draft-ietf-v6ops-reducing-ra-energy-consumption-03.txt		rfc7772.txt
	IPv6 Operations A. Yourtchenko		Internet Engineering Task Force (IETF) A. Yourtchenko
	Internet-Draft Cisco		Request for Comments: 7772 Cisco
	Intended status: Best Current Practice L. Colitti		BCP: 202 L. Colitti
	Expires: May 8, 2016 Google		Category: Best Current Practice Google
	November 5, 2015		ISSN: 2070-1721 February 2016
	Reducing energy consumption of Router Advertisements		Reducing Energy Consumption of Router Advertisements
	draft-ietf-v6ops-reducing-ra-energy-consumption-03
	Abstract		Abstract
	Frequent Router Advertisement messages can severely impact host power		Frequent Router Advertisement messages can severely impact host power
	consumption. This document recommends operational practices to avoid		consumption. This document recommends operational practices to avoid
	such impact.		such impact.
	Status of This Memo		Status of This Memo
	This Internet-Draft is submitted in full conformance with the		This memo documents an Internet Best Current Practice.
	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		This document is a product of the Internet Engineering Task Force
	and may be updated, replaced, or obsoleted by other documents at any		(IETF). It represents the consensus of the IETF community. It has
	time. It is inappropriate to use Internet-Drafts as reference		received public review and has been approved for publication by the
	material or to cite them other than as "work in progress."		Internet Engineering Steering Group (IESG). Further information on
			BCPs is available in Section 2 of RFC 5741.
	This Internet-Draft will expire on May 8, 2016.		Information about the current status of this document, any errata,
			and how to provide feedback on it may be obtained at
			http://www.rfc-editor.org/info/rfc7772.
	Copyright Notice		Copyright Notice
	Copyright (c) 2015 IETF Trust and the persons identified as the		Copyright (c) 2016 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents
	(http://trustee.ietf.org/license-info) in effect on the date of		(http://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	carefully, as they describe your rights and restrictions with respect		carefully, as they describe your rights and restrictions with respect
	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
	include Simplified BSD License text as described in Section 4.e of		include Simplified BSD License text as described in Section 4.e of
	the Trust Legal Provisions and are provided without warranty as		the Trust Legal Provisions and are provided without warranty as
	described in the Simplified BSD License.		described in the Simplified BSD License.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
	2. Problem scenarios . . . . . . . . . . . . . . . . . . . . . . 2		2. Problem Scenarios . . . . . . . . . . . . . . . . . . . . . . 2
	2.1. Solicited multicast RAs on large networks . . . . . . . . 2		2.1. Solicited Multicast RAs on Large Networks . . . . . . . . 2
	2.2. Frequent periodic Router Advertisements . . . . . . . . . 2		2.2. Frequent Periodic Router Advertisements . . . . . . . . . 3
	3. Consequences . . . . . . . . . . . . . . . . . . . . . . . . 3		3. Consequences . . . . . . . . . . . . . . . . . . . . . . . . 3
	4. Router Advertisement frequency . . . . . . . . . . . . . . . 3		4. Router Advertisement Frequency . . . . . . . . . . . . . . . 3
	5. Recommendations . . . . . . . . . . . . . . . . . . . . . . . 4		5. Recommendations . . . . . . . . . . . . . . . . . . . . . . . 4
	5.1. Network-side recommendations . . . . . . . . . . . . . . 4		5.1. Network-Side Recommendations . . . . . . . . . . . . . . 4
	5.2. Device-side recommendations . . . . . . . . . . . . . . . 5		5.2. Device-Side Recommendations . . . . . . . . . . . . . . . 5
	6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5		6. Security Considerations . . . . . . . . . . . . . . . . . . . 5
	7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5		7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
	8. Security Considerations . . . . . . . . . . . . . . . . . . . 5		7.1. Normative References . . . . . . . . . . . . . . . . . . 5
	9. Normative References . . . . . . . . . . . . . . . . . . . . 5		7.2. Informative References . . . . . . . . . . . . . . . . . 6
			Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 6
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
	1. Introduction		1. Introduction
	Routing information is communicated to IPv6 hosts by Router		Routing information is communicated to IPv6 hosts by Router
	Advertisement (RA) messages [RFC4861]. If these messages are too		Advertisement (RA) messages [RFC4861]. If these messages are sent
	frequent, they can severely impact power consumption on battery-		too frequently, they can severely impact power consumption on
	powered hosts.		battery-powered hosts.
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this		"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
	document are to be interpreted as described in [RFC2119].		document are to be interpreted as described in [RFC2119].
