IPv6 maintenance Working Group (6man) F. Gont
Internet-Draft SI6 Networks / UTN-FRH
Updates: 6106 (if approved) P. Simerda
Intended status: Standards Track
Expires: August 30, 2015 W. Liu
Huawei Technologies
February 26, 2015
Current issues with DNS Configuration Options for SLAAC
draft-gont-6man-slaac-dns-config-issues-01
Abstract
RFC 6106 specifies two Neighbor Discovery options that can be
included in Router Advertisement messages to convey information about
DNS recursive servers and DNS Search Lists. Small lifetime values
for the aforementioned options have been found to cause
interoperability problems in those network scenarios in which these
options are used to convey DNS-related information. This document
analyzes the aforementioned problem, and formally updates RFC 6106
such that these issues are mitigated.
Status of This Memo
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This Internet-Draft will expire on August 30, 2015.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Changing the Semantics of the 'Lifetime' field of RDNSS and
DNSSL options . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Changing the Default Values of the 'Lifetime' field of RDNSS
and DNSSL options . . . . . . . . . . . . . . . . . . . . . . 4
4. Use of Router Solicitations for active Probing . . . . . . . 4
5. Sanitize the received RDNSS/DNSSL 'Lifetime' Values . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . 5
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
8. Normative References . . . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
RFC 6106 [RFC6106] specifies two Neighbor Discovery (ND) [RFC4861]
options that can be included in Router Advertisement messages to
convey information about DNS recursive servers and DNS Search Lists.
Namely, the Recursive DNS Server (RDNSS) Option specifies the IPv6
addresses of recursive DNS servers, while the DNS Search List (DNSSL)
Option specifies a "search list" to be used when trying to resolve a
name by means of the DNS.
Each of this options include a "Lifetime" field which specifies the
maximum time, in seconds, during which the information included in
the option can be used by the receiving system. The aforementioned
"Lifetime" value is set as a function of the Neighbor Discovery
parameter 'MaxRtrAdvInterval', which specifies the maximum time
allowed between sending unsolicited multicast Router Advertisements
from an interface. The recommended bounds (MaxRtrAdvInterval <=
Lifetime <= 2*MaxRtrAdvInterval) have been found to be too short for
scenarios in which some Router Advertisement messages may be lost.
In such scenarios, hosts may fail to receive unsolicited Router
Advertisements and therefore fail to refresh the expiration time of
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