Internet DRAFT - draft-turner-roll-dio-ctx

draft-turner-roll-dio-ctx







individual submission                                          R. Turner
Internet-Draft                                                Landis+Gyr
Intended status: Experimental                         September 28, 2015
Expires: March 31, 2016


           RPL DIO Option for Specifying Compression Contexts
                      draft-turner-roll-dio-ctx-00

Abstract

   This memo describes an option to be included in RPL DIO messages that
   specifies one or more compression contexts to be used for IPv6
   address compression.  A compression context specifies a particular
   IPv6 address prefix to be used in both IPv6 header compression, as
   well as generic compression use-cases.  The list of compression
   contexts is indexed by a compression context ID compatible with RFC
   6282.

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 March 31, 2016.

Copyright Notice

   Copyright (c) 2015 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
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   (http://trustee.ietf.org/license-info) in effect on the date of
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   include Simplified BSD License text as described in Section 4.e of



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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

1.  Introduction

   RFC 6550 [RFC6550] includes a "DODAG Information Object" (DIO)
   message that allows nodes within a particular DODAG instance to learn
   about configuration parameters specific to the DODAG instance.  The
   message includes fixed fields containing fundamental DODAG
   operational parameters, and also provides for optional fields that
   specify additional DODAG parameters.  The optional parameters are
   specified through type-length-value (TLV) extensions.  This memo
   proposes a new DIO option for specifying a list of compression
   contexts appropriate for addressing use-cases where IPv6 address
   compression is required.

1.1.  Requirements Language

   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] [RFC2119].

2.  Terminology

   This document primarily uses the terminology described in [RFC6550]
   [RFC6550], [RFC6282] [RFC6282], and [RFC6775] [RFC6775].

3.  Compression Context Option

   The 6CO option describes a particular IPv6 address prefix to assume
   for use-cases where IPv6 address compression is required.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Type      |     Length    |Context Length | Res |C|  CID  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |            Reserved           |        Valid Lifetime         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   .                                                               .
   .                       Context Prefix                          .
   .                                                               .
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                  Figure 1: 6LoWPAN Context Option Format

   Length:          8-bit unsigned integer.  The length of the option
                    (including the Type and Length fields) in units of



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                    8 bytes.  May be 2 or 3, depending on the length of
                    the Context Prefix field.

   Context Length:  8-bit unsigned integer.  The number of leading bits
                    in the Context Prefix field that are valid.  The
                    value ranges from 0 to 128.  If it is more than 64,
                    then the Length MUST be 3.

   C:               1-bit context Compression flag.  This flag indicates
                    if the context is valid for use in compression.  A
                    context that is not valid MUST NOT be used for
                    compression but SHOULD be used in decompression in
                    case another compressor has not yet received the
                    updated context information.  This flag is used to
                    manage the context life cycle based on the
                    recommendations in [RFC6775] Section 7.2.

   CID:             4-bit Context Identifier for this prefix
                    information.  The CID is used by context-based
                    header compression as specified in [RFC6282].  The
                    list of CIDs for a LoWPAN is configured on the 6LBR
                    that originates the context information for the
                    6LoWPAN.

   Reserved:        This field is unused. It MUST be initialized to zero
                    by the sender and MUST be ignored by the receiver

   Valid Lifetime:  16-bit unsigned integer. The length of time in units
                    of 60-seconds (relative to the time the packet is
                    received) that the context is vlaid for the purposes
                    of IPv6 address compression or decompression. A value
                    of all zero bits (0x0) indicates that this context
                    entry MUST be removed (deactivated) immediately.

   Context Prefix:  The IPv6 prefix or address corresponding to the CID
                    field.  The valid length of this field is included
                    in the Context Length field.  This field is padded
                    with zeros in order to make the option a multiple of
                    8 bytes.


4.  RPL Root Operation

   Valid compression contexts are provisioned into RPL root
   implementations in a manner outside the scope of this document.
   Contexts are provisioned as one or more prefix, prefix-length, and
   context-ID tuples, as described in RFC 6282.  Up to 16 tuples (0 to
   15) can be configured.  Each tuple will require one DIO option in a



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   DIO message, so if there are 8 context tuples configured, then a DIO
   message will contain 8 DIO compression context options.

5.  RPL Router and Leaf Operation

   RPL routers and leafs (henceforth referred to as 'nodes') receive DIO
   messages and extract the compression context option(s) from the DIO
   message.  The 'C' bit in the compression context option enables
   lifecycle management of the particular option according to section
   7.2 of RFC 6775.

6.  Security Considerations

   The introduction of compression contexts into a 6LoWPAN involves
   being able to trust the sender of the context information, as well as
   verifying that the context information has not been modified since
   transmission by a trusted sender.

   Confidentiality of context information is not considered a
   requirement.

   RPL provides an optional facility to secure RPL messages for
   confidentiality, authenticity, and integrity.  Using RPL security
   would satisfy the security requirements for the dissemination of
   compression context information.  Alternatively, if a 6LoWPAN network
   uses 802.15.4, then the security requirements of this memo would be
   met by using a "secure network join" method whereby some type of
   mutual authentication would be utilized so that 6LoWPAN nodes could
   trust DIO messages originating from the network.

7.  References

   [RFC6550]  Winter, T., Thubert, P., Brandt, A., Hui, J., Kelsey, R.,
              Levis, P., Pister, K., Struik, R., Vasseur, JP., and R.
              Alexander, "RPL: IPv6 Routing Protocol for Low-Power and
              Lossy Networks", RFC 6550, March 2012.

   [RFC6775]  Shelby, Z., Chakrabarti, S., Nordmark, E., and C. Bormann,
              "Neighbor Discovery Optimization for IPv6 over 6LoWPANs",
              RFC 6775, November 2012.

   [RFC6282]  Hui, J. and P. Thubert, "Compression Format for IPv6
              Datagrams over 802.15.4-Based Networks", RFC 6282,
              September 2011.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", RFC 2119, March 1997.




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Author's Address

   Randy Turner
   Landis+Gyr
   30000 Mill Creek Ave
   Suite 100
   Alpharetta, GA  30022
   US

   Phone: +1 678 258 1929
   Email: randy.turner@landisgyr.com
   URI:   http://www.landisgyr.com/







































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