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RFC 7534

Informational
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AS112 Nameserver Operations

Obsoletes:    6304


Top       ToC       Page 1 
Internet Engineering Task Force (IETF)                          J. Abley
Request for Comments: 7534                                     Dyn, Inc.
Obsoletes: 6304                                             W. Sotomayor
Category: Informational                                            OttIX
ISSN: 2070-1721                                                 May 2015


                      AS112 Nameserver Operations

Abstract

   Many sites connected to the Internet make use of IPv4 addresses that
   are not globally unique.  Examples are the addresses designated in
   RFC 1918 for private use within individual sites.

   Devices in such environments may occasionally originate Domain Name
   System (DNS) queries (so-called "reverse lookups") corresponding to
   those private-use addresses.  Since the addresses concerned have only
   local significance, it is good practice for site administrators to
   ensure that such queries are answered locally.  However, it is not
   uncommon for such queries to follow the normal delegation path in the
   public DNS instead of being answered within the site.

   It is not possible for public DNS servers to give useful answers to
   such queries.  In addition, due to the wide deployment of private-use
   addresses and the continuing growth of the Internet, the volume of
   such queries is large and growing.  The AS112 project aims to provide
   a distributed sink for such queries in order to reduce the load on
   the corresponding authoritative servers.  The AS112 project is named
   after the Autonomous System Number (ASN) that was assigned to it.

   This document describes the steps required to install a new AS112
   node and offers advice relating to such a node's operation.

   This document obsoletes RFC 6304.

Page 2 
Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7534.

Copyright Notice

   Copyright (c) 2015 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
   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.

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Table of Contents

   1. Introduction ....................................................4
   2. AS112 DNS Service ...............................................4
      2.1. Approach ...................................................4
           2.1.1. Direct Delegation ...................................4
           2.1.2. DNAME Redirection ...................................5
      2.2. Zones ......................................................5
      2.3. Nameservers ................................................6
   3. Installation of a New Node ......................................6
      3.1. Useful Background Knowledge ................................6
      3.2. Topological Location .......................................6
      3.3. Operating System and Host Considerations ...................7
      3.4. Routing Software ...........................................7
      3.5. DNS Software ..............................................10
      3.6. Testing a Newly Installed Node ............................15
   4. Operations .....................................................16
      4.1. Monitoring ................................................16
      4.2. Downtime ..................................................16
      4.3. Statistics and Measurement ................................16
   5. Communications .................................................17
   6. On the Future of AS112 Nodes ...................................17
   7. IANA Considerations ............................................18
      7.1. General ...................................................18
      7.2. IANA Actions ..............................................18
           7.2.1. IPv6 Transport for Direct Delegation AS112
                  Servers ............................................18
           7.2.2. Registration in the Special-Purpose AS
                  Numbers Registry ...................................19
           7.2.3. Registration in the IANA IPv4
                  Special-Purpose Address Registry ...................19
           7.2.4. Registration in the IANA IPv6
                  Special-Purpose Address Registry ...................19
   8. Security Considerations ........................................20
   9. References .....................................................21
      9.1. Normative References ......................................21
      9.2. Informative References ....................................22
   Appendix A. A Brief History of AS112 ..............................23
   Appendix B. Changes since RFC 6304 ................................23
   Acknowledgements ..................................................24
   Authors' Addresses ................................................24

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1.  Introduction

   Many sites connected to the Internet make use of IPv4 addresses that
   are not globally unique.  Examples are the addresses designated in
   [RFC1918] for private use within individual sites.

   Devices in such environments may occasionally originate Domain Name
   System (DNS) [RFC1034] queries (so-called "reverse lookups")
   corresponding to those private-use addresses.  Since the addresses
   concerned have only local significance, it is good practice for site
   administrators to ensure that such queries are answered locally
   [RFC6303].  However, it is not uncommon for such queries to follow
   the normal delegation path in the public DNS instead of being
   answered within the site.

   It is not possible for public DNS servers to give useful answers to
   such queries.  In addition, due to the wide deployment of private-use
   addresses and the continuing growth of the Internet, the volume of
   such queries is large and growing.  The AS112 project aims to provide
   a distributed sink for such queries in order to reduce the load on
   the IN-ADDR.ARPA authoritative servers [RFC5855].

   The AS112 project encompasses a loosely coordinated collection of
   independently operated nameservers.  Each nameserver functions as a
   single node in an AS112 anycast cloud [RFC4786] and is configured to
   answer authoritatively for a particular set of nominated zones.

   The AS112 project is named after the Autonomous System Number (ASN)
   that was assigned to it (see Appendix A).

