Neighbor Cache Entries on First-Hop Routers: Operational Considerations
draft-ietf-v6ops-nd-cache-init-05
v6ops J. Linkova
Internet-Draft Google
Intended status: Informational September 6, 2020
Expires: March 10, 2021
Neighbor Cache Entries on First-Hop Routers: Operational Considerations
draft-ietf-v6ops-nd-cache-init-05
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 discusses how the
neighbor discovery state machine on a first-hop router is causing
user-visible connectivity issues when a new (not being seen on the
network before) IPv6 address is being used. The various approaches
to mitigate the problem are described, with the proposed solution
fully documented in I-D.ietf-6man-grand.
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 https://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 March 10, 2021.
Copyright Notice
Copyright (c) 2020 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
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
Linkova Expires March 10, 2021 [Page 1]
Internet-Draft NC Entries Creation September 2020
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 . . . . . . . . . . . . . . . . . . 4
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. Proposed Solution . . . . . . . . . . . . . . . . . . . . . . 5
2.1. Solution Requirements . . . . . . . . . . . . . . . . . . 5
2.2. Solution Overview . . . . . . . . . . . . . . . . . . . . 5
3. Solutions Considered but Discarded . . . . . . . . . . . . . 6
3.1. Do Nothing . . . . . . . . . . . . . . . . . . . . . . . 7
3.2. Change to the Registration-Based Neighbor Discovery . . . 7
3.3. Host Sending NS to the Router Address from Its GUA . . . 7
3.4. Host Sending Router Solicitation from its GUA . . . . . . 8
3.5. Routers Populating Their Caches by Gleaning From Neighbor
Discovery Packets . . . . . . . . . . . . . . . . . . . . 9
3.6. Initiating Hosts-to-Routers Communication . . . . . . . . 9
3.7. Transit Dataplane Traffic From a New Address Triggering
Address Resolution . . . . . . . . . . . . . . . . . . . 10
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
5. Security Considerations . . . . . . . . . . . . . . . . . . . 10
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
7.1. Normative References . . . . . . . . . . . . . . . . . . 11
7.2. Informative References . . . . . . . . . . . . . . . . . 12
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction
The section 7.2.5 of [RFC4861] states: "When a valid Neighbor
Advertisement is received (either solicited or unsolicited), the
Neighbor Cache is searched for the target's entry. If no entry
exists, the advertisement SHOULD be silently discarded. There is no
need to create an entry if none exists, since the recipient has
apparently not initiated any communication with the target."
This approach is perfectly suitable for host-to-host communications,
which are in most cases bi-directional, and it could be expected that
if a host A has an neighbor cache entry for the host B IPv6 address,
host B also has the corresponding entry for the host A address in its
cache. However when a host communicates to off-link destinations via
its first-hop router, that logic does not apply. The most typical
Show full document text