	2. Problem scenarios		2. Problem Scenarios
	2.1. Solicited multicast RAs on large networks		2.1. Solicited Multicast RAs on Large Networks
	On links with a large number of battery-powered devices, sending		On links with a large number of battery-powered devices, sending
	solicited Router Advertisements multicast can severely impact host		solicited multicast Router Advertisements can severely impact host
	power consumption. This is because every time a device joins the		power consumption. This is because every time a device joins the
	network, all devices on the network receive a multicast Router		network, all devices on the network receive a multicast Router
	Advertisement. In the worst case, if devices are continually joining		Advertisement. In the worst case, if devices are continually joining
	and leaving the network, and the network is large enough, then all		and leaving the network, and the network is large enough, then all
	devices on the network will receive solicited Router Advertisements		devices on the network will receive solicited Router Advertisements
	at the maximum rate specified by section 6.2.6 of [RFC4861], which is		at the maximum rate specified by Section 6.2.6 of [RFC4861], which is
	one every 3 seconds.		one every 3 seconds.
	2.2. Frequent periodic Router Advertisements		2.2. Frequent Periodic Router Advertisements
	Some networks send periodic multicast Router Advertisements very		Some networks send periodic multicast Router Advertisements very
	frequently (e.g., once every few seconds). This may be due to a		frequently (e.g., once every few seconds). This may be due to a
	desire to minimize customer impact of network renumbering events,		desire to minimize customer impact of network renumbering events,
	which in some large residential networks occur relatively frequently.		which in some large residential networks occur relatively frequently.
	In the presence of hosts that ignore RAs or even all IPv6 packets		In the presence of hosts that ignore RAs or even all IPv6 packets
	when in sleep mode, such networks may see a need to send RAs		when in sleep mode, such networks may see a need to send RAs
	frequently in order to avoid leaving devices with non-functional IPv6		frequently in order to avoid leaving devices with non-functional IPv6
	configurations for extended periods of time. Unfortunately, this has		configurations for extended periods of time. Unfortunately, this has
	severe impact on battery life.		severe impact on battery life.
	3. Consequences		3. Consequences
	Observed reactions to frequent Router Advertisement messages by		Observed effects of frequently sending Router Advertisement messages
	battery-powered devices include:		to battery-powered devices include:
	o Some hosts simply experience bad battery life on these networks		o Some hosts simply experience bad battery life on these networks
	and otherwise operate normally. This is frustrating for users of		and otherwise operate normally. This is frustrating for users of
	these networks.		these networks.
	o Some hosts react by dropping all Router Advertisement messages		o Some hosts react by dropping all Router Advertisement messages
	when in power saving mode on any network, e.g.,		when in power-saving mode on any network, e.g.,
	<https://code.google.com/p/android/issues/detail?id=32662>. This		<https://code.google.com/p/android/issues/detail?id=32662>. This
	causes devices to lose connectivity when in power-saving mode,		causes devices to lose connectivity when in power-saving mode,
	potentially disrupting background network communications, because		potentially disrupting background network communications, because
	the device is no longer able to send packets or acknowledge		the device is no longer able to send packets or acknowledge
	received traffic.		received traffic.
	o Some hosts react by dropping *all* IPv6 packets when in power		o Some hosts react by dropping *all* IPv6 packets when in power-
	saving mode, <http://www.gossamer-threads.com/lists/nsp/		saving mode, <http://www.gossamer-threads.com/lists/nsp/
	ipv6/54641>. This disrupts network communications.		ipv6/54641>. This disrupts network communications.
	Compounding the problem, when dealing with devices that drop Router		Compounding the problem, when dealing with devices that drop Router
	Advertisements when in power saving mode, some network administrators		Advertisements when in power saving mode, some network administrators
	work around the problem by sending RAs even more frequently. This		work around the problem by sending RAs even more frequently. This
	causes devices to engage in even more aggressive filtering.		causes devices to engage in even more aggressive filtering.
	4. Router Advertisement frequency		4. Router Advertisement Frequency
	The appropriate frequency of periodic RAs depends on how constrained		The appropriate frequency of periodic RAs depends on how constrained
	the network devices are.		the network devices are.
	o Laptop-class devices will likely experience no noticeable battery		o Laptop-class devices will likely experience no noticeable battery-
	life impact even if RAs are sent every few seconds.		life impact, even if RAs are sent every few seconds.
	o Tablets, phones, and watches experience it more noticeably. At		o Tablets, phones, and watches experience it more noticeably. At
	the time of writing, current-generation devices might consume on		the time of writing, current-generation devices might consume on
	the order of 5 mA when the main processor is asleep. Upon		the order of 5 mA when the main processor is asleep. Upon
	receiving a packet, they might consume on the order of 200 mA for		receiving a packet, they might consume on the order of 200 mA for
	250ms, as the packet causes the main processor to wake up, process		250 ms, as the packet causes the main processor to wake up,
	the RA, attend to other pending tasks, and then go back to sleep		process the RA, attend to other pending tasks, and then go back to
	again. Thus, on such devices the cost of receiving one RA will be		sleep. Thus, on such devices, the cost of receiving one RA will
	approximately 0.014mAh.		be approximately 0.014 mAh.
