Internet DRAFT - draft-ietf-roll-mpl-parameter-configuration
draft-ietf-roll-mpl-parameter-configuration
roll Y. Doi
Internet-Draft TOSHIBA Corporation
Intended status: Standards Track M. Gillmore
Expires: May 5, 2016 Itron, Inc
November 2, 2015
MPL Parameter Configuration Option for DHCPv6
draft-ietf-roll-mpl-parameter-configuration-08
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 easily be configured with a single set
of MPL parameters.
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
Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months
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time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on May 5, 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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publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
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to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
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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 . . . . . . . . . . . . . . . . . 6
2.4. DHCPv6 Server Behavior . . . . . . . . . . . . . . . . . 7
2.5. DHCPv6 Relay Behavior . . . . . . . . . . . . . . . . . . 7
2.6. Operational Considerations . . . . . . . . . . . . . . . 7
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
4. Security Considerations . . . . . . . . . . . . . . . . . . . 8
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.1. Normative References . . . . . . . . . . . . . . . . . . 9
5.2. Informative References . . . . . . . . . . . . . . . . . 9
Appendix A. Update History (TO EDITORS: this section is intended
to be removed before this document becomes an RFC) . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
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
As stated in Section 5.4 of [I-D.ietf-roll-trickle-mcast], there are
the following 10 parameters per MPL domain. An MPL domain is defined
by an MPL domain address, as described in Section 2 of
[I-D.ietf-roll-trickle-mcast].
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 |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DM_K | DM_IMIN | DM_IMAX |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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, which is 16 of no MPL domain
address is present, or 32 if there is an 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 for future use. Servers MUST set them to zero.
Clients SHOULD ignore the bits set.
TUNIT (unsigned 8-bit integer): Unit time of timer parameters
(SE_LIFETIME, and *_IMIN) in this option. 0 and 0xff are reserved
and MUST NOT be used.
SE_LIFETIME (unsigned 16-bit integer): SEED_SET_ENTRY_LIFETIME/TUNIT
in milliseconds. 0 and 0xffff are reserved and MUST 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 MUST NOT be used.
DM_IMAX (unsigned 8-bit integer): DATA_MESSAGE_IMAX. The actual
maximum timeout is described as a number of doublings of
DATA_MESSAGE_IMIN, as described in [RFC6206] Section 4.1. 0 and
0xff are reserved and MUST NOT be used.
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DM_T_EXP (unsigned 16-bit integer): DATA_MESSAGE_TIMER_EXPIRATIONS.
0 and 0xffff are reserved and MUST NOT be used.
C_K (unsigned 8-bit integer): CONTROL_MESSAGE_K.
C_IMIN (unsigned 16-bit integer): CONTROL_MESSAGE_IMIN/TUNIT in
milliseconds. 0 and 0xffff are reserved and MUST NOT be used.
C_IMAX (unsigned 8-bit integer): CONTROL_MESSAGE_IMAX. The actual
maximum timeout is described as a number of doublings of
CONTROL_MESSAGE_IMIN. 0 and 0xff are reserved and MUST NOT be
used.
C_T_EXP (unsigned 16-bit integer): CONTROL_MESSAGE_TIMER_EXPIRATIONS
. 0 and 0xffff are reserved and MUST NOT be used.
Note that the time values (SEED_SET_ENTRY_LIFETIME,
DATA_MESSAGE_IMIN, and CONTROL_MESSAGE_IMIN) in MPL are defined in
TUNIT milliseconds precision in MPL Parameter Configuration Options.
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.
For maximum interval size (*_IMAX), [RFC6206] defines them as
follows:
The maximum interval size, Imax, is described as a number of
doublings of the minimum interval size (the base-2 log(max/min)).
For example, a protocol might define Imax as 16. If the minimum
interval is 100 ms, then the amount of time specified by Imax is
100 ms * 65,536, i.e., 6,553.6 seconds or approximately 109
minutes.
Because minimum interval size in the MPL Parameter Configuration
Options is described as TUNIT millisecond precision, corresponding
maximum interval size is also in TUNIT precision. For example, if
TUNIT is 10 and C_IMIN is 50, the minimum interval size of the
trickle timer for control messages is 500ms. In this case, the
maximum interval size of the trickle timer is 32 seconds (500ms *
2^6) if C_IMAX is 6.
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.
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Clients MUST support multiple MPL Parameter Configuration Option, as
stated in section 2.
