Internet DRAFT - draft-turner-dhcp-6co
draft-turner-dhcp-6co
individual submission R. Turner
Internet-Draft Landis+Gyr
Intended status: Standards Track June 2015
Expires: November 23, 2015
DHCPv6 Option for Configuration of 6LoWPAN Compression Contexts
draft-turner-dhcp-6co-00
Abstract
This document specifies a DHCPv6 option to configure hosts on a
6LoWPAN with IPv6 address compression information as required by
stateful compression methods specified in RFC 6282. The option
provides up to 16 prefixes that can be associated with specific
instances of IPv6 address compression used in 6LoWPANs. Each prefix
can be a variable length of bits, and includes a validity lifetime as
well.
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This Internet-Draft will expire on November 2, 2015.
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
1. Introduction
RFC 6282 describes a procedure for the compression of IPv6 addresses
in IP headers, and this same technique can be used to compress
arbitrary IPv6 addresses. The compression algorithms contain
default, stateless methods, as well as "stateful" address compression
based on a set of compression "contexts". However, the method by
which 6LoWPAN nodes acquire these contexts is out of scope of RFC
6282. RFC 6775 introduced a method by which router advertisements
can include "6LowPAN Context Options" that communicate context
information to devices on the 6LoWPAN network. RFC 6775 also
introduced a way to limit the rate of multicast router advertisements
to make these router advertisements more friendly to constrained
LoWPANs. These mechanisms allow a stateless auto-configuration
option for LoWPANs. DHCPv6 is both a stateful method for address
configuration, as well as stateless alternative for configuration of
6LoWPAN devices. DHCPv6 provides extensibility through the support
of TLV options in the protocol. This document specifies such a
DHCPv6 option for configuring 6LoWPAN compression contexts.
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],
[RFC3315] and [RFC6282]. The terminology and concepts described in
these documents will assist in the reading of this document.
3. DHCP Option format for 6LowPAN Compression Contexts
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_V6_6CO | Option Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Context Length | Res |C| CID | Valid Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. Context Prefix .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: 6LoWPAN Context Option Format
Figure 1
The description of the option fields is provided below:
o OPTION_V6_6CO: The option-code per RFC 3315 (TBA by IANA)
o Option Length: 16-bit unsigned length (in bytes) of the entire
option contents, including the type and length fields
o Context Length: 8-bit unsigned integer. The number (0 - 128) of
valid leading bits in the "Context Prefix" field.
o Res: This field is currently unused. It MUST be initialized to
zero by the server and MUST be ignored by the DHCPv6 client.
o CID: 4-bit Context Identifier for this prefix information. The
CID is used by context-based header compression as specified in
[RFC6282].
o Valid Lifetime: 16-bit unsigned integer. The length of time in
units of 60 seconds (relative to the time the option is received)
that the context is valid for the purpose of header compression or
decompression. A value of zero indicates that no specific
validity lifetime is specified (prefix validity does not expire).
o Context Prefix: The IPv6 prefix or address corresponding to the
CID field. This field is padded with zeros in order to make the
option a multiple of 8-bytes
There is one option per IPv6 context prefix, with each prefix option
containing a "CID" that provides the context identifier (or index) in
the range 0 to 15. This index is referred to by subsequent
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compressed IPv6 addresses to indicate which stateful prefix should be
used to either compress or decompress a particular IPv6 address.
4. DHCPv6 Client Behavior
Clients will utilize the OPTION_ORO (Option Request Option),
specifying the OPTION_V6_6CO option to be returned by the server, in
addition to any other required configuration parameters. Because of
the constrained nature of 6LoWPAN networks, clients are advised to
utilize the DHCPv6 Rapid Commit [RFC3315] option when requesting
DHCPv6 configuration.
5. DHCPv6 Server Behavior
Servers that support OPTION_V6_6CO are expected to be aware of the
existence of constrained networks that use the server during
configuration. Therefore servers SHOULD support the abbreviated
"Rapid Commit" packet exchange specified in [RFC3315].
6. Security Considerations
Any type of mis-configuration of the option described in this
document may cause re-routing of packets on a 6LoWPAN network, due to
the compression context being blindly trusted by DHCPv6 clients
requesting this option. The trust relationship necessary to create a
trusted binding of compression contexts and clients on the network
should be established by means other than that specified in this
document. This trust relationship should be binding for all such
configuration information transmitted from a DHCPv6 server to clients
requesting options. DHCPv6 traffic is traditionally communicated "in
the clear" on most networks, and in these scenarios where traffic is
neither encrypted nor integrity protected, man-in-the-middle attacks
are possible. However, in many 6LoWPAN deployment scenarios, these
networks include protection at layer-2 (for example, 802.15.4
encryption), including a "secure join" mechanism that protects these
networks from introducing unauthorized traffic onto the network
("rougue nodes"). In these types of networks, man-in-the-middle
attacks are less likely.
7. IANA Considerations
IANA is requested to assign one option code for OPTION_V6_6CO from
the "DHCP Option Codes" table of the Dynamic Host Configuration
Protocol for IPv6 (DHCPv6) Registry.
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8. References
[RFC6550] Winter, T., "RPL: IPv6 Routing Protocol for Low-Power and
Lossy Networks", RFC 6550, March 2012.
[RFC3315] Bound, J., "DHCP for IPv6", RFC 3315, July 2003.
[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.
Author's Address
Randy Turner
Landis+Gyr
30000 Mill Creek Ave
Suite 100
Alpharetta, GA 30022
US
Phone: +1 678 258 1292
Email: randy.turner@landisgyr.com
URI: http://www.landisgyr.com/
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