IPv6 Maintenance
Internet Engineering Task Force (IETF)                       S. Krishnan
Request for Comments: 8319                                        Kaloom
Updates: 4861 (if approved)                                                J. Korhonen
Intended status:
Category: Standards Track                                Broadcom
Expires: June 1, 2018                       Nordic Semiconductor ASA
ISSN: 2070-1721                                           S. Chakrabarti
                                                             E. Nordmark
                                                         Arista Networks
                                                          A. Yourtchenko
                                                       November 28, 2017
                                                           February 2018

        Support for adjustable maximum router lifetimes per-link
                        draft-ietf-6man-maxra-04 Adjustable Maximum Router Lifetimes per Link


   The IPv6 Neighbor Discovery protocol specifies the maximum time
   allowed between sending unsolicited multicast Router Advertisements
   (RAs) from a router interface as well as the maximum router lifetime.
   It also allows the limits to be overridden by link-layer documents that are
   documents. to the link layer.  This document allows for overriding
   these values on a per-link basis.

   This document specifies updates to the IPv6 Neighbor Discovery
   Protocol (RFC 4861) to increase the maximum time allowed between
   sending unsolicited multicast RAs from a router interface as well as
   to increase the maximum router lifetime.

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 an Internet Standards Track document.

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   This Internet-Draft will expire on June 1, 2018.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Relationship between AdvDefaultLifetime and MaxRtrAdvInterval   3
   4.  Updates to RFC4861 RFC 4861 . . . . . . . . . . . . . . . . . . . . .   4
   5.  Host Behavior . . . . . . . . . . . . . . . . . . . . . . . .   4   5
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   4   5
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4   5
   8.  Acknowledgements  References  . . . . . . . . . . . . . . . . . . . . . .   4
   9.  References . . .   5
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     8.2.  Informative References  . . . .   5
     9.1.  Normative References . . . . . . . . . . . . .   6
   Acknowledgements  . . . . .   5
     9.2.  Informative References . . . . . . . . . . . . . . . . .   5 . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5   7

1.  Introduction

   IPv6 Neighbor Discovery relies on IP multicast based on the
   expectation that multicast makes efficient use of available bandwidth
   and avoids generating interrupts in the network nodes.  On some
   datalink layers data
   link layers, multicast may not be natively supported.  On such links,
   any possible reduction of multicast traffic will be highly
   beneficial.  Unfortunately, due to the fixed protocol constants
   specified in [RFC4861], it is difficult to relax the multicast timers
   for neighbor discovery. Neighbor Discovery.  There are already clarifications specific to
   the link technology specific
   clarifications describing about how to tune the Neighbor Discovery Protocol
   (NDP) constants for certain systems with in order to reduce excess NDP
   traffic. e.g.  [RFC6459][RFC7066]  For example, [RFC6459] and [RFC7066] contain such
   clarifications for 3GPP cellular links.

   This document specifies updates to the IPv6 Neighbor Discovery
   Protocol [RFC4861] for increasing the to increase the maximum time allowed between
   sending unsolicited multicast Router Advertisements (RA) RAs from a router interface as well as for
   to increase the maximum router lifetime.

2.  Terminology  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "OPTIONAL" in this document are to be interpreted as described in [RFC2119].
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

3.  Relationship between AdvDefaultLifetime and MaxRtrAdvInterval

   MaxRtrAdvInterval is an upper bound on the time between which two
   successive Router Advertisement messages are sent.  Therefore  Therefore, one
   might reason about the relationship between these two values in terms
   of a ratio K=AdvDefaultLifetime/MaxRtrAdvInterval, K = AdvDefaultLifetime / MaxRtrAdvInterval, which
   expresses how many Router Advertisements will be are guaranteed to be sent
   before the router lifetime expires.

   Assuming unicast Solicited Router Advertisements or a perfectly
   stable network, on a theoretically perfect link with no losses, it
   would have been be sufficient to have K just above 1 - 1, so that the sent Router
   Advertisement refreshes the router entry just before it expires.  On
   the real links which that allow for some loss, one would need to use K>2 K > 2
   in order to minimize the chances of a single router
   advertisement Router Advertisement
   loss causing a loss of the router entry.

   The exact calculation will depend on the packet loss probability.  An
   example: if we take a ballpark value of 1% probability of a packet
   loss, then K=2 K = 2 will give 0.01% percent chance of an outage due to a packet
   loss, K=3 K = 3 will give 0.0001% chance of an outage, and so forth.  To
   reverse the numbers, with these parameters, K~=1 K ~= 1 gives 99%
   reliability, K~=2 K ~= 2 gives 99.99% reliability, and K~=3 K ~= 3 gives
   99.9999% reliability - the latter -- which should be good enough for a lot of

   In a network with higher packet loss probabilities or if the higher
   reliability is desired, the K might be chosen to be even higher.  On
   the other hand, some of the data link layers provide reliable
   delivery at layer 2 - Layer 2, so there one might even consider using the
   "theoretical" value of K just above 1.  Since the choice of these two
   parameters does not impact interoperability per se, this document
   does not impose any specific constraints on their values other than
   providing the guidelines in this section, therefore section.  Therefore, each individual
   link can optimize accordingly according to its use case.