2.  AS112 DNS Service

2.1.  Approach

2.1.1.  Direct Delegation

   The AS112 project currently uses an approach whereby zones whose
   traffic should be directed towards an AS112 sink should be directly
   delegated to AS112 nameservers.  Correspondingly, each AS112 node is
   manually configured to answer appropriately for those zones.

   The guidance in this document describes this capability for the zones
   that were originally delegated in this fashion.  AS112 nodes that
   were implemented in accordance with the guidance found here will
   continue to provide service for those zones.

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2.1.2.  DNAME Redirection

   [RFC7535] describes a different approach whereby queries towards
   specific zones are redirected to an empty zone also hosted on AS112
   servers, using DNAME [RFC6672].

   The guidance in this document introduces this capability, allowing
   any zone administrator to sink query traffic in AS112 infrastructure
   without requiring changes to any AS112 node.

2.2.  Zones

   To support Direct Delegation AS112 service, AS112 nameservers answer
   authoritatively for the following zones, corresponding to [RFC1918]
   private-use netblocks:

   o  10.IN-ADDR.ARPA

   o  16.172.IN-ADDR.ARPA, 17.172.IN-ADDR.ARPA, ..., 31.172.IN-ADDR.ARPA

   o  168.192.IN-ADDR.ARPA

   and the following zone, corresponding to the "link local" netblock
   169.254.0.0/16 listed in [RFC6890]:

   o  254.169.IN-ADDR.ARPA

   To support DNAME redirection AS112 service, AS112 nameservers answer
   authoritatively for the following zone, as specified in [RFC7535]:

   o  EMPTY.AS112.ARPA

   To aid identification of AS112 anycast nodes, each node also answers
   authoritatively for the following zones:

   o  HOSTNAME.AS112.NET

   o  HOSTNAME.AS112.ARPA

   See Section 3.5 for the recommended contents of all these zones.

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2.3.  Nameservers

   To support Direct Delegation AS112 service, the relevant zones listed
   in Section 2.2 are delegated to the two nameservers
   BLACKHOLE-1.IANA.ORG (192.175.48.6, 2620:4f:8000::6) and
   BLACKHOLE-2.IANA.ORG (192.175.48.42, 2620:4f:8000::42).

   Additionally, the server PRISONER.IANA.ORG (192.175.48.1,
   2620:4f:8000::1) is listed in the MNAME field of the SOA records of
   the IN-ADDR.ARPA zones served by AS112 nameservers.
   PRISONER.IANA.ORG receives mainly dynamic update queries.

   The addresses of all these nameservers are covered by the single IPv4
   prefix 192.175.48.0/24 and the IPv6 prefix 2620:4f:8000::/48.  To
   date, IPv6 transport for these nameservers has only been available
   for pre-production testing.  IANA has added AAAA RRSets for the owner
   names of these nameservers; see Section 7.

   To support DNAME redirection AS112 service, the single zone
   EMPTY.AS112.ARPA is delegated to the single nameserver
   BLACKHOLE.AS112.ARPA (192.31.196.1, 2001:4:112::1).  The addresses of
   that nameserver are covered by the single IPv4 prefix 192.31.196.0/24
   and the single IPv6 prefix 2001:4:112::/48.

3.  Installation of a New Node

3.1.  Useful Background Knowledge

   Installation of an AS112 node is relatively straightforward.
   However, experience in the following general areas may prove useful:

   o  inter-domain routing with BGP [RFC4271];

   o  DNS authoritative server operations; and

   o  anycast [RFC4786] distribution of DNS services.

3.2.  Topological Location

   AS112 nodes may be located anywhere on the Internet.  For nodes that
   are intended to provide a public service to the Internet community
   (as opposed to private use), it may well be advantageous to choose a
   location that is easily (and cheaply) reachable by multiple
   providers, such as an Internet Exchange Point.

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   AS112 nodes may advertise their service prefix to BGP peers for local
   use (analogous to a conventional peering relationship between two
   providers) or for global use (analogous to a customer relationship
   with one or more providers).

   It is good operational practice to notify the community of users that
   may fall within the reach of a new AS112 node before it is installed.
   At an Internet Exchange, local mailing lists usually exist to
   facilitate such announcements.  For nodes that are intended to be
   globally reachable, coordination with other AS112 operators is highly
   recommended.  See also Section 5.

3.3.  Operating System and Host Considerations

   Examples in this document are based on UNIX and UNIX-like operating
   systems, but other operating systems exist that are suitable for use
   in construction of an AS112 node.

