roll Y. Doi
Internet-Draft TOSHIBA Corporation
Intended status: Standards Track M. Gillmore
Expires: January 1, 2016 Itron, Inc
June 30, 2015
MPL Parameter Configuration Option for DHCPv6
draft-ietf-roll-mpl-parameter-configuration-05
Abstract
This document defines a way to configure a parameter set for MPL
(Multicast Protocol for Low power and Lossy Networks) via a DHCPv6
option. MPL has a set of parameters to control its behavior, and the
parameter set is often configured as a network-wide parameter because
the parameter set should be identical for each MPL forwarder in an
MPL domain. Using the MPL Parameter Configuration Option defined in
this document, a network can be configured with a single set of MPL
parameters easily.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on January 1, 2016.
Copyright Notice
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document authors. All rights reserved.
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to this document. Code Components extracted from this document must
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. MPL Parameter Configuration Option . . . . . . . . . . . . . 3
2.1. MPL Parameter Configuration Option Format . . . . . . . . 3
2.2. DHCPv6 Client Behavior . . . . . . . . . . . . . . . . . 5
2.3. MPL Forwarder Behavior . . . . . . . . . . . . . . . . . 5
2.4. DHCPv6 Server Behavior . . . . . . . . . . . . . . . . . 6
2.5. DHCPv6 Relay Behavior . . . . . . . . . . . . . . . . . . 6
2.6. Operational Considerations . . . . . . . . . . . . . . . 6
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
4. Security Considerations . . . . . . . . . . . . . . . . . . . 7
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
5.1. Normative References . . . . . . . . . . . . . . . . . . 7
5.2. Informative References . . . . . . . . . . . . . . . . . 8
Appendix A. Update History . . . . . . . . . . . . . . . . . . . 8
Appendix B. Considerations on Inconsistent Parameter Set . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
Multicast Protocol for Low power and Lossy Networks (MPL)
[I-D.ietf-roll-trickle-mcast] defines a protocol to make a multicast
network among low-power and lossy networks, e.g., wireless mesh
networks. MPL has a set of parameters to control an MPL domain. The
parameters control the trade-off between end-to-end delay and network
utilization. In most environments, the default parameters are
acceptable. However, in some environments, the parameter set must be
configured carefully in order to meet the requirements of each
environment. According to the MPL document section 5.4, each
parameter in the set should be the same for all nodes within an MPL
domain, but the MPL document does not define a method to configure
the MPL parameter set.
Some managed wireless mesh networks may have a DHCP server to
configure network parameters. MPL parameter sets shall be considered
as a part of network parameters (nodes in an MPL domain should use an
identical parameter set). And a parameter set is required to
configure an MPL domain.
This document defines the way to distribute parameter sets for MPL
forwarders as a DHCPv6 [RFC3315] option. This document is intended
to follow [RFC7227] the guideline.
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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].
2. MPL Parameter Configuration Option
Per MPL domain, there are the following 10 parameters. An MPL domain
is defined by an MPL domain address.
o PROACTIVE_FORWARDING
o SEED_SET_ENTRY_LIFETIME
o DATA_MESSAGE_IMIN
o DATA_MESSAGE_IMAX
o DATA_MESSAGE_K
o DATA_MESSAGE_TIMER_EXPIRATIONS
o CONTROL_MESSAGE_IMIN
o CONTROL_MESSAGE_IMAX
o CONTROL_MESSAGE_K
o CONTROL_MESSAGE_TIMER_EXPIRATIONS
One network may have multiple MPL domains with different
configurations. To configure more than one MPL domain via DHCP,
there may be more than one MPL Parameter Configuration Option given
to DHCP clients by a DHCP server.
2.1. MPL Parameter Configuration Option Format
To distribute a configuration of an MPL domain or a default value for
all MPL domains (wildcard) under the network managed by the DHCP
server, this document defines a DHCPv6 option format as follows.
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_MPL_PARAMETERS | option_len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|P| Z | TUNIT | SE_LIFETIME |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DM_K | DM_IMIN | DM_IMAX |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DM_T_EXP | C_K | C_IMIN >
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>(cont'ed) | C_IMAX | C_T_EXP |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(if option_len = 32 )
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MPL Domain Address (128bits) >
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> (cont'ed) >
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> (cont'ed) >
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> (cont'ed) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
OPTION_MPL_PARAMETERS: DHCPv6 option identifier (not yet assigned).
option_len: Length of the option. It SHOULD be 16 (without MPL
domain address) or 32 (with MPL domain address).
P (1 bit): A flag to indicate PROACTIVE_FORWARDING. The flag is set
if PROACTIVE_FORWARDING is true.
Z (7 bits): Reserved. Should be 0.
TUNIT (unsigned 8-bit integer): Unit time of timer parameters
(SE_LIFETIME, and *_IMIN) in this option. 0 and 0xff are reserved
and SHALL NOT be used.
