Network Working Group W. Kumari, Ed.
Internet-Draft Google
Intended status: Informational P. Hoffman, Ed.
Expires: April 28, 2015 VPN Consortium
October 25, 2014
Decreasing Access Time to Root Servers by Running One on Loopback
draft-wkumari-dnsop-root-loopback-00
Abstract
Some DNS recursive resolvers have longer-than-desired round trip
times to the closest DNS root server. Such resolvers can greatly
decrease the rount trip time by running a copy of the full root zone
on a loopback address (such as 127.0.0.1). This document shows how
to start and maintain such a copy of the root zone in a manner that
is secure for the operator of the recursive resolver and does not
pose a threat to other users of the DNS.
Status of This Memo
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This Internet-Draft will expire on April 28, 2015.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Notation . . . . . . . . . . . . . . . . . . 3
2. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Operation of the Root Zone on the Loopback Address . . . . . 4
4. Using the Root Zone Server on the Loopback Address . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 4
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
8. Normative References . . . . . . . . . . . . . . . . . . . . 5
Appendix A. Current Sources of the Root Zone . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
DNS recursive resolvers have to answer all queries from their
customers, even those which are for domain names that do not exist.
For each queried name that has a top level domain (TLD) that is not
in the recurive resolver's cache, the resolver must send a query to a
root server to get the information for that TLD, or to find out that
the TLD does not exist. If there is a slow path between the
recursive resolver and the closest root server, getting slow
responses to these queries has a negative effect on the resolver's
customers.
This document describes a method for the operator of a recursive
resolver to greatly speed these queries. The basic idea is to create
a validated, up-to-date root zone server on a loopback address on the
same host as the recursive server, and that server is added to the
list of root zones that the recursive resolver uses for looking up
root information. If the new server is working correctly, it will
quickly become the preferred root server for the recursive resolver;
if the new server fails to work (such as because it cannot get
updates to the zone), the recursive resolver will use other root
servers, as it does now.
The primary goal of this design is to provide faster negative
responses to stub resolver queries that contain junk queries. This
design will probably have little effect on getting faster positive
responses to stub resolver for good queries on TLDs, because the data
for those zones is usually long-lived and already in the cache of the
recursive resolver; thus, getting faster positive responses is a non-
goal of this design.
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This design explicitly only allows the new root zone server to be run
on a loopback address. This prevents the server from serving
authoritative answers to any system other than the recurisve
resolver.
This design can possibly be implemented by hand, but it is much more
likely that the creators of recursive resolver software will
implement it and the operator simply needs to turn on the feature.
Note that this design requires the addition of authoritative name
server software running on the same machine as the recursive
resolver. Thus, recursive resolver software such as BIND will not
need to add much new functionality, but recursive resolver software
such as Unbound will need to add software that acts as an
authoritative server.
1.1. Requirements Notation
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
2. Requirements
In the discussion below, the term "legacy operation" means the way
that a recursive resolver acts when it is not using the mechanism
describe in this document, namely as a normal validating recursive
resolver with no other special features.
In order to implement the mechanism described in this document:
o The system MUST be able to validate a zone with DNSSEC.
o The system MUST have an up-to-date copy of the DNS root key.
o The system MUST be able to retrieve a copy of the entire root zone
(including all DNSSEC-related records).
o The system MUST be able to run an authoritative server on one of
the IPv4 loopback addresses (that is, an address in the range
127/8).
o The authoritative server in the system MUST send error responses
(RCODE 2, also known as "SERVFAIL") if the validated data in the
root zone it is serving is out of date.
o The recursive resolver MUST be able to add an additional address
to its list of addresses of authoritative root servers, and MUST
treat that additional address the same as the other addresses.
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3. Operation of the Root Zone on the Loopback Address
The operation of an authoritative server for the root in the system
described here can be done separately from the operation of the
recursive resolver.
The steps to set up the root zone are:
1. Retrieve a copy of the root zone. (See Appendix A for some
current locations of sources.)
2. Validate the zone using normal DNSSEC validation.
3. Start the authoritative server with the root zone on a loopback
address that is not in use. This would typically be 127.0.0.1,
but if that address is in use, any address in 127/8 is
acceptable.
The contents of the root zone must be refreshed using the timers from
the SOA record in root zone, as described in [RFC1035]. If the
contents of the zone cannot be refreshed with validated information
before the expire time, the server MUST return a SERVFAIL error
response for all queries until the zone can be successfully be set up
again.
4. Using the Root Zone Server on the Loopback Address
A recursive resolver that wants to use a root zone server operating
as described in Section 3 simply adds the address of the server to
its list of authoritative servers for the root zone. The resolver's
round-robin search mechanism will begin to strongly prefer this new
server, just as it would any root zone server that has an extremely
short round trip time.
5. IANA Considerations
This document requires no action from the IANA.
6. Security Considerations
A system that does not follow the DNSSEC-related requirements given
in Section 2 can be fooled into givning bad responses in the same way
as any recursive resolver that does not do DNSSEC validation on
responses from the root zone.
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7. Acknowledgements
The editors fully acknowledge that this is not a new concept, and
that we have chatted with many people about this. In fact, this
concept may already have been implemented without the knowledge of
the authors.
8. Normative References
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
Appendix A. Current Sources of the Root Zone
The root zone can be retrieved from anywhere as long as it comes with
all the DNSSEC records needed for validation. Currently, there are
three well-known sources of the root zone:
o From ICANN via FTP at ftp://rs.internic.net/domain/root.zone
o From ICANN via HTTP at http://www.internic.net/domain/root.zone
o From ICANN by AXFR from DNS servers at xfr.lax.dns.icann.org and
xfr.cjr.dns.icann.org
Authors' Addresses
Warren Kumari (editor)
Google
Email: Warren@kumari.net
Paul Hoffman (editor)
VPN Consortium
Email: paul.hoffman@vpnc.org
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