IPv6 Operations A. Yourtchenko Internet-Draft cisco Intended status: Best Current Practice L. Colitti Expires: January 7, 2016 Google July 6, 2015 Sending Solicited RAs Unicast draft-yc-v6ops-solicited-ra-unicast-00 Abstract On links with a large number of mobile devices, sending Solicited Router Advertisement as multicast packets can severely impact host power consumption. This document recommends that on such network, RAs be sent unicast. 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 7, 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 (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 Expires January 7, 2016 [Page 1] Internet-Draft Sending Solicited RAs Unicast July 2015 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Consequences . . . . . . . . . . . . . . . . . . . . . . . . 2 3. Recommendations . . . . . . . . . . . . . . . . . . . . . . . 3 4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 3 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3 6. Security Considerations . . . . . . . . . . . . . . . . . . . 3 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 3 7.1. Normative References . . . . . . . . . . . . . . . . . . 3 7.2. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction 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]. On links with a large number of mobile devices, sending solicited Router Advertisements as multicast packets 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. 2. Consequences Observed host reactions to this include: o Some hosts simply experience bad battery life on these networks and otherwise operate normally. This is frustrating for users of these networks. o Some hosts react by dropping all Router Advertisement packets when in power saving mode on any network, e.g., [1]. This causes devices to lose connectivity when in power-saving mode, potentially disrupting background network communications, because the device is no longer able to send packets or acknowledge received traffic. o Some hosts react by dropping *all* IPv6 packets when in power saving mode, [2]. This disrupts network communications. Yourtchenko & Colitti Expires January 7, 2016 [Page 2] Internet-Draft Sending Solicited RAs Unicast July 2015 Compounding the problem, when dealing with devices that drop Router Advertisements when in power saving mode, some network administrators work around the problem by sending RAs even more frequently. This causes devices to engage in even more aggressive filtering. 3. Recommendations Router manufacturers SHOULD allow network administrators to configure the routers to respond to Router Solicitations with unicast Router Advertisements. Networks that serve large numbers (tens or hundreds) of mobile devices SHOULD enable this behaviour. No protocol changes are required, since responding to Router Solicitations with unicast Router Advertisements is already allowed by section 6.2.4 of [RFC4861]. 4. Acknowledgements 5. IANA Considerations None. 6. Security Considerations Not discussed in -00. 7. References 7.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, September 2007. 7.2. URIs [1] https://code.google.com/p/android/issues/detail?id=32662 [2] http://www.gossamer-threads.com/lists/nsp/ipv6/54641 Yourtchenko & Colitti Expires January 7, 2016 [Page 3] Internet-Draft Sending Solicited RAs Unicast July 2015 Authors' Addresses Andrew Yourtchenko cisco 7a de Kleetlaan Diegem, 1831 Belgium Phone: +32 2 704 5494 Email: ayourtch@cisco.com Lorenzo Colitti Google Roppongi 6-10-1 Minato, Tokyo 106-6126 JP Email: lorenzo@google.com Yourtchenko & Colitti Expires January 7, 2016 [Page 4]