	In order to limit the amount of power used to receive Router		In order to limit the amount of power used to receive Router
	Advertisements to, say, 2% of idle power (i.e., to impact idle		Advertisements to, say, 2% of idle power (i.e., to impact idle
	battery life by no more than 2%), the average power budget for		battery life by no more than 2%), the average power budget for
	receiving RAs must be no more than 0.1mA, or approximately 7 RAs		receiving RAs must be no more than 0.1 mA, or approximately 7 RAs
	per hour. Due to background multicast loss and the tendency of		per hour. Due to background multicast loss and the tendency of
	current devices to rate-limit multicast when asleep, many of these		current devices to rate-limit multicast when asleep, many of these
	RAs might not reach the device. Thus the minimum lifetimes for RA		RAs might not reach the device. Thus, the minimum lifetimes for
	configuration parameters such as default router lifetime might		RA configuration parameters such as default router lifetime might
	reasonably be 5-10 times the RA period, or roughly 45-90 minutes.		reasonably be 5-10 times the RA period, or roughly 45-90 minutes.
	An idle time impact of 2% relative to measured idle current is		An impact of 2% relative to measured idle current is negligible,
	negligible, since on this sort of device average power consumption		since on this sort of device average power consumption is
	is typically much higher than idle power consumption.		typically much higher than idle power consumption.
	o Specialized devices in non-general-purpose networks such as sensor		o Specialized devices in non-general-purpose networks such as sensor
	networks might have tighter requirements. In these environments,		networks might have tighter requirements. In these environments,
	even longer RA intervals might be appropriate.		even longer RA intervals might be appropriate.
	5. Recommendations		5. Recommendations
	5.1. Network-side recommendations		5.1. Network-Side Recommendations
	1. Router manufacturers SHOULD allow network administrators to		1. Router manufacturers SHOULD allow network administrators to
	configure the routers to respond to Router Solicitations with		configure the routers to respond to Router Solicitations with
	unicast Router Advertisements if:		unicast Router Advertisements if:
	* The Router Solicitation's source address is not the		* The Router Solicitation's source address is not the
	unspecified address, and:		unspecified address, and:
	* The solicitation contains a valid Source Link-Layer Address		* The solicitation contains a valid Source Link-Layer Address
	option.		option.
	2. Administrators of networks that serve large numbers (tens or		2. Administrators of networks that serve large numbers (tens or
	hundreds) of battery-powered devices SHOULD enable this		hundreds) of battery-powered devices SHOULD enable this behavior.
	behaviour.
	3. Networks that serve battery-powered devices SHOULD NOT send		3. Networks that serve battery-powered devices SHOULD NOT send
	multicast RAs too frequently (see section Section 4) unless the		multicast RAs too frequently (see Section 4) unless the
	information in the RA packet has substantially changed. If there		information in the RA packet has substantially changed. If there
	is a desire to ensure that hosts pick up configuration changes		is a desire to ensure that hosts pick up configuration changes
	quickly, those networks MAY send frequent Router Advertisements		quickly, those networks MAY send frequent Router Advertisements
	for a limited period of time (e.g., not more than one minute)		for a limited period of time (e.g., not more than one minute)
	immediately after a configuration change.		immediately after a configuration change.
	No protocol changes are required. Responding to Router Solicitations		No protocol changes are required. Responding to Router Solicitations
	with unicast Router Advertisements is already allowed by section		with unicast Router Advertisements is already allowed by Section
	6.2.6 of [RFC4861], and Router Advertisement intervals are already		6.2.6 of [RFC4861], and Router Advertisement intervals are already
	configurable by the administrator to a wide range of values.		configurable by the administrator to a wide range of values.
