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Versions: 00 01 02 draft-ietf-dnsop-root-loopback

Network Working Group                                          W. Kumari
Internet-Draft                                                    Google
Intended status: Informational                                P. Hoffman
Expires: May 30, 2015                                     VPN Consortium
                                                       November 26, 2014


   Decreasing Access Time to Root Servers by Running One on Loopback
                  draft-wkumari-dnsop-root-loopback-02

Abstract

   Some DNS recursive resolvers have longer-than-desired round trip
   times to the closest DNS root server.  Such resolvers can greatly
   decrease the round trip time by running a copy of the full root zone
   on a loopback address (such as 127.0.0.1).  Typically, the vast
   majority of queries going to the root are for names that do not exist
   in the root zone, and the negative answers are cached for a much
   shorter period of time.  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

   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 http://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 May 30, 2015.

Copyright Notice

   Copyright (c) 2014 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
   (http://trustee.ietf.org/license-info) in effect on the date of



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   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
   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 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
   Appendix B.  Example Configurations of Common Implementations . .   6
     B.1.  Example Configuration: BIND 9.9 . . . . . . . . . . . . .   6
     B.2.  Example Configuration: Unbound 1.4 and NSD 4  . . . . . .   7
     B.3.  Example Configuration: Microsoft Windows Server 2012  . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

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 recursive 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
   an up-to-date root zone server on a loopback address on the same host
   as the recursive server, and that server is used when the recursive
   resolver uses for looking up root information.  The recursive
   resolver validates all responses from the root server on the loopback
   address, just as it would all responses from a remote root server.

   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



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   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.

   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 recursive
   resolver.

   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 be able to talk to an authoritative server (such
   as NSD) running on the same host.

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 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).

   A corollary of the above list is that authoritative data in the root
   zone used on the local authoritative server MUST be identical to the
   same data in the root zone for the DNS.  It is possible to change the
   unsigned data (the glue records) in the copy of the root zone, but
   such changes are likely to cause problems for the recursive server
   that accesses the local root zone.







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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.  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 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 specifies the local address as the
   place to look when it is looking for information from the root.  All
   responses from the root server must be validated using DNSSEC.

   Note that using this configuration will cause the recursive resolver
   to fail if the local root zone server fails.  See Appendix B for more
   discussion of this for specific software.

   To test the proper operation of the recursive resolver with the local
   root server, use a DNS client to send a query for the SOA of the root
   to the recursive server.  Make sure the response that comes back does
   not have the AD bit in the message header set.

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 giving bad responses in the same way
   as any recursive resolver that does not do DNSSEC validation on
   responses from a remote root server.



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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.  For example, Bill Manning described something similar
   in his doctoral dissertation in 2013.

   Evan Hunt contributed greatly to the logic in the requirements.
   Other significant contributors include Wouter Wijngaards, Tony Hain
   Doug Barton, and Greg Lindsay.

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 sources of the root zone supported by ICANN:

   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

   Currently, the root can be retrieved by zone transfer (AXFR) from the
   following root server operators:

   o  b.root-servers.net

   o  c.root-servers.net

   o  f.root-servers.net

   o  g.root-servers.net

   o  k.root-servers.net






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Appendix B.  Example Configurations of Common Implementations

   This section shows fragments of configurations for some popular
   recursive server software that is believed to correctly implement the
   requirements given in this document.

   The IPv4 and IPv6 addresses in this section were checked recently by
   testing for AXFR over TCP from each address for the known single-
   letter names in the root-servers.net zone.

   The examples here use a loopback address of 127.12.12.12, but typical
   installations will use 127.0.0.1.  The different address is used in
   order to emphasize that the root server does not need to be on the
   device at "localhost".

B.1.  Example Configuration: BIND 9.9

   BIND acts both as a recursive resolver and an authoritative server.
   Because of this, there is "fate sharing" between the two servers in
   the following configuration.  That is, if the root server dies, it is
   likely that all of BIND is dead.

   Using this configuration, queries for information in the root zone
   are returned with the AA bit not set.

   When slaving a zone, BIND will treat zone data differently if it is
   slaved into a separate view (or a separate instance of the software)
   versus slaving the zone into the same view or instance that is also
   performing the recursion.

   Validation:  When using separate views or separate instances, the DS
      records in the slaved zone will be validated as the zone data is
      accessed by the recursive server.  When using the same view, this
      validation does not occur for the slaved zone.