   The chosen platform should include either support for cloned loopback
   interfaces or the capability to bind multiple addresses to a single
   loopback interface.  The addresses of the nameservers listed in
   Section 2.3 will be configured on these interfaces in order that the
   DNS software can respond to queries properly.

   A host that is configured to act as an AS112 anycast node should be
   dedicated to that purpose and should not be used to simultaneously
   provide other services.  This guidance is provided due to the
   unpredictable (and occasionally high) traffic levels that AS112 nodes
   have been seen to attract.

   System startup scripts should be arranged such that the various
   AS112-related components start automatically following a system
   reboot.  The order in which interfaces are configured and software
   components started should be arranged such that routing software
   startup follows DNS software startup, and DNS software startup
   follows loopback interface configuration.

   Wrapper scripts or other arrangements should be employed to ensure
   that the anycast service prefix for AS112 is not advertised while
   either the anycast addresses are not configured or the DNS software
   is not running.

3.4.  Routing Software

   AS112 nodes signal the availability of AS112 nameservers to the
   Internet using BGP [RFC4271]: each AS112 node is a BGP speaker and
   announces the prefixes 192.175.48.0/24 and 2620:4f:8000::/48 to the
   Internet with origin AS 112 (see also Section 2.3).

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   The examples in this document are based on the Quagga Routing Suite
   <http://www.quagga.net> running on Linux, but other software packages
   exist that also provide suitable BGP support for AS112 nodes.

   The "bgpd.conf" file is used by Quagga's bgpd daemon, which provides
   BGP support.  The router ID in this example is 203.0.113.1; the AS112
   node peers with external peers 192.0.2.1, 192.0.2.2, 2001:db8::1, and
   2001:db8::2.  Note that the local AS number is 112, and the service
   prefixes originated from the AS112 node to support Direct Delegation
   service are 192.175.48.0/24 and 2620:4f:8000::/48; the IPv4 prefix
   192.31.196.0/24 and the IPv6 prefix 2001:4:112::/48 support DNAME
   redirection.

   For clarity, an IPv4-only AS112 node need not configure any of the
   IPv6 elements that follow; similarly, an IPv6-only AS112 node need
   not configure any of the IPv4 elements.  Such single-stack hosts can
   still contribute usefully to IPv4 and IPv6 AS112 services, however,
   and single-stack operation is not discouraged.

   ! bgpd.conf
   !
   hostname as112-bgpd
   password <something>
   enable password <supersomething>
   !
   ! Note that all AS112 nodes use the local Autonomous System Number
   ! 112, and originate the IPv4 prefixes 192.175.48.0/24 and
   ! 192.31.196.0/24 and the IPv6 prefixes 2620:4f:8000::/48 and
   ! 2001:4:112::/48.
   !
   ! All other addresses shown below are illustrative, and
   ! actual numbers will depend on local circumstances.
   !
   ! IPv4-only or IPv6-only AS112 nodes should omit advertisements
   ! for address families they do not support.
   !
   router bgp 112
    bgp router-id 203.0.113.1
    neighbor 192.0.2.1 remote-as 64496
    neighbor 192.0.2.1 next-hop-self
    neighbor 192.0.2.1 prefix-list AS112-v4 out
    neighbor 192.0.2.1 filter-list 1 out
   !
    neighbor 192.0.2.2 remote-as 64497
    neighbor 192.0.2.2 next-hop-self
    neighbor 192.0.2.2 prefix-list AS112-v4 out
    neighbor 192.0.2.2 filter-list 1 out
   !

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    neighbor 2001:db8::1 remote-as 64498
    neighbor 2001:db8::1 next-hop-self
    neighbor 2001:db8::1 prefix-list AS112-v6 out
    neighbor 2001:db8::1 filter-list 1 out
   !
    neighbor 2001:db8::2 remote-as 64499
    neighbor 2001:db8::2 next-hop-self
    neighbor 2001:db8::2 prefix-list AS112-v6 out
    neighbor 2001:db8::2 filter-list 1 out
   !
    network 192.175.48.0/24
    network 192.31.196.0/24
   !
    address-family ipv6 unicast
     network 2620:4f:8000::/48
     network 2001:4:112::/48
    exit-address-family
   !
   ip prefix-list AS112-v4 permit 192.175.48.0/24
   ip prefix-list AS112-v4 permit 192.31.196.0/24
   !
   ipv6 prefix-list AS112-v6 permit 2620:4f:8000::/48
   ipv6 prefix-list AS112-v6 permit 2001:4:112::/48
   !
   ip as-path access-list 1 permit ^$

   The configuration above includes two restrictions on what the AS112
   should advertise to its BGP neighbours: a prefix filter that permits
   only the service prefixes, and an AS_PATH filter that matches only
   locally originated routes.  Together, these measures prevent the node
   from becoming a transit point for its adjacent ASes.

