draft-ietf-v6ops-reducing-ra-energy-consumption-01.txt   draft-ietf-v6ops-reducing-ra-energy-consumption-02.txt 
IPv6 Operations A. Yourtchenko IPv6 Operations A. Yourtchenko
Internet-Draft Cisco Internet-Draft Cisco
Intended status: Best Current Practice L. Colitti Intended status: Best Current Practice L. Colitti
Expires: March 10, 2016 Google Expires: April 4, 2016 Google
September 7, 2015 October 2, 2015
Reducing energy consumption of Router Advertisements Reducing energy consumption of Router Advertisements
draft-ietf-v6ops-reducing-ra-energy-consumption-01 draft-ietf-v6ops-reducing-ra-energy-consumption-02
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 Internet-Draft is submitted in full conformance with the
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on March 10, 2016. This Internet-Draft will expire on April 4, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2015 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
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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. Recommendations . . . . . . . . . . . . . . . . . . . . . . . 3 4. Router Advertisement frequency . . . . . . . . . . . . . . . 3
4.1. Network-side recommendations . . . . . . . . . . . . . . 3 5. Recommendations . . . . . . . . . . . . . . . . . . . . . . . 4
4.2. Device-side recommendations . . . . . . . . . . . . . . . 4 5.1. Network-side recommendations . . . . . . . . . . . . . . 4
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4 5.2. Device-side recommendations . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
7. Security Considerations . . . . . . . . . . . . . . . . . . . 4 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 4 8. Security Considerations . . . . . . . . . . . . . . . . . . . 5
8.1. Normative References . . . . . . . . . . . . . . . . . . 4 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
8.2. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 5 9.1. Normative References . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5 9.2. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 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 too
frequent, they can severely impact power consumption on battery- frequent, they can severely impact power consumption on battery-
powered hosts. 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
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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, [2]. This disrupts network communications. saving mode, [2]. 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. Recommendations 4. Router Advertisement frequency
4.1. Network-side recommendations The appropriate frequency of periodic RAs depends on how constrained
the network devices are.
o Laptop-class devices will likely experience no noticeable battery
life impact even if RAs are sent every few seconds.
o Tablets, phones, and watches experience it more noticeably. At
the time of writing, current-generation devices might consume on
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
250ms, as the packet causes the main processor to wake up, process
the RA, attend to other pending tasks, and then go back to sleep
again. Thus, on such devices the cost of receiving one RA will be
approximately 0.014mAh.
In order to limit the amount of power used to receive Router
Advertisements to, say, 2% of idle power (i.e., to impact idle
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
per hour. Due to background multicast loss and the tendency of
current devices to rate-limit multicast when asleep, many of these
RAs might not reach the device. Thus the minimum lifetimes for RA
configuration parameters such as default router lifetime might
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
negligible, since on this sort of device average power consumption
is typically much higher than idle power consumption.
o Specialized devices in non-general-purpose networks such as sensor
networks might have tighter requirements. In these environments,
even longer RA intervals might be appropriate.
5. 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
behaviour. 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 (e.g., more than one every 5-10 multicast RAs too frequently (see section Section 4) unless the
minutes for current battery-powered devices) 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.
4.2. Device-side recommendations 5.2. Device-side recommendations
1. Mobile devices that intend to maintain IPv6 connectivity while 1. Mobile devices that intend to maintain IPv6 connectivity while
asleep MUST NOT ignore RAs while asleep. asleep MUST NOT ignore RAs while asleep.
2. Mobile devices that do not intend to maintain IPv6 connectivity 2. Mobile devices that do not intend to maintain IPv6 connectivity
while asleep SHOULD disconnect from the IPv6 network and SHOULD while asleep SHOULD disconnect from the IPv6 network and SHOULD
reconnect to the network (including performing any DNAv6 reconnect to the network (including performing any DNAv6
procedures [RFC6059], sending Router Solicitations and performing procedures [RFC6059], sending Router Solicitations and performing
Duplicate Address Detection) when waking up. Duplicate Address Detection) when waking up.
5. Acknowledgements 6. Acknowledgements
The authors wish to thank Steven Barth, Erik Kline, Erik Nordmark, The authors wish to thank Steven Barth, Frank Bulk, David Farmer, Ray
Alexandru Petrescu, Mark Smith, and Jinmei Tatuya for feedback and Hunter, Erik Kline, Erik Nordmark, Alexandru Petrescu, Libor Polcak,
helpful suggestions. Mark Smith, and Jinmei Tatuya for feedback and helpful suggestions.
6. IANA Considerations 7. IANA Considerations
None. None.
7. Security Considerations 8. Security Considerations
None. Misconfigured or malicious hosts sending rogue Router Advertisements
[RFC6104] can also severely impact power consumption on battery-
powered hosts if they send a significant number of such messages.
Any IPv6 network where there is potential for misconfigured or
malicious hosts should take appropriate countermeasures to mitigate
the problem.
8. References 9. References
8.1. Normative References 9.1. 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, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[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,
September 2007. September 2007.
[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 10 Detecting Network Attachment in IPv6", RFC 6059, DOI 10
.17487/RFC6059, November 2010, .17487/RFC6059, November 2010,
<http://www.rfc-editor.org/info/rfc6059>. <http://www.rfc-editor.org/info/rfc6059>.
8.2. URIs 9.2. URIs
[1] https://code.google.com/p/android/issues/detail?id=32662 [1] https://code.google.com/p/android/issues/detail?id=32662
[2] http://www.gossamer-threads.com/lists/nsp/ipv6/54641 [2] http://www.gossamer-threads.com/lists/nsp/ipv6/54641
Authors' Addresses Authors' Addresses
Andrew Yourtchenko Andrew Yourtchenko
Cisco Cisco
7a de Kleetlaan 7a de Kleetlaan
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