Reducing Energy Consumption of Router Advertisements
RFC 7772

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Internet Engineering Task Force (IETF)                    A. Yourtchenko
Request for Comments: 7772                                         Cisco
BCP: 202                                                      L. Colitti
Category: Best Current Practice                                   Google
ISSN: 2070-1721                                            February 2016

          Reducing Energy Consumption of Router Advertisements

Abstract

   Frequent Router Advertisement messages can severely impact host power
   consumption.  This document recommends operational practices to avoid
   such impact.

Status of This Memo

   This memo documents an Internet Best Current Practice.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   BCPs is available in Section 2 of RFC 5741.

   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 (c) 2016 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
   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.

Yourtchenko & Colitti     Best Current Practice                 [Page 1]
RFC 7772             Reducing RA Energy Consumption        February 2016

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Problem Scenarios . . . . . . . . . . . . . . . . . . . . . .   2
     2.1.  Solicited Multicast RAs on Large Networks . . . . . . . .   2
     2.2.  Frequent Periodic Router Advertisements . . . . . . . . .   3
   3.  Consequences  . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Router Advertisement Frequency  . . . . . . . . . . . . . . .   3
   5.  Recommendations . . . . . . . . . . . . . . . . . . . . . . .   4
     5.1.  Network-Side Recommendations  . . . . . . . . . . . . . .   4
     5.2.  Device-Side Recommendations . . . . . . . . . . . . . . .   5
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   Routing information is communicated to IPv6 hosts by Router
   Advertisement (RA) messages [RFC4861].  If these messages are sent
   too frequently, they can severely impact power consumption on
   battery-powered hosts.

   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.  Problem Scenarios

2.1.  Solicited Multicast RAs on Large Networks

   On links with a large number of battery-powered devices, sending
   solicited multicast Router Advertisements can severely impact host
   power consumption.  This is because every time a device joins the
   network, all devices on the network receive a multicast Router
   Advertisement.  In the worst case, if devices are continually joining
   and leaving the network, and the network is large enough, then all
   devices on the network will receive solicited Router Advertisements
   at the maximum rate specified by Section 6.2.6 of [RFC4861], which is
   one every 3 seconds.

Yourtchenko & Colitti     Best Current Practice                 [Page 2]
RFC 7772             Reducing RA Energy Consumption        February 2016

2.2.  Frequent Periodic Router Advertisements

   Some networks send periodic multicast Router Advertisements very
   frequently (e.g., once every few seconds).  This may be due to a
   desire to minimize customer impact of network renumbering events,
   which in some large residential networks occur relatively frequently.
   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
   frequently in order to avoid leaving devices with non-functional IPv6
   configurations for extended periods of time.  Unfortunately, this has