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Network Working Group                                        K. Kim, Ed.
Internet-Draft                                                    S. Yoo
Expires: January 10, 2006                                         H. Kim
                                                         Ajou University
                                                     S. Daniel Park, Ed.
                                                     SAMSUNG Electronics
                                                                  J. Lee
                                                                     NCA
                                                            July 9, 2005


                      Interoperability of 6LoWPAN
              draft-daniel-6lowpan-interoperability-01.txt

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Copyright Notice

   Copyright (C) The Internet Society (2005).

Abstract

   This document specifies the gateway architecture for the





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   interoperability between 6LoWPAN and external IPv6 networks.  The
   gateway does the compression and decompression of IPv6 packets and
   performs the mapping between 16 bit short addresses and the IPv6
   addresses for both the external IPv6 networks and 6LowPAN,
   respectively.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
     2.1   Requirements notation  . . . . . . . . . . . . . . . . . .  4
   3.  Gateway Architecture for Interoperability  . . . . . . . . . .  4
     3.1   Mapping Tables . . . . . . . . . . . . . . . . . . . . . .  5
       3.1.1   Internal Device Address Mapping Table  . . . . . . . .  6
       3.1.2   External Device Address Mapping Table  . . . . . . . .  6
     3.2   Registration . . . . . . . . . . . . . . . . . . . . . . .  7
     3.3   Multiple Gateways  . . . . . . . . . . . . . . . . . . . .  7
   4.  Header Compression . . . . . . . . . . . . . . . . . . . . . .  7
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  7
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . .  7
   7.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . .  7
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  7
       Authors' Addresses . . . . . . . . . . . . . . . . . . . . . .  8
       Intellectual Property and Copyright Statements . . . . . . . . 10



























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1.  Introduction

   6LoWPAN is an IPv6 based low-power wireless personal area network
   which is comprised of devices that conform to  the IEEE 802.15.4-2003
   standard[ieee802.15.4].  As described in [I-D.kushalnagar-lowpan-
   goals-assumptions], there are several issues to be solved for
   enabling IP communication between 6LoWPAN devices.  The limited
   packet size of 6LoWPANs is one of them; The PDU size of IEEE 802.15.4
   is 127 octets while the MTU size of IPv6 packets is 1280 octets.
   [I-D.montenegro-lowpan-ipv6-over-802.15.4] introduces the adaption
   layer of fragmentation and reassembly for IPv6 packets, while
   providing a header compression scheme for reducing the size of the
   IPv6 header.

   The issue proposed in this document is about the interoperability
   between the external IPv6 networks and 6LoWPAN.  As shown in
   [I-D.kushalnagar-lowpan-goals-assumptions], it is obvious that the
   interoperability is one of the very basic requirements of providing
   IP connectivity to 6LoWPAN.  This document specifies the gateway
   architecture for the interoperability.  The gateway does the
   compression and decompression of IPv6 packets and performs the
   mapping between 16 bit short addresses and the IPv6 addresses for
   both the external IPv6 networks and 6LowPAN, respectively.

   [I-D.montenegro-lowpan-ipv6-over-802.15.4] didn't define transmission
   between external IPv6 networks and 6LoWPAN.  For external IPv6
   packets, it cannot compress the address of the packets.  So, the
   mapping between 16-bit short addresses and the IPv6 addresses is
   necessary in order to communicate with external IPv6 networks.
   Notice that the mapping is not about 64-bit extend addresses but 16-
   bit short addresses.  The reason is why using 16-bit short addresses
   is more efficient for the transmission than 64-bit extend addresses.
   So, this document describes the mapping 16-bit short addresses from
   the addresses for 6LoWPAN as well as the mapping for external IPv6
   networks.

   This document is based on [I-D.montenegro-lowpan-ipv6-over-802.15.4]
   for the adaptation layer of fragmentation and reassembly,  the
   stateless address auto-configuration based on EUI-64[EUI64], the IPv6
   link local address, the unicast address mapping, and the encoding of
   UDP header fields.

2.  Terminology








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   ET:
      Expiration Time
   IID:
      Interface IDentifier
   MAC:
      Media Access Control
   MTU:
      Maximum Transmission Unit
   PAN:
      Personal Area Network
   PDU:
      Protocol Data Unit

2.1  Requirements notation

   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].