SE_LIFETIME (unsigned 16-bit integer): SEED_SET_ENTRY_LIFETIME/TUNIT
in milliseconds. 0 and 0xffff are reserved and SHALL NOT be used.
DM_K (unsigned 8-bit integer): DATA_MESSAGE_K.
DM_IMIN (unsigned 16-bit integer): DATA_MESSAGE_IMIN/TUNIT in
milliseconds. 0 and 0xffff are reserved and SHALL NOT be used.
DM_IMAX (unsigned 8-bit integer): DATA_MESSAGE_IMAX. 0 and 0xff are
reserved and SHALL NOT be used.
DM_T_EXP (unsigned 16-bit integer): DATA_MESSAGE_TIMER_EXPIRATIONS.
0 and 0xffff are reserved and SHALL NOT be used.
C_K (unsigned 8-bit integer): CONTROL_MESSAGE_K.
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C_IMIN (unsigned 16-bit integer): CONTROL_MESSAGE_IMIN/TUNIT in
milliseconds. 0 and 0xffff are reserved and SHALL NOT be used.
C_IMAX (unsigned 8-bit integer): CONTROL_MESSAGE_IMAX. 0 and 0xff
are reserved and SHALL NOT be used.
C_T_EXP (unsigned 16-bit integer): CONTROL_MESSAGE_TIMER_EXPIRATIONS
. 0 and 0xffff are reserved and SHALL NOT be used.
Note that all time values (Trickle timers and expiration periods) are
in TUNIT milliseconds precision. For example, if TUNIT is 20 and the
data message interval minimum (DATA_MESSAGE_IMIN) is 1000ms, then
DM_IMIN shall be set to 50.
2.2. DHCPv6 Client Behavior
Clients MAY request the MPL Parameter Configuration Option, as
described in [RFC3315], sections 17.1.1, 18.1.1, 18.1.3, 18.1.4,
18.1.5, and 22.7. As a convenience to the reader, we mention here
that the client includes requested option codes in the Option Request
Option.
Clients MUST discard the MPL Parameter Configuration Option if it is
invalid (e.g., it sets reserved bits).
2.3. MPL Forwarder Behavior
If a DHCPv6 client requests and receives the MPL Parameter
Configuration Option, the node SHOULD join the MPL domain given by
the option and act as an MPL forwarder. Note that there may be cases
in which a node may fail is to join a domain (or domains) due to
local resource constraints. Each joining node SHOULD configure its
MPL forwarder with the given parameter set for the MPL domain.
The priority of MPL Parameter Configurations applied to an MPL Domain
is as follows (high to low):
o Specific MPL Parameter Configuration to the MPL Domain
(option_len=32)
o Wildcard MPL Parameter Configuration (option_len=16)
o Default configuration given in the MPL specification.
There SHALL be no more than one MPL Parameter Configuration Option
for an MPL domain or the wildcard. Thus, the order of DHCPv6 options
in the packet has no effect on precedence.
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A node MAY leave an MPL domain if the following two conditions are
satisfied. 1) The MPL domain is configured by a DHCPv6 option from a
DHCPv6 server previously. 2) The node has received an updated MPL
Parameter Configuration Option without a configuration for the MPL
domain.
MPL parameters may be updated occasionally. With stateful DHCPv6,
updates can be done when the renewal timer expires. Information
Refresh Time Option [RFC4242] shall be used to keep each forwarder
updated.
To reduce periodic update traffic, a node may try to use a very long
interval between updates. In the case, reconfigure messages may be
used to keep forwarder parameter sets synchronized.
2.4. DHCPv6 Server Behavior
Sections 17.2.2 and 18.2 of [RFC3315] govern server operation in
regards to option assignment. As a convenience to the reader, we
mention here that the server will send the MPL Parameter
Configuration Option only if it was configured with specific values
for the MPL Parameter Configuration Option and the client requested
it.
Servers SHALL ignore an incoming MPL Parameter Configuration Option.
2.5. DHCPv6 Relay Behavior
It's never appropriate for a relay agent to add options to a message
heading toward the client, and relay agents don't actually construct
Relay-Reply messages anyway. There are no additional requirements
for relays.
2.6. Operational Considerations
A parameter set for an MPL domain SHOULD NOT be updated more often
than twice of Information Refresh Time, even if the clients use
longer Information Refresh Time to reduce DHCPv6 load on the network.
If a node with an MPL forwarder configured by the MPL Parameter
Configuration Option failed to refresh the option within twice the
Information Refresh Time, it SHALL suspend the MPL forwarders of the
MPL domains configured by the option. MPL forwarders configured by
other methods such as static configuration file SHALL NOT be
suspended.
3. IANA Considerations
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IANA is requested to assign one option code for OPTION_MPL_PARAMETERS
from the "DHCP Option Codes" table of the Dynamic Host Configuration
Protocol for IPv6 (DHCPv6) Registry.
