roll Y. Doi Internet-Draft TOSHIBA Corporation Intended status: Standards Track M. Gillmore Expires: January 3, 2015 Itron, Inc July 2, 2014 MPL Parameter Configuration Option for DHCPv6 draft-ietf-roll-mpl-parameter-configuration-01 Abstract This draft defines a way to configure MPL parameter set via 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 parameter 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 Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any 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 January 3, 2015. Copyright Notice Copyright (c) 2014 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 (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must Doi & Gillmore Expires January 3, 2015 [Page 1] Internet-Draft MPL Conf. for DHCPv6 July 2014 include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. MPL Parameter Configuration Option . . . . . . . . . . . . . 2 2.1. Unsigned Short Floating Point . . . . . . . . . . . . . . 3 2.2. MPL Parameter Configuration Option Format . . . . . . . . 4 2.3. DHCPv6 Client Behavior . . . . . . . . . . . . . . . . . 6 2.4. MPL Forwarder Behavior . . . . . . . . . . . . . . . . . 6 2.5. DHCPv6 Server Behavior . . . . . . . . . . . . . . . . . 7 2.6. DHCPv6 Relay Behavior . . . . . . . . . . . . . . . . . . 7 2.7. Operational Considerations . . . . . . . . . . . . . . . 7 3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 4. Security Considerations . . . . . . . . . . . . . . . . . . . 7 5. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 5.1. Normative References . . . . . . . . . . . . . . . . . . 8 5.2. Non-Normative 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 network i.e. wireless mesh networks. MPL has a set of parameters to control its behavior and tradeoff 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 draft section 5.4, each parameter in the set should be same for all nodes within an MPL domain. And the MPL draft 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 set shall be considered as a part of network parameters (nodes in an MPL domain should use an identical parameter set). This document is to define the way to distribute parameter sets for MPL forwarders as a simple DHCPv6 [RFC3315] option. 2. MPL Parameter Configuration Option Doi & Gillmore Expires January 3, 2015 [Page 2] Internet-Draft MPL Conf. for DHCPv6 July 2014 Per MPL domain, there are 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 from a DHCP server. 2.1. Unsigned Short Floating Point MPL has many timer parameters. Expected range of the timers depends on the network topology or MAC/PHY nature. To accommodate wide range of timer values efficiently, the MPL Parameter Configuration Option uses base-10 unsigned short floating point number with 3-bit exponent and 13-bit significand defined as follows (exp. stands for exponent). 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | exp.| significand | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The represented value is (significand) * 10^(exp.). The minimum exponent is 0 (binary 000) and the maximum is 6 (binary 110). exp=7 (binary 111) is reserved for future use. The minimum significand is 0 (all 0) and the maximum is 8191 (all 1). Doi & Gillmore Expires January 3, 2015 [Page 3] Internet-Draft MPL Conf. for DHCPv6 July 2014 Unlike IEEE754 half precision floating point (binary16), there is no sign bit (no negative value for a timer), exponent is not biased (no fractional value for a timer), no implicit leading 1 in siginificand, and base is 10. Therefore, there could be more than one representation for a value. Followings are examples of common timer values represented by unit of millisecond. One second (1,000 milliseconds): exp = 3, significand = 1, 0x6001. One minute (60,000 milliseconds): exp = 4, significand = 6, 0x8006. One hour (3,600,000 milliseconds): exp = 5, significand = 36, 0xa024. One day (86,400,000 milliseconds): exp = 5, significand = 864, 0xa360 Maximum timer length represented by an unsigned short floating point with millisecond precision is 8191 * 10^6 milliseconds (13 weeks 3 days 19 hours 16 minutes 40 seconds). With exponent and significand, an unsigned short floating point (usfp) can be encoded as follows. usfp = (exponent << 13)|(0x1fff & significand); 2.2. 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. Short floating point format is used to describe wide range of timer values. 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 | C_K | Z2 | DM_K | SE_LIFETIME | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | DM_IMIN | DM_IMAX | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | DM_T_EXP | C_IMIN | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | C_IMAX | C_T_EXP | Doi & Gillmore Expires January 3, 2015 [Page 4] Internet-Draft MPL Conf. for DHCPv6 July 2014 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ (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 Z (1 bit) Reserved. Should be 0. C_K (5 bits): CONTROL_MESSAGE_K. Z2 (3 bits) Reserved. Should be all 0. DM_K (5 bits): DATA_MESSAGE_K. SE_LIFETIME: SEED_SET_ENTRY_LIFETIME. The unit is millisecond and the type is unsigned short floating point. DM_IMIN: DATA_MESSAGE_IMIN. The unit is millisecond and the type is unsigned short floating point. DM_IMAX: DATA_MESSAGE_IMAX. The unit is millisecond and the type is unsigned short floating point. DM_T_EXP: DATA_MESSAGE_TIMER_EXPIRATIONS. The unit is millisecond and the type is unsigned short floating point. C_IMIN: CONTROL_MESSAGE_IMIN. The unit is millisecond and the type is unsigned short floating point. C_IMAX: CONTROL_MESSAGE_IMAX. The unit is millisecond and the type is unsigned short floating point. C_T_EXP: CONTROL_MESSAGE_TIMER_EXPIRATIONS. The unit is millisecond and the type is unsigned short floating point. Doi & Gillmore Expires January 3, 2015 [Page 5] Internet-Draft MPL Conf. for DHCPv6 July 2014 2.3. DHCPv6 Client Behavior Clients MAY request MPL Parameter Configuration Option, as described in RFC3315 [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 Option Request Option. Clients MUST discard MPL Parameter Configuration Option if it is invalid (i.e. it sets reserved bits or it has timers with reserved exp=7 in Unsigned Short Floating Point). 2.4. MPL Forwarder Behavior If a DHCPv6 client requests and receives MPL Parameter Configuration Option, the node MAY join the MPL domain given by the option and act as an MPL forwarder. Each joining node SHOULD configure its MPL forwarder with the given parameter set for the MPL domain. The priority of MPL Parameter Configuration applied for an MPL Domain is as follows (high to low). o Specific MPL Parameter Configuration to the MPL Domain (optlen=32) o Wildcard MPL Parameter Configuration (optlen=16) o Default configuration given in the MPL specification. There SHALL be no more than one MPL Parameter Configuration Option for a MPL domain or the wildcard. Thus, the order of DHCPv6 options in the packet has no effect on precedence. A node MAY leave from 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 parameter 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 forwarders updated. To reduce periodical update traffic a node may try to use very long interval between updates. In the case, reconfigure shall be used to keep forwarder parameter sets synchronized. For stateless DHCPv6, [I-D.jiang-dhc-stateless-reconfiguration] may be used (if approved). Doi & Gillmore Expires January 3, 2015 [Page 6] Internet-Draft MPL Conf. for DHCPv6 July 2014 2.5. DHCPv6 Server Behavior Sections 17.2.2 and 18.2 of RFC3315 [RFC3315] govern server operation in regards to option assignment. As a convenience to the reader, we mention here that the server will send MPL Parameter Configuration Option only if configured with specific value for MPL Parameter Configuration Option and the client requested it. Servers SHALL ignore incoming MPL Parameter Configuration Option. 2.6. 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. 2.7. Operational Considerations A parameter set for an MPL domain SHOULD NOT updated more often than two times of expected refresh interval. If a node with MPL forwarder configured by MPL Parameter configuration Option failed to refresh the option for two times of information refresh time, it SHALL suspend the MPL forwarders of MPL domains configured by the option. MPL forwarders configured by other methods such as static configuration file SHALL NOT be suspended. 3. IANA Considerations A DHCPv6 option code for MPL Parameter Configuration Option needs to be assigned from IANA. 4. Security Considerations A forged option may cause excessive layer-2 broadcasting. Implementations should set reasonable bounds for each parameter. For example, not too high K, not too low IMIN, etc. These may be implementation dependent or may be derived from MAC/PHY specifications. DHCP server or the network itself shall be trusted by some means including network access control or DHCP authentications. Doi & Gillmore Expires January 3, 2015 [Page 7] Internet-Draft MPL Conf. for DHCPv6 July 2014 5. References 5.1. Normative References [I-D.ietf-roll-trickle-mcast] Hui, J. and R. Kelsey, "Multicast Forwarding Using Trickle", draft-ietf-roll-trickle-mcast-07 (work in progress), Feburary 2014. [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. 5.2. Non-Normative References [I-D.ietf-dhc-option-guidelines] Hankins, D., Mrugalski, T., Siodelski, M., Jiang, S., and S. Krishnan, "Guidelines for Creating New DHCPv6 Options", draft-ietf-dhc-option-guidelines-17 (work in progress), January 2014. [I-D.jiang-dhc-stateless-reconfiguration] Jiang, S. and B. Liu, "Stateless Reconfiguration in Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", draft-jiang-dhc-stateless-reconfiguration-01 (work in progress), February 2014. Appendix A. Update History Updates on draft-doi-roll-mpl-configuration-05 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. Doi & Gillmore Expires January 3, 2015 [Page 8] Internet-Draft MPL Conf. for DHCPv6 July 2014 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 set. Inconsistent parameter may reduce performance. On the other hand, it shall work as long as both parameter set are reasonable parameter set for a given communication load. As motivations for parameter update are update on 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 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 Matthew Gillmore Itron, Inc 2111 N Molter Rd. Liberty Lake, WA 99019 USA Email: matthew.gillmore@itron.com Doi & Gillmore Expires January 3, 2015 [Page 9]