   Caching:  When using separate views or instances, the recursive
      server will cache all of the queries for the slaved zone, just as
      it would using the traditional root hints method.  Thus, as the
      zone in the other view or instance is refreshed or updated,
      changed information will not appear in the recursive server until
      the TTL of the old record times out.  Currently the TTL for DS and
      delegation NS records is two days.  When using the same view, all
      zone data in the recursive server will be updated as soon as it
      receives its copy of the zone.







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   view root {
       match-destinations { 127.12.12.12; };
       zone "." {
           type slave;
           file "rootzone.db";
           notify no;
           masters {
               192.228.79.201; # b.root-servers.net
               192.33.4.12;    # c.root-servers.net
               192.5.5.241;    # f.root-servers.net
               192.112.36.4;   # g.root-servers.net
               193.0.14.129;   # k.root-servers.net
               2001:500:84::b; # b.root-servers.net
               2001:500:2f::f; # f.root-servers.net
               2001:7fd::1;    # k.root-servers.net
           };
       };
   };

   view recursive {
       dnssec-validation auto;
       allow-recursion { any; };
       recursion yes;
       zone "." {
           type static-stub;
           server-addresses { 127.12.12.12; };
       };
   };

B.2.  Example Configuration: Unbound 1.4 and NSD 4

   Unbound and NSD are separate software packages.  Because of this,
   there is no "fate sharing" between the two servers in the following
   configurations.  That is, if the root server instance (NSD) dies, the
   recursive resolver instance (Unbound) will probably keep running, but
   will not be able to resolve any queries for the root zone.
   Therefore, the administrator of this configuration might want to
   carefully monitor the NSD instance and restart it immediately if it
   dies.

   Using this configuration, queries for information in the root zone
   are returned with the AA bit not set.









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   # Configuration for Unbound
   server:
       do-not-query-localhost: no
   stub-zone:
       name: "."
       stub-prime: no
       stub-addr: 127.12.12.12

   # Configuration for NSD
   server:
       ip-address: 127.12.12.12
   zone:
       name: "."
       request-xfr: 192.228.79.201 NOKEY # b.root-servers.net
       request-xfr: 192.33.4.12 NOKEY    # c.root-servers.net
       request-xfr: 192.5.5.241 NOKEY    # f.root-servers.net
       request-xfr: 192.112.36.4 NOKEY   # g.root-servers.net
       request-xfr: 193.0.14.129 NOKEY   # k.root-servers.net
       request-xfr: 2001:500:84::b NOKEY # b.root-servers.net
       request-xfr: 2001:500:2f::f NOKEY # f.root-servers.net
       request-xfr: 2001:7fd::1 NOKEY    # k.root-servers.net

B.3.  Example Configuration: Microsoft Windows Server 2012

   Windows Server 2012 contains a DNS server in the "DNS Manager"
   component.  When activated, that component acts as a recursive
   server.  DNS Manager can also act as an authoritative server.

   Using this configuration, queries for information in the root zone
   are returned with the AA bit set.

   The steps to configure DNS Manager to implement the requirements in
   this document are:

   1.  Launch the DNS Manager GUI.  This can be done from the command
       line ("dnsmgmt.msc") or from the Service Manager (the "DNS"
       command in the "Tools" menu).

   2.  In the hierarchy under the server on which the service is
       running, right-click on the "Forward Lookup Zones", and select
       "New Zone".  This brings up a succession of dialog boxes.

   3.  In the "Zone Type" dialog box, select "Secondary zone".

   4.  In the "Zone Name" dialog box, enter ".".

   5.  In the "Master DNS Servers" dialog box, enter "b.root-
       servers.net".  The system validates that it can do a zone



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       transfer from that server.  (After this configuration is
       completed, DNS Manager will attempt to transfer from all of the
       root zone servers.)

   6.  In the "Completing the New Zone Wizard" dialog box, click
       "Finish".

   7.  Verify that the DNS Manager is acting as a recursive resolver.
       Right-click on the server name in the hierarch, choosing the
       "Advanced" tab in the dialog box.  See that "Disable recursion
       (also disables forwarders)" is not selected, and that "Enable
       DNSSEC validation for remote responses" is selected.

Authors' Addresses

   Warren Kumari
   Google

   Email: Warren@kumari.net


   Paul Hoffman
   VPN Consortium

   Email: paul.hoffman@vpnc.org


























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