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Internet Engineering Task Force (IETF)                   P. Thubert, Ed.Request for Comments: 8025                                         CiscoUpdates:4944                                                  R. CragieCategory: Standards Track                                            ARMISSN: 2070-1721                                            November 2016IPv6 over Low-Power Wireless Personal AreaNetwork (6LoWPAN) Paging DispatchAbstract   This specification updatesRFC 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 inSection 2 of RFC 7841.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://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 toBCP 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 2016Table of Contents1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .22.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .33.  UpdatingRFC 4944 . . . . . . . . . . . . . . . . . . . . . .34.  Page 1 Paging Dispatch  . . . . . . . . . . . . . . . . . . .45.  Security Considerations . . . . . . . . . . . . . . . . . . .56.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .56.1.  Page Switch Dispatch Types  . . . . . . . . . . . . . . .56.2.  New Column in Dispatch Type Registry  . . . . . . . . . .57.  References  . . . . . . . . . . . . . . . . . . . . . . . . .77.1.  Normative References  . . . . . . . . . . . . . . . . . .77.2.  Informative References  . . . . . . . . . . . . . . . . .7   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .8   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .81.  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 20162.  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.  UpdatingRFC 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.  InSection 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 20165.  Security Considerations   The security considerations of [RFC4944] and [RFC6282] apply.6.  IANA Considerations6.1.  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 20167.  References7.1.  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 2016Acknowledgments   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.comThubert & Cragie             Standards Track                    [Page 8]