   Also, AdvDefaultLifetime MUST be set to a value greater than or equal
   to the selected MaxRtrAdvInterval.  Otherwise, a router lifetime is
   guaranteed to expire before the new Router Advertisement has a chance
   to be sent, thereby creating an outage.

4.  Updates to RFC4861 RFC 4861

   This document updates Section Sections 4.2 and Section 6.2.1. 6.2.1 of [RFC4861] to
   update change
   the following router configuration variables.

   In Section 4.2, inside the paragraph that defines Router Lifetime,
   change 9000 to 65535 seconds.

   In Section 6.2.1, inside the paragraph that defines
   MaxRtrAdvInterval, change 1800 to 65535 seconds.

   In Section 6.2.1, inside the paragraph that defines
   AdvDefaultLifetime, change 9000 to 65535 seconds.

   As explained in Section 3, the probability of packet loss must be
   considered when choosing the relationship between MaxRtrAdvInterval
   and AdvDefaultLifetime must be chosen to take into account the
   probability of packet loss. AdvDefaultLifetime.

5.  Host Behavior

   Legacy hosts on a link with updated routers may have issues with a
   Router Lifetime of more than 9000 seconds.  In the few
   implementations we have tested with general purpose general-purpose operating
   systems, there does not seem to be any issues issue with setting this field
   to more than 9000, but there might be implementations that
   incorrectly reject such RAs (since RFC4861 RFC 4861 requires receivers to
   handle any value)
   reject such RAs. value).

6.  Security Considerations

   On a link where router advertisements Router Advertisements are few and far between, the
   detrimental effects of a rogue router that sends an unsolicited RA
   are greatly increased.  These rogue RAs can be prevented by using
   approaches like RA-Guard [RFC6105] and SeND [RFC3971] SEcure Neighbor Discovery
   (SEND) [RFC3971].

7.  IANA Considerations

   This document does not require any has no IANA action.

9. actions.

8.  References


8.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [RFC4861]  Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
              "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
              DOI 10.17487/RFC4861, September 2007,


   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in
              RFC 2119 Key Words", BCP 14, RFC 8174,
              DOI 10.17487/RFC8174, May 2017,

8.2.  Informative References

   [RFC3971]  Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander,
              "SEcure Neighbor Discovery (SEND)", RFC 3971,
              DOI 10.17487/RFC3971, March 2005,

   [RFC6105]  Levy-Abegnoli, E., Van de Velde, G., Popoviciu, C., and J.
              Mohacsi, "IPv6 Router Advertisement Guard", RFC 6105,
              DOI 10.17487/RFC6105, February 2011,

   [RFC6459]  Korhonen, J., Ed., Soininen, J., Patil, B., Savolainen,
              T., Bajko, G., and K. Iisakkila, "IPv6 in 3rd Generation
              Partnership Project (3GPP) Evolved Packet System (EPS)",
              RFC 6459, DOI 10.17487/RFC6459, January 2012,

   [RFC7066]  Korhonen, J., Ed., Arkko, J., Ed., Savolainen, T., and S.
              Krishnan, "IPv6 for Third Generation Partnership Project
              (3GPP) Cellular Hosts", RFC 7066, DOI 10.17487/RFC7066,
              November 2013, <https://www.rfc-editor.org/info/rfc7066>.



   The authors would like to thank the members of the 6man 6MAN efficient ND
   design team for their comments that led to the creation of this
   document.  The authors would also like to thank Lorenzo Colitti, Erik
   Kline, Jeena Rachel John, Brian Carpenter, Tim Chown, Fernando Gont,
   Warren Kumari Kumari, and Adam Roach for their comments and suggestions that
   improved this document.

Authors' Addresses

   Suresh Krishnan
   335 Rue Peel
   Montreal, QC

   Email: suresh@kaloom.com

   Jouni Korhonen
   Porkkalankatu 24
   FIN-00180 Helsinki
   Nordic Semiconductor ASA
   Metsanneidonkuja 10
   02130 Espoo

   Email: jouni.nospam@gmail.com

   Samita Chakrabarti
   United States of America

   Email: samita.chakrabarti@ericsson.com samita.chakrabarti@verizon.com

   Erik Nordmark
   Arista Networks
   Santa Clara, CA
   United States of America

   Email: nordmark@acm.org

   Andrew Yourtchenko
   6b de Kleetlaan
   Diegem  1831

   Email: ayourtch@cisco.com