Packet-Loss Resiliency for Router Solicitations
RFC 7559

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Internet Engineering Task Force (IETF)                       S. Krishnan
Request for Comments: 7559                                      Ericsson
Updates: 4861                                                  D. Anipko
Category: Standards Track                                   Unaffiliated
ISSN: 2070-1721                                                D. Thaler
                                                               Microsoft
                                                                May 2015

            Packet-Loss Resiliency for Router Solicitations

Abstract

   When an interface on a host is initialized, the host transmits Router
   Solicitations in order to minimize the amount of time it needs to
   wait until the next unsolicited multicast Router Advertisement is
   received.  In certain scenarios, these Router Solicitations
   transmitted by the host might be lost.  This document specifies a
   mechanism for hosts to cope with the loss of the initial Router
   Solicitations.

Status of This Memo

   This is an Internet Standards Track document.

   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
   Internet Standards 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/rfc7559.

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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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Conventions Used in This Document . . . . . . . . . . . .   3
   2.  Proposed Algorithm  . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Stopping the Retransmissions  . . . . . . . . . . . . . .   3
   3.  Configuring the Use of Retransmissions  . . . . . . . . . . .   4
   4.  Known Limitations . . . . . . . . . . . . . . . . . . . . . .   4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   As specified in [RFC4861], when an interface on a host is
   initialized, in order to obtain Router Advertisements quickly, a host
   transmits up to MAX_RTR_SOLICITATIONS (3) Router Solicitation (RS)
   messages, each separated by at least RTR_SOLICITATION_INTERVAL (4)
   seconds.  In certain scenarios, these Router Solicitations
   transmitted by the host might be lost.  For example, the host is
   connected to a bridged residential gateway over Ethernet or Wi-Fi.
   LAN connectivity is achieved at interface initialization, but the
   upstream WAN connectivity is not active yet.  In this case, the host
   just gives up after the initial RS retransmits.

   Once the initial RSs are lost, the host gives up and assumes that
   there are no routers on the link as specified in Section 6.3.7 of
   [RFC4861].  The host will not have any form of Internet connectivity
   until the next unsolicited multicast Router Advertisement is
   received.  These Router Advertisements are transmitted at most

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   MaxRtrAdvInterval seconds apart (maximum value 1800 seconds).  Thus,
   in the worst-case scenario a host would be without any connectivity
   for 30 minutes.  This delay may be unacceptable in some scenarios.

1.1.  Conventions Used in This Document

   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.  Proposed Algorithm