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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material or to cite them other than as "work in progress."
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
Provisions Relating to IETF Documents
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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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