   The "zebra.conf" file is required to provide integration between
   protocol daemons (bgpd, in this case) and the kernel.

   ! zebra.conf
   !
   hostname as112
   password <something>
   enable password <supersomething>
   !
   interface lo
   !
   interface eth0
   !

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3.5.  DNS Software

   Although the queries received by AS112 nodes are definitively
   misdirected, it is important that they be answered in a manner that
   is accurate and consistent.  For this reason, AS112 nodes operate as
   fully functional and standards-compliant DNS authoritative servers
   [RFC1034], and hence require appropriate DNS software.

   Examples in this document are based on ISC BIND9
   <http://www.isc.org/software/BIND/>, but other DNS software exists
   that is suitable for use in construction of an AS112 node.

   The following is a sample BIND9 "named.conf" file for a dedicated
   AS112 server.  Note that the nameserver is configured to act as an
   authoritative-only server (i.e., recursion is disabled).  The
   nameserver is also configured to listen on the various AS112 anycast
   nameserver addresses, as well as its local addresses.

   A basic logging example is included in the sample as well.  AS112
   operators may exercise discretion at the amount of logging detail
   they desire or the type of logging they may use in the maintenance of
   their node.  The detail of information can then be used to single out
   bad implementors or badly managed nameservers, or it can be used for
   simple measurement analysis.

   // named.conf

   // Global options

   options {
     listen-on {
       127.0.0.1;         // localhost

     // The following address is node-dependent and should be set to
     // something appropriate for the new AS112 node.

       203.0.113.1;       // local address (globally unique, unicast)

     // The following addresses are used to support Direct Delegation
     // AS112 service and are the same for all AS112 nodes.

       192.175.48.1;      // prisoner.iana.org (anycast)
       192.175.48.6;      // blackhole-1.iana.org (anycast)
       192.175.48.42;     // blackhole-2.iana.org (anycast)

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     // The following address is used to support DNAME redirection
     // AS112 service and is the same for all AS112 nodes.

       192.31.196.1;      // blackhole.as112.arpa (anycast)
     };

     listen-on-v6 {
       ::1;               // localhost

     // The following addresses are used to support Direct Delegation
     // AS112 service and are the same for all AS112 nodes.

       2620:4f:8000::1;   // prisoner.iana.org (anycast)
       2620:4f:8000::6;   // blackhole-1.iana.org (anycast)
       2620:4f:8000::42;  // blackhole-2.iana.org (anycast)

     // The following address is used to support DNAME redirection
     // AS112 service and is the same for all AS112 nodes.

       2001:4:112::1;    // blackhole.as112.arpa (anycast)
     };

     directory "/var/named";
     recursion no;        // authoritative-only server
   };

   // Log queries, so that when people call us about unexpected
   // answers to queries they didn't realise they had sent, we
   // have something to talk about.  Note that activating this
   // naively has the potential to create high CPU load and consume
   // enormous amounts of disk space.  This example retains 2 old
   // versions at a maximum of 500 MB each before rotating out the
   // oldest one.

   logging {
     channel "querylog" {
       file "/var/log/query.log" versions 2 size 500m;
       print-time yes;
     };
     category queries { querylog; };
   };

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   // Direct Delegation AS112 Service

   // RFC 1918

   zone "10.in-addr.arpa" { type master; file "db.dd-empty"; };
   zone "16.172.in-addr.arpa" { type master; file "db.dd-empty"; };
   zone "17.172.in-addr.arpa" { type master; file "db.dd-empty"; };
   zone "18.172.in-addr.arpa" { type master; file "db.dd-empty"; };
   zone "19.172.in-addr.arpa" { type master; file "db.dd-empty"; };
   zone "20.172.in-addr.arpa" { type master; file "db.dd-empty"; };
   zone "21.172.in-addr.arpa" { type master; file "db.dd-empty"; };
   zone "22.172.in-addr.arpa" { type master; file "db.dd-empty"; };
   zone "23.172.in-addr.arpa" { type master; file "db.dd-empty"; };
   zone "24.172.in-addr.arpa" { type master; file "db.dd-empty"; };
   zone "25.172.in-addr.arpa" { type master; file "db.dd-empty"; };
   zone "26.172.in-addr.arpa" { type master; file "db.dd-empty"; };
   zone "27.172.in-addr.arpa" { type master; file "db.dd-empty"; };
   zone "28.172.in-addr.arpa" { type master; file "db.dd-empty"; };
   zone "29.172.in-addr.arpa" { type master; file "db.dd-empty"; };
   zone "30.172.in-addr.arpa" { type master; file "db.dd-empty"; };
   zone "31.172.in-addr.arpa" { type master; file "db.dd-empty"; };
   zone "168.192.in-addr.arpa" { type master; file "db.dd-empty"; };