3.  Gateway Architecture for Interoperability

   This section defines the gateway architecture for the
   interoperability between IPv6 networks and 6LoWPAN.  The gateway
   SHOULD do the fragmentation and reassembly at the sub-IP layer for
   external IPv6 packets to/from 6LoWPAN.  The main function of the
   fragmentation and reassembly is the same as in [I-D.montenegro-
   lowpan-ipv6-over-802.15.4] except that the traffic is come from/to
   the external IPv6 networks.

   The gateway SHOULD do the compression and decompression of IPv6
   packets in between IPv6 networks and 6LoWPAN.  The compression
   implies the dettaching the 64-bit address prefix from the destination
   address of an IPv6 packet coming from external IPv6 networks in order
   to obtain the EUI-64 identifier for the IEEE 802.15.4 destination.
   The decompression is the exact opposite operation to the compression.

   The gateway MAY further compress IPv6 packets by introducing or
   mapping (16-bit) short addresses for both the external IPv6 networks
   and 6LoWPAN.  The gateway MAY maintain mapping table(s) for this
   translation.  The mapping SHOULD be applied to both the IPv6
   addresses of external IPv6 networks and 6LoWPAN, while the mapping
   table entries for them are different from each other.  Notice that
   for 6LoWPAN devices, the mapping of a 16-bit short address is done
   for the EUI-64 identifier which is obtained by the above mentioned
   compression, not the 128-bit IPv6 address.  In this document, we
   defines two mapping table types for external IPv6 networks and
   6LoWPAN which will be described in Section 3.1.




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   For communicating with external IPv6 networks, there are two possible
   traffic: inbound traffic from an external IPv6 network to an internal
   6LoWPAN and outbound traffic from an internal 6LoWPAN to an external
   IPv6 network.

   Inbound traffic
      For the destination address of an inbound IPv6 packet, the gateway
      maps the IID of the destination to the corresponding (16-bit)
      short address using the internal device address mapping table.  In
      a compressed packet, the short address is put into the 'Address of
      final destination' field of the final destination field and the
      'S' field is set 1 in sub-IP.  The assignment of the 16-bit short
      address for an IID depends on the assignment strategy which is out
      of scope of this document.  For the source address, the gateway
      assigns and maps an external 16-bit short address in the external
      device address mapping table.  The assignment strategy for an
      external short address is TBD.  The external short address will be
      deleted after the expiration time which will be described in
      Section 3.1.2.

      Note:  [I-D.montenegro-lowpan-ipv6-over-802.15.4] did not describe
         about the source address of the originator though do about the
         final destination field.  The context for the source address is
         valid if and only if it defines the source address of the
         originator in sub-IP.

   Outbound traffic
      The outbound traffic can be classified by the following two
      categories.  First category is the reply traffic for the above
      mentioned inbound traffic.  In this case, a 6LoWPAN device can use
      16-bit short addresses for both destination and source addresses.
      Notice that there is an assigned external short address in the
      external device address mapping table prior to the reply traffic
      and the definition for the source addressof the originator in
      sub-IP.  The outbound traffic should arrive at the gateway before
      the expiration time of the external short address.  The operation
      for the outbound traffic after the expiration is TBD.  Second
      category is the originating outbound traffic.  Because there is no
      mapped external short address for the destination of external IPv6
      networks, there can be no compression for the destination in this
      case.

3.1  Mapping Tables

   The gateway MAY have the internal and external device address mapping
   tables.





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3.1.1  Internal Device Address Mapping Table

   This table consists of 64-bit interface identifier (IID) and 16-bit
   short address.  This table MUST contain the mapping information of
   all the devices in 6LoWPAN.  The maximum size of the mapping table is
   2^16 entries.  The case of multiple gateways (i.e. multiple mapping
   tables) is dealt in Section 3.3.



                         64 bits           16 bits
              +--------------------------------------+
              |            IID          | Short Addr.|
              +--------------------------------------+

          <Fig. 1. Internal Device Address Mapping Table>



   Interface Identifier:  The 64 bit IID assigned to each 6LoWPAN
      device.

   Short Address:  The 16 bit short address assigned to each 6LoWPAN
      device.