	5.2. Device-side recommendations		5.2. Device-Side Recommendations
	1. Maintaining IPv6 connectivity requires that hosts be able to		1. Maintaining IPv6 connectivity requires that hosts be able to
	receive periodic multicast RAs [RFC4861] Therefore, hosts that		receive periodic multicast RAs [RFC4861]. Therefore, hosts that
	process unicast packets sent while they are asleep MUST also		process unicast packets sent while they are asleep MUST also
	process multicast RAs sent while they are asleep. Battery-		process multicast RAs sent while they are asleep. Battery-
	powered hosts MAY rate-limit identical RAs if they are sent too		powered hosts MAY rate-limit identical RAs if they are sent too
	frequently.		frequently.
	2. Battery-powered devices that do not intend to maintain IPv6		2. Battery-powered devices that do not intend to maintain IPv6
	connectivity while asleep SHOULD either disconnect from the		connectivity while asleep SHOULD either disconnect from the
	network, abandoning all IPv6 configuration on that network, or		network, abandoning all IPv6 configuration on that network, or
	perform DNAv6 procedures [RFC6059] when waking up.		perform Detecting Network Attachment in IPv6 (DNAv6) procedures
			[RFC6059] when waking up.
	6. Acknowledgements
	The authors wish to thank Steven Barth, Frank Bulk, David Farmer,
	Igor Gashinsky, Ray Hunter, Erik Kline, Erik Nordmark, Alexandru
	Petrescu, Libor Polcak, Mark Smith, Jinmei Tatuya and James Woodyatt
	for feedback and helpful suggestions.
	7. IANA Considerations
	None.
	8. Security Considerations		6. Security Considerations
	Misconfigured or malicious hosts sending rogue Router Advertisements		Misconfigured or malicious hosts sending rogue Router Advertisements
	[RFC6104] can also severely impact power consumption on battery-		[RFC6104] can also severely impact power consumption on battery-
	powered hosts if they send a significant number of such messages.		powered hosts if they send a significant number of such messages.
	Any IPv6 network where there is potential for misconfigured or		Any IPv6 network where there is potential for misconfigured or
	malicious hosts should take appropriate countermeasures to mitigate		malicious hosts should take appropriate countermeasures to mitigate
	the problem.		the problem.
	9. Normative References		7. References
			7.1. Normative References
	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate		[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
	Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/		Requirement Levels", BCP 14, RFC 2119,
	RFC2119, March 1997,		DOI 10.17487/RFC2119, March 1997,
	<http://www.rfc-editor.org/info/rfc2119>.		<http://www.rfc-editor.org/info/rfc2119>.
	[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,		[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
	"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,		"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
	DOI 10.17487/RFC4861, September 2007,		DOI 10.17487/RFC4861, September 2007,
	<http://www.rfc-editor.org/info/rfc4861>.		<http://www.rfc-editor.org/info/rfc4861>.
	[RFC6059] Krishnan, S. and G. Daley, "Simple Procedures for		[RFC6059] Krishnan, S. and G. Daley, "Simple Procedures for
	Detecting Network Attachment in IPv6", RFC 6059, DOI		Detecting Network Attachment in IPv6", RFC 6059,
	10.17487/RFC6059, November 2010,		DOI 10.17487/RFC6059, November 2010,
	<http://www.rfc-editor.org/info/rfc6059>.		<http://www.rfc-editor.org/info/rfc6059>.
			7.2. Informative References
			[RFC6104] Chown, T. and S. Venaas, "Rogue IPv6 Router Advertisement
			Problem Statement", RFC 6104, DOI 10.17487/RFC6104,
			February 2011, <http://www.rfc-editor.org/info/rfc6104>.
			Acknowledgements
			The authors wish to thank Steven Barth, Frank Bulk, David Farmer,
			Igor Gashinsky, Ray Hunter, Erik Kline, Erik Nordmark, Alexandru
			Petrescu, Libor Polcak, Mark Smith, Jinmei Tatuya, and James Woodyatt
			for feedback and helpful suggestions.
	Authors' Addresses		Authors' Addresses
	Andrew Yourtchenko		Andrew Yourtchenko
	Cisco		Cisco
	7a de Kleetlaan		7a de Kleetlaan
	Diegem, 1831		Diegem, 1831
	Belgium		Belgium
	Phone: +32 2 704 5494		Phone: +32 2 704 5494
	Email: ayourtch@cisco.com		Email: ayourtch@cisco.com
	Lorenzo Colitti		Lorenzo Colitti
	Google		Google
	Roppongi 6-10-1		Roppongi 6-10-1
	Minato, Tokyo 106-6126		Minato, Tokyo 106-6126
	JP		Japan
	Email: lorenzo@google.com		Email: lorenzo@google.com
End of changes. 38 change blocks.
	82 lines changed or deleted		82 lines changed or added
This html diff was produced by rfcdiff 1.42. The latest version is available from http://tools.ietf.org/tools/rfcdiff/