4. Security Considerations
There are detailed discussion on security threats on DHCPv6 in
Section 23 of RFC3315 [RFC3315] and Section 23 of RFC7227 [RFC7227].
In addition, a forged MPL parameter configuration may cause excessive
layer-2 broadcasting. Implementations should set reasonable bounds
for each parameter. For example, not too high DM/C_K, not too low DM
/C_IMIN, etc. These bounds may be implementation dependent or may be
derived from MAC/PHY specifications. DHCPv6 server and client
implementations need to take care in setting reasonable bounds for
each parameter in order to avoid overloading the network.
The DHCP server or the network itself should be trusted by some means
such as DHCPv6 authentications described in Section 21 of RFC3315
[RFC3315]. However, ROLL environment may expect less computing
resource, and DHCPv6 authentication may not available. In such
cases, other methods for security should be applied to a ROLL
network. Some ROLL specification such as ZigBee IP [ZigBeeIP]
expects RFC5191 [RFC5191] to authenticate joining nodes and all nodes
in the network can be trusted. To protect attacks from outside of
the network, unneccessary DHCPv6 packets should be filtered on the
border router between the ROLL network and the Internet.
5. References
5.1. Normative References
[I-D.ietf-roll-trickle-mcast]
Hui, J. and R. Kelsey, "Multicast Protocol for Low power
and Lossy Networks (MPL)", draft-ietf-roll-trickle-
mcast-12 (work in progress), June 2015.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
and M. Carney, "Dynamic Host Configuration Protocol for
IPv6 (DHCPv6)", RFC 3315, July 2003.
[RFC4242] Venaas, S., Chown, T., and B. Volz, "Information Refresh
Time Option for Dynamic Host Configuration Protocol for
IPv6 (DHCPv6)", RFC 4242, November 2005.
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[RFC7227] Hankins, D., Mrugalski, T., Siodelski, M., Jiang, S., and
S. Krishnan, "Guidelines for Creating New DHCPv6 Options",
BCP 187, RFC 7227, May 2014.
5.2. Informative References
[RFC5191] Forsberg, D., Ohba, Y., Patil, B., Tschofenig, H., and A.
Yegin, "Protocol for Carrying Authentication for Network
Access (PANA)", RFC 5191, May 2008.
[ZigBeeIP]
ZigBee Alliance, "ZigBee IP Specification", Mar 2014.
Appendix A. Update History
Updates on draft-ietf-roll-mpl-configuration-03 to draft-ietf-roll-
mpl-configuration-05:
o fixed *_IMAX definition as RFC6206 defines
o fixed *_EXP definition as draft-ietf-roll-trickle-mcast defines
o added references to RFC3315 and RFC7227 in security considerations
section
o added a paragraph on security consideration according to secdir
review
o fixed some nits and updated references
Updates on draft-ietf-roll-mpl-configuration-03 to draft-ietf-roll-
mpl-configuration-04:
o References updated (Non-normative -> Informative)
o IANA section is updated to make clear request of option ID
o Reserved numbers are clearly denoted
Updates on draft-ietf-roll-mpl-configuration-02 to draft-ietf-roll-
mpl-configuration-03:
o References updated
o Removed reference for DHCPv6 stateless reconfiguration as it has
expired
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Updates on draft-ietf-roll-mpl-configuration-01 to draft-ietf-roll-
mpl-configuration-02:
o Short unsigned floating point is dropped (#159)
o Packed value is removed and now every value has its own byte(s)
(#159)
Updates on draft-ietf-roll-mpl-configuration-00 to draft-ietf-roll-
mpl-configuration-01:
o Operational considerations (normative) and appendix considerations
(non-normative) are added (Issue #157)
o More control on nodes / allow constrained nodes to ignore the
configuration: "the node s/SHOULD/MAY/ join the MPL domain given
by the option" (Issue #158)
Updates on draft-doi-roll-mpl-configuration-05 to draft-ietf-roll-
mpl-configuration-00:
o I-D renamed.
Appendix B. Considerations on Inconsistent Parameter Set
This draft introduces dynamic update of MPL parameters. Because the
update process is not synchronized, nodes may have inconsistent
parameter sets.
Inconsistent parameter set may reduce performance. On the other
hand, this situation will work as long as both parameter sets are
reasonable parameter sets for a given communication load. As the
motivations for parameter update include update of the environment,
node density, or communication load, operators of MPL networks shall
be aware of unupdated nodes and make sure old and new parameter sets
are reasonable for the expected refresh intervals.
Authors' Addresses
Yusuke Doi
TOSHIBA Corporation
Komukai Toshiba Cho 1
Saiwai-Ku
Kawasaki, Kanagawa 2128582
JAPAN
Phone: +81-45-342-7230
Email: yusuke.doi@toshiba.co.jp
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Matthew Gillmore
Itron, Inc
2111 N Molter Rd.
Liberty Lake, WA 99019
USA
Email: matthew.gillmore@itron.com
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