If a DHCPv6 client with an MPL forwarder configured by the MPL
Parameter Configuration Option is unable to receive a valid response
from a server within T2 of the last valid DHCPv6 message sent from
the server (if stateful) or twice the Information Refresh Time (if
stateless), it MUST suspend the MPL forwarders of the MPL domains
configured by the option. MPL forwarders configured by other methods
such as static configuration file MUST NOT be suspended.
Clients MUST ignore all MPL Parameter Configuration Options if the
options in a DHCPv6 message contains any invalid value (e.g., it uses
reserved all-0 or all-1 values in parameters). In this case, the
message is considered not received in MPL context and the condition
described in the previous paragraph applies.
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 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. Each MPL
domain is defined by an MPL Domain Address given by an MPL Parameter
Configuration Option. As defined in Section 2 of
[I-D.ietf-roll-trickle-mcast], an MPL Domain Address is an IPv6
multicast address associated to a set of MPL network interfaces in an
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.
Priority of other configurations such as manual configuration given
on a node is not defined in the document.
There MUST 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 MUST leave an MPL domain if it receives an updated and all-
valid MPL Parameter Configuration Options without a configuration for
the MPL domain, unless it has overriding manual configuration on the
MPL domain. In other words, if a node is configured to work as a MPL
Forwarder for a MPL domain regardless of DHCPv6 Options, the node MAY
stay on the MPL domain even if it receives an MPL Parameter
Configuration Option without 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 this 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 MUST ignore an incoming MPL Parameter Configuration Option.
Servers MUST support multiple MPL Parameter Configuration Option, as
stated in section 2.
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
This draft introduces dynamic update of MPL parameters. Because the
update process is not synchronized, nodes may have inconsistent
parameter sets.
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[RFC6206] section 6 describe various problems that happens if the
trickle timers do not match between communicating nodes. To keep the
timers synchronized, it is RECOMMENDED not to update the parameters
of an MPL domain too often. A reasonable update rate would be once
per expected information refresh time interval, such as T1 in
[RFC3315] or Information Refresh Time in [RFC4242].
Inconsistent parameter sets may reduce performance. On the other
hand, this situation will work as long as both new and old 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.
3. IANA Considerations
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 (http://www.iana.org/assignments/
dhcpv6-parameters).
4. Security Considerations
There are detailed discussion on security threats on DHCPv6 in
Section 23 of RFC3315 [RFC3315], Section 23 of RFC7227 [RFC7227], and
Section 13 of [I-D.ietf-roll-trickle-mcast].
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.
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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 to protect integrity between DHCPv6 servers and
clients 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, DHCPv6
packets SHOULD be filtered on the border router between the ROLL
network and the Internet, except for the packets between the ROLL
network and a remote DHCPv6 server or DHCPv6 relays configured to
manage the network.
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.
[RFC6206] Levis, P., Clausen, T., Hui, J., Gnawali, O., and J. Ko,
"The Trickle Algorithm", RFC 6206, DOI 10.17487/RFC6206,
March 2011, <http://www.rfc-editor.org/info/rfc6206>.
[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.
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[ZigBeeIP]
ZigBee Alliance, "ZigBee IP Specification", Mar 2014.
Appendix A. Update History (TO EDITORS: this section is intended to be
removed before this document becomes an RFC)
Updates on draft-ietf-roll-mpl-configuration-07 to draft-ietf-roll-
mpl-configuration-08:
o clarified when to leave (SHOULD->MUST)
o moved Trickle parameter considerations on appendix to operational
considerations
o even clarified some texts
Updates on draft-ietf-roll-mpl-configuration-06 to draft-ietf-roll-
mpl-configuration-07:
o clearly stated multiple option support is mandatory (#171)
o operational consideration now refers RFC6206 and some texts are
moved to section 2.2 (#171)
o added more per-section reference to I-D.ietf-roll-trickle-mcast
(#171)
o field 'Z' clarified (#171, #172)
o fixed other nits (#171)
o clarified use of TUNIT, *_IMIN, and *_IMAX with reference to
RFC6206 (#172)
Updates on draft-ietf-roll-mpl-configuration-05 to draft-ietf-roll-
mpl-configuration-06:
o added description on manual (external) configurations
Updates on draft-ietf-roll-mpl-configuration-04 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
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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
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.
Authors' Addresses
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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
Matthew Gillmore
Itron, Inc
2111 N Molter Rd.
Liberty Lake, WA 99019
USA
Email: matthew.gillmore@itron.com
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