LPWAN                                                             X. Qin
Internet-Draft                                                   N. Kong
Intended status: Experimental                                      CNNIC
Expires: November 10, 2016                                   May 9, 2016


                    Data Aggregation Unit for LP-WAN
                         draft-qin-lpwan-dau-00

Abstract

   Connecting LP-WANs(Low-Power Wide Area Networks) to the Internet is
   expected to provide significant benefits to these networks in terms
   of interoperability, application deployment, and management,among
   others.  However, the specific characteristics of LP-WANs, such as
   very limited data unit size, and large-scale data sets make the
   network operation more complex: using one IP packet to send one LP-
   WAN data unit is a waste of bandwidth(because the packet header is
   much bigger than payload), and the large-scale LP-WAN data sets can
   also increase the Internet burden.  This specification defines a Data
   Aggregation Unit(DAU) for LP-WANs to aggregate small-size date units
   into bigger data chains so they can be sent through the Internet more
   efficiently.

Status of This Memo

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   This Internet-Draft will expire on November 10, 2016.

Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the
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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents



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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
     1.2.  Abbreviations . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Problem Statemate . . . . . . . . . . . . . . . . . . . . . .   4
   3.  L-DAU Scheme  . . . . . . . . . . . . . . . . . . . . . . . .   5
     3.1.  L-DAU Format  . . . . . . . . . . . . . . . . . . . . . .   5
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   5.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   7
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   The existing pilot deployments of LP-WANs have shown the huge
   potential and the industrial interest in their capabilities, such as
   in control and monitoring applications.  Examples of LPWAN
   technologies include LoRa, SigFox, IEEE 802.15.4k LECIM, DASH-7,
   Weightless, etc.  [I-D.minaburo-lp-wan-gap-analysis].  Connecting
   these LP-WANs to the Internet is expected to provide significant
   benefits to these networks in terms of interoperability, application
   deployment, and management, among others.  For these reasons, more
   and more LP-WAN owners are connecting their own LP-WANs to the
   Internet.




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   It is generally desirable that a given Data Unit(DU) generated by any
   LP-WANs can be sent through the Internet efficiently and quickly.
   However, the intrinsic characteristics of LP-WANs, very limited DU
   size and large-scale DU sets make the data transmission through
   Internet more complex.  In a nutshell, that may be a terrible waste
   of bandwidth if use one IP packet to send one LP-WAN Data Unit(LDU),
   because the packet header is much bigger than payload.And what's
   more, the LP-WAN usually consists of many nodes, so the large-scale
   data may increase the Internet burden.  This is the motivation for
   aggregating these small-size LDUs into a bigger data chain to improve
   the percentage of the payload in IP packet to make the information
   retrieval and dissemination more efficient.  For example,a ZigBee
   Cluster can aggregate several LDUs into a LDU chain and send them
   together as an atomic payload of the IP packet.  By doing this, the
   ZigBee Cluster doesn't need to initiate the transmission for every
   LDU as well as improve the proportion of the payload in the IP packet
   to increase the transmission efficiency.

   During transmission, the aggregator cannot do any processing on the
   LDUs and just encapsulates them into an aggregation chain.  During
   reception, the de-aggregator just opens the data chain and separately
   forwards them to the applications.

   This arrangement provides numerous benefits for LP-WAN
   applications(both transmitter and receiver): increased delivery
   efficiency, reduced transmission/receiving times, and improved
   quality of experience for LP-WAN Users.  Considering that a vast
   number of LP-WAN devices are,as of today,battery-powered,the DAU is
   also helpful for saving battery consumption.

1.1.  Terminology

   This document uses the following terms:

   Aggregator: Software entity which resides either in the system kernel
   or hardware aggregating one or more LDUs into an aggregation chain,
   the payload of the IP packet that is sent through the internet.  The
   aggregator is usually placed into transmitter device with cache
   capacity.

   De-aggregator: Software entity which resides either in the system
   kernel or hardware de-aggregating the LDU chain into seperate LDU,
   which comes from aggregator.  De-aggregator is usually placed into
   receiving device with cache capacity.

   Data Unit: Refers to data packets generated by LP-WANs in general,
   for example generated by LoRa, SigFox, IEEE 802.15.4k LECIM, etc.




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1.2.  Abbreviations

   o  DU:Data Unit

   o  LDU: LP-WAN Data Unit

   o  L-DAU: LP-WAN Data Aggregation Unit

2.  Problem Statemate

   LP-WAN technologies are a kind of constrained and challenged networks
   [RFC7228].

   o  very small frame payload as low as 12 bytes.  Typical traffic
      patterns are composed of a large majority of frames with payload
      size around 15 bytes and a small minority of up to 100 byte
      frames.

   o  ultra dense networks with thousands to tens of thousands of nodes.

   On the other side, the existing Internet technologies have their
   specific characteristics:

   o  IP header is usually more than 20 bytes[RFC6864],[RFC6973], and
      the Ethernet header is at least 14 bytes[RFC7796].

   o  TCP is a reliable and connection oriented transport
      mechanism[RFC7661].

   Therefore, it is obviously unwise to just encapsulate one LDU into
   the IP packet.  That's a waste of bandwidth and also increases
   Internet burdens.  However, no standards or open specifications
   currently exist to solve above problems.

   In the terminology of [RFC7228], these characteristics put LP-WANs
   into the "challenged network" category, and the intrinsic
   characteristics, current usages and architectures will allow the
   group to make and justify the design choices.  However, there also
   some desired properties:

   o  preserve the end-to-end communication principle.

   o  maintain independence from L2 technology.

   o  use or adapt protocols defined by IETF to this new environment
      that could be less responsive.

   o  use existing addressing spaces and naming schemes defined by IETF.



