draft-ietf-dnsop-resolver-priming-09.txt   draft-ietf-dnsop-resolver-priming-10.txt 
Network Working Group P. Koch Network Working Group P. Koch
Internet-Draft DENIC eG Internet-Draft DENIC eG
Intended status: Best Current Practice M. Larson Intended status: Best Current Practice M. Larson
Expires: March 19, 2017 P. Hoffman Expires: June 26, 2017 P. Hoffman
ICANN ICANN
September 15, 2016 December 23, 2016
Initializing a DNS Resolver with Priming Queries Initializing a DNS Resolver with Priming Queries
draft-ietf-dnsop-resolver-priming-09 draft-ietf-dnsop-resolver-priming-10
Abstract Abstract
This document describes the queries that a DNS resolver should emit This document describes the queries that a DNS resolver should emit
to initialize its cache. The result is that the resolver gets both a to initialize its cache. The result is that the resolver gets both a
current NS RRSet for the root zone and the necessary address current NS RRSet for the root zone and the necessary address
information for reaching the root servers. information for reaching the root servers.
Status of This Memo Status of This Memo
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on March 19, 2017. This Internet-Draft will expire on June 26, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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that configuration as a list of servers that will give authoritative that configuration as a list of servers that will give authoritative
answers to queries about the root. This has become a common answers to queries about the root. This has become a common
implementation choice for recursive resolvers, and is the topic of implementation choice for recursive resolvers, and is the topic of
this document. this document.
This document describes the steps needed for this common This document describes the steps needed for this common
implementation choice. Note that this is not the only way to start a implementation choice. Note that this is not the only way to start a
recursive name server with an empty cache, but it is the only one recursive name server with an empty cache, but it is the only one
described in [RFC1034]. Some implementers have chosen other described in [RFC1034]. Some implementers have chosen other
directions, some of which work well and others of which fail directions, some of which work well and others of which fail
(sometimes disastrously) under different conditions. (sometimes disastrously) under different conditions. For example, an
implementation that only gets the addresses of the root name servers
from configuration, not from the DNS as described in this document,
will have stale data that could cause slower resolution.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
This document only deals with recursive name servers (recursive This document only deals with recursive name servers (recursive
resolvers, resolvers) for the IN class. resolvers, resolvers) for the IN class.
2. Description of Priming 2. Description of Priming
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The priming response is expected to have an RCODE of NOERROR, and to The priming response is expected to have an RCODE of NOERROR, and to
have the AA bit set. Also, it is expected to have an NS RRSet in the have the AA bit set. Also, it is expected to have an NS RRSet in the
Answer section (because the NS RRSet originates from the root zone), Answer section (because the NS RRSet originates from the root zone),
and an empty Authority section (because the NS RRSet already appears and an empty Authority section (because the NS RRSet already appears
in the Answer section). There will also be an Additional section in the Answer section). There will also be an Additional section
with A and/or AAAA RRSets for the root name servers pointed at by the with A and/or AAAA RRSets for the root name servers pointed at by the
NS RRSet. NS RRSet.
Resolver software SHOULD treat the response to the priming query as a Resolver software SHOULD treat the response to the priming query as a
normal DNS response, just as it would use any other data fed to its normal DNS response, just as it would use any other data fed to its
cache. Resolver software SHOULD NOT expect exactly 13 NS RRs. cache. Resolver software SHOULD NOT expect exactly 13 NS RRs because
historically some root servers have returned fewer.
4.2. Completeness of the Response 4.2. Completeness of the Response
There are currently 13 root servers. All have one IPv4 address, and There are currently 13 root servers. All have one IPv4 address, and
12 of the 13 have an IPv6 address. The combined size of all the A 12 of the 13 have an IPv6 address. The combined size of all the A
and AAAA RRSets is 544 bytes. Not even counting the NS RRSet, this and AAAA RRSets is 544 bytes. Not even counting the NS RRSet, this
value exceeds the original 512 octet payload limit from [RFC1035]. value exceeds the original 512 octet payload limit from [RFC1035].
In the event of a response where the Additional section omits certain In the event of a response where the Additional section omits certain
root server address information, re-issuing of the priming query does root server address information, re-issuing of the priming query does
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