Page | Header Type | Reference | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | 0 | NALP | RFC 4944, | | | | | this document | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 00 xxxxxx | 1-14 | Unassigned | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-| | | 15 | Reserved for | this document | | | | Experimental Use | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | 0 | ESC | RFC 6282, | | | | | this document | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 01 000000 | 1-14 | Unassigned | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-| | | 15 | Reserved for | this document | | | | Experimental Use | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     ...                   ...

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | 0-1 | LOWPAN_IPHC | RFC 6282, | | | | | this document | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 01 1xxxxx | 2-14 | Unassigned | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-| | | 15 | Reserved for | this document | | | | Experimental Use | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     ...                   ...

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 11 11xxxx | 0-15 | Page switch | this document | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

               Figure 2: Integrating the New Page Column
 Future assignments in these registries are to be coordinated via IANA
 under the policy of "Specification Required" [RFC5226].  It is
 expected that this policy will allow for other (non-IETF)
 organizations to more easily obtain assignments.

Thubert & Cragie Standards Track [Page 6] RFC 8025 6LoWPAN Paging Dispatch November 2016

7. References

7.1. Normative References

 [IEEE.802.15.4]
            IEEE, "IEEE Standard for Low-Rate Wireless Networks",
            IEEE 802.15.4-2015, DOI 10.1109/IEEESTD.2016.7460875,
            <http://ieeexplore.ieee.org/document/7460875/>.
 [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>.
 [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
            IANA Considerations Section in RFCs", BCP 26, RFC 5226,
            DOI 10.17487/RFC5226, May 2008,
            <http://www.rfc-editor.org/info/rfc5226>.
 [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>.

7.2. 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>.

Thubert & Cragie Standards Track [Page 7] RFC 8025 6LoWPAN Paging Dispatch November 2016

Acknowledgments

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

Authors' Addresses

 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
 Robert Cragie
 ARM Ltd.
 110 Fulbourn Road
 Cambridge  CB1 9NJ
 United Kingdom
 Email: robert.cragie@gridmerge.com

Thubert & Cragie Standards Track [Page 8]

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