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   o  small message size, with potentially no L2 fragmentation.

   o  optimize the protocol stack in order to limit the number of
      duplicated functionalities; for instance acknowledgements should
      not be done at several layers.

   So,the L-DAU is proposed in this document to make the information
   retrieval and dissemination of LP-WANs more efficient as well as
   fully conforms to the principles proposed in [RFC7228].

3.  L-DAU Scheme

   The L-DAU service architecture is shown in Figure 1.  During
   transmission, a LDU is passed down from LPWAN application, and stored
   temporarily by the aggregator, then aggregated into a L-DUA.  During
   reception, a received L-DAU is de-aggregated into seperate LDUs and
   forwarded to the LP-WAN application.




            +--------------------+             +--------------------+ ^
          | |      LPWAN         | Frame Flow  |       LPWAN        | |
         S| | Application Lawer  |<----------->|    application     | |
         e| +--------------------+             +--------------------+ |g
         n| |       L-DAU        |             |       L-DAU        | |
         d| |    Aggregation     |             |     Aggregation    | |i
         i| +--------------------+             +--------------------+ |v
         n| |      Network       |             |      Network       | |i
         g| |       Layer        |             |       Layer        | |e
          | +--------------------+             +--------------------+ |c
          | |        PHY         |             |         PHY        | |e
          | |       Layer        |             |        Layer       | |R
          V +--------------------+             +--------------------+
                        Figure 1 L-DAU service architecture



3.1.  L-DAU Format

   A L-DAU consists of a sequence of one or more L-DAU subframes as
   shown in Figure 2.









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          +------------------+-----------------+------+------------------+
          | L-DAU subframe 1 | L-DAU subframe 2|  ... | L-DAU subframe n |
          +------------------+-----------------+------+------------------+
   Octets:     variable          variable                 variable


                           Figure 2 L-DAU format



   Each L-DAU subframe consists of a LDU delimiter followed by a LDU.
   Except when a L-DAU subframe is the last one in a L-DAU.  The L-DAU
   length should be less than 65535 octets.  The LDU delimiter is 2
   octets in length and the structure of the LDU delimiter is defined in
   Figure 3.


   Bits:     B0    B1    B2   B7      B8          B15
          +-----------+-----------+---------------------+---------------+
          |  Reserved | LDU length| Delimiter Signature |       LDU     |
          +-----------+-----------+---------------------+---------------+

                              L-DAU Delimiter
 Octets:  <--------------------------------------------->     variable
                                   2

                           Figure 3 L-DAU subframe format



   The fields of the L-DAU delimiter are defined in Table 1.




















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               Table 1: L-DAU delimiter fields
     +-----------+--------+---------------------------------------------+
     |  Field    |  Size  |              Description                    |
     |           | (Bits) |                                             |
     +-----------+--------+---------------------------------------------+
     | Reserved  |   2    |                                             |
     +-----------+--------+---------------------------------------------+
     | LDU Length|   6    |  Length of the LDU in octets                |
     +-----------+--------+---------------------------------------------+
     |           |   8    |  Pattern that may be used to detect an L-DAU|
     | Delimiter |        |  delimiter when scanning for a delimiter.   |
     | Signature |        |  The unique pattern is set to the value     |
     |           |        |   0x7E.                                     |
     |           |        |                                             |
     +-----------+--------+---------------------------------------------+


   The purpose of the L-DAU delimiter is to locate the LDUs within the
   L-DAU.

4.  Security Considerations

   This document focuses on approach and the motivational for L-DUA, and
   does not analyze the associated threats.  Those threats will be
   discussed in future.

5.  Acknowledgments

   The authors wish to thank Linlin Zhou for her invaluable comments.

6.  References

6.1.  Normative References

   [RFC6864]  Touch, J., "Updated Specification of the IPv4 ID Field",
              RFC 6864, DOI 10.17487/RFC6864, February 2013,
              <http://www.rfc-editor.org/info/rfc6864>.

   [RFC6973]  Cooper, A., Tschofenig, H., Aboba, B., Peterson, J.,
              Morris, J., Hansen, M., and R. Smith, "Privacy
              Considerations for Internet Protocols", RFC 6973,
              DOI 10.17487/RFC6973, July 2013,
              <http://www.rfc-editor.org/info/rfc6973>.

   [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>.



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   [RFC7661]  Fairhurst, G., Sathiaseelan, A., and R. Secchi, "Updating
              TCP to Support Rate-Limited Traffic", RFC 7661,
              DOI 10.17487/RFC7661, October 2015,
              <http://www.rfc-editor.org/info/rfc7661>.

   [RFC7796]  Jiang, Y., Ed., Yong, L., and M. Paul, "Ethernet-Tree
              (E-Tree) Support in Virtual Private LAN Service (VPLS)",
              RFC 7796, DOI 10.17487/RFC7796, March 2016,
              <http://www.rfc-editor.org/info/rfc7796>.

6.2.  Informative References

   [PPSP-Charter]
              Y, Yan., "simulated-annealing algorithm", December 2009,
              <http://datatracker.ietf.org/wg/ppsp/charter/>.

Authors' Addresses

   Xiaowei Qin
   CNNIC
   4 South 4th Street, Zhongguancun, Haidian District
   Beijing, Beijing  100190
   China

   Phone: +86 10 5881 3689
   Email: qinxiaowei@cnnic.cn


   Ning Kong
   CNNIC
   4 South 4th Street, Zhongguancun, Haidian District
   Beijing, Beijing  100190
   China

   Phone: +86 10 5881 3147
   Email: kongning@cnnic.cn















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