Gratuitous Neighor Discovery: Creating Neighbor Cache Entries on First-Hop Routers
draft-linkova-6man-grand-00

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Last updated 2019-10-28
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IPv6 Maintenance                                              J. Linkova
Internet-Draft                                                    Google
Updates: 4861 (if approved)                             October 27, 2019
Intended status: Standards Track
Expires: April 29, 2020

Gratuitous Neighor Discovery: Creating Neighbor Cache Entries on First-
                              Hop Routers
                      draft-linkova-6man-grand-00

Abstract

   Neighbor Discovery (RFC4861) is used by IPv6 nodes to determine the
   link-layer addresses of neighboring nodes as well as to discover and
   maintain reachability information.  This document updates [RFC4861]
   to allow routers to proactively create a Neighbor Cache entry when a
   new IPv6 address is assigned to a host.  It also updates [RFC4862]
   and [RFC4429] recommending hosts to send unsolicited Neighbor
   Advertisements upon assigning a new IPv6 address.  The proposed
   change will minimize the delay and packet loss when a host initiate
   connections to off-link destination from a new IPv6 address.

Status of This Memo

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   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on April 29, 2020.

Copyright Notice

   Copyright (c) 2019 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
   (https://trustee.ietf.org/license-info) in effect on the date of

Linkova                  Expires April 29, 2020                 [Page 1]
Internet-Draft                Gratuitous ND                 October 2019

   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
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   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.  Requirements Language . . . . . . . . . . . . . . . . . .   3
     1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Proposed Changes to Neighbor Discovery  . . . . . . . . . . .   3
     2.1.  Hosts Sending Gratuitous Neighbor Advertisements  . . . .   4
     2.2.  Routers Creating Cache Entries Upon Receiving Unsolicited
           Neighbor Advertisements . . . . . . . . . . . . . . . . .   4
   3.  Avoiding Disruption . . . . . . . . . . . . . . . . . . . . .   5
   4.  Modifications to RFC-Mandated Behavior  . . . . . . . . . . .   6
     4.1.  Modification to RFC4861 Neighbor Discovery for IP version
           6 (IPv6)  . . . . . . . . . . . . . . . . . . . . . . . .   6
       4.1.1.  Modification to the section 7.2.5 . . . . . . . . . .   6
       4.1.2.  Modification to the section 7.2.6 . . . . . . . . . .   7
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   8
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   9
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   The Neighbor Discovery state machine defined in [RFC4861] implies
   that communications between IPv6 nodes are in most cases bi-
   directional and if a host A is trying to communicate to its neighbor,
   host B, the return traffic flows could be expected.  So when the host
   A start the address resolution process, the target host would also
   create an entry for the host A address in its neighbor cache.  That
   entry will be used for sending the return traffic to the host A.

   However when a host sends traffic to off-link destinations the
   different scenario might be observed.  After receiving an RA the host
   populates its neighbor cache with the default router address and is
   able to send traffic to off-link destinations.  At the same time the
   router does not have any cache entries for the host global addresses
   and therefore needs to start address resolution upon receiving the
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