3.1.2  External Device Address Mapping Table

   This table consists of 128-bit IPv6 address, 16-bit short address and
   ET(Expiration Time).



                       128 bits                 16 bits     8 bits
       +-------------------------------------+------------+-------+
       |               IPv6 Addr.            | Short Addr.|  ET   |
       +-------------------------------------+------------+-------+

             <Fig. 2. External Device Address Mapping Table>



   IPv6 Address:  The IPv6 address of the external device.

   Short Address:  The 16 bit short address for the external IPv6
      address.






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   ET:  The expiration time field.

3.2  Registration

   The gateway maintains the internal device mapping table for the
   mapping of 16 bit short address for all devices in the 6LoWPAN.  In
   order to setup the table, there should be a registration procedure
   which is TBD.

3.3  Multiple Gateways

   In this document, we assume that there is one gateway for a 6LoWPAN,
   even though the number of gateways is not restricted.  The more
   communication with external IPv6 networks, the more overheads the
   gateway undergo.  One of the methods reducing the overheads is
   distributing the burden over multiple gateways.  We will cover such
   issues as distributed mapping of 16-bit short addresses by multiple
   gateways and (on-demand or hierarchical) routing and tunneling
   between gateways, in future revision.

4.  Header Compression

   The method of the header compression follows [I-D.montenegro-
   lowpan-ipv6-over-802.15.4].  The size of the address in the 'M' field
is reduced because the gateway maps 64-bit link-layer addresses to
   16-bit short addresses.

5.  IANA Considerations

   There is at the time of this publication no IANA consideration.

6.  Security Considerations

   TBD

7.  Acknowledgements

   Thanks to Prof. Byeong-Hee Roh, Jea Tek Ryu, and Minho Lee for their
   useful discussions and supports for writing this document.

8.  References

   [EUI64]    IEEE
              http://standards.ieee.org/regauth/oui/tutorials/
              EUI64.html, "GUIDELINES FOR 64-BIT GLOBAL IDENTIFIER
              (EUI-64) REGISTRATION AUTHORITY".




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   [I-D.kushalnagar-lowpan-goals-assumptions]
              Kushalnagar, N. and G. Montenegro, "6LoWPAN: Overview,
              Assumptions, Problem Statement and Goals",
              draft-kushalnagar-lowpan-goals-assumptions-00 (work in
              progress), February 2005.

   [I-D.montenegro-lowpan-ipv6-over-802.15.4]
              Montenegro, G., "Transmission of IPv6 Packets over IEEE
              802.15.4 Networks",
              draft-montenegro-lowpan-ipv6-over-802.15.4-02 (work in
              progress), February 2005.

   [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.

   [ieee802.15.4]
              IEEE Compure Society, "IEEE Std. 802.15.4-2003", IEEE Std.
              802.15.4-2003, October 2003.


Authors' Addresses

   Ki-Hyung Kim
   Ajou University
   San 5 Wonchun-dong, Yeongtong-gu
   Suwon-si, Gyeonggi-do  442-749
   KOREA

   Phone: +82 31 219 2433
   Email: kkim86@ajou.ac.kr


   Seung Wha Yoo
   Ajou University
   San 5 Wonchun-dong, Yeongtong-gu
   Suwon-si, Gyeonggi-do  442-749
   KOREA

   Phone: +82 31 219 1603
   Email: swyoo@ajou.ac.kr








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   Hee Jung Kim
   Ajou University
   San 5 Wonchun-dong, Yeongtong-gu
   Suwon-si, Gyeonggi-do  442-749
   KOREA

   Phone: +82 31 219 1895
   Email: rla81@ajou.ac.kr


   Soohong Daniel Park
   Mobile Platform Laboratory, SAMSUNG Electronics
   416 Maetan-3dong, Yeongtong-gu
   Suwon-si, Gyeonggi-do  442-742
   KOREA

   Phone: +82 31 200 4508
   Email: soohong.park@samsung.com


   Jae Ho Lee
   National Computerization Agency
   NCA Bldg, 77, Mugyo-dong, Chung-ku
   Seoul,   100-775
   KOREA

   Phone: +82 2 2131 0250
   Email: ljh@nca.or.kr























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