   // RFC 6890

   zone "254.169.in-addr.arpa" { type master; file "db.dd-empty"; };

   // DNAME redirection AS112 Service

   zone "empty.as112.arpa" { type master; file "db.dr-empty"; };

   // Also answer authoritatively for the HOSTNAME.AS112.NET and
   // HOSTNAME.AS112.ARPA zones, which contain data of operational
   // relevance.

   zone "hostname.as112.net" {
     type master;
     file "db.hostname.as112.net";
   };

   zone "hostname.as112.arpa" {
     type master;
     file "db.hostname.as112.arpa";
   };

Top      ToC       Page 13 
   The "db.dd-empty" file follows, below.  This is the source data used
   to populate all the IN-ADDR.ARPA zones listed in Section 2.2 that
   support Direct Delegation AS112 service.  Note that the RNAME
   specified in the SOA record corresponds to
   hostmaster@root-servers.org, a suitable email address for receiving
   technical queries about these zones.

   ; db.dd-empty
   ;
   ; Empty zone for Direct Delegation AS112 service.
   ;
   $TTL    1W
   @  IN  SOA  prisoner.iana.org. hostmaster.root-servers.org. (
                                  1       ; serial number
                                  1W      ; refresh
                                  1M      ; retry
                                  1W      ; expire
                                  1W )    ; negative caching TTL
   ;
          NS     blackhole-1.iana.org.
          NS     blackhole-2.iana.org.
   ;
   ; There should be no other resource records included in this zone.
   ;
   ; Records that relate to RFC 1918-numbered resources within the
   ; site hosting this AS112 node should not be hosted on this
   ; nameserver.

   The "db.dr-empty" file follows, below.  This is the source data used
   to populate the EMPTY.AS112.ARPA zone that supports DNAME redirection
   AS112 service.  Note that the RNAME specified in the SOA record
   corresponds to noc@dns.icann.org, a suitable email address for
   technical queries about this zone.

   ; db.dr-empty
   ;
   ; Empty zone for DNAME redirection AS112 service.
   ;
   $TTL    1W
   @  IN  SOA  blackhole.as112.arpa. noc.dns.icann.org. (
                                  1       ; serial number
                                  1W      ; refresh
                                  1M      ; retry
                                  1W      ; expire
                                  1W )    ; negative caching TTL
   ;
          NS     blackhole.as112.arpa.
   ;

Top      ToC       Page 14 
   ; There should be no other resource records included in this zone.
   ;
   ; Records that relate to RFC 1918-numbered resources within the
   ; site hosting this AS112 node should not be hosted on this
   ; nameserver.

   The "db.hostname.as112.net" and "db.hostname.as112.arpa" files
   follow, below.  These zones contain various resource records that
   provide operational data to users for troubleshooting or measurement
   purposes; the data should be edited to suit local circumstances.
   Note that the responses to the queries "HOSTNAME.AS112.NET IN TXT"
   and "HOSTNAME.AS112.ARPA IN TXT" should fit within a 512-octet DNS/
   UDP datagram: i.e., it should be available over UDP transport without
   requiring EDNS0 support by the client.

   The optional LOC record [RFC1876] included in each zone apex provides
   information about the geospatial location of the node.

   Where software implementations support it, operational data should
   also be carried using NSID [RFC5001].

   ; db.hostname.as112.net
   ;
   $TTL    1W
   @       SOA     server.example.net. admin.example.net. (
                           1               ; serial number
                           1W              ; refresh
                           1M              ; retry
                           1W              ; expire
                           1W )            ; negative caching TTL
   ;
           NS      blackhole-1.iana.org.
           NS      blackhole-2.iana.org.
   ;
           TXT     "Name of Facility or similar" "City, Country"
           TXT     "See http://www.as112.net/ for more information."
           TXT     "Unique IP: 203.0.113.1."
   ;
           LOC     45 25 0.000 N 75 42 0.000 W 80.00m 1m 10000m 10m

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   ; db.hostname.as112.arpa
   ;
   $TTL    1W
   @       SOA     server.example.net. admin.example.net. (
                           1               ; serial number
                           1W              ; refresh
                           1M              ; retry
                           1W              ; expire
                           1W )            ; negative caching TTL
   ;
           NS      blackhole.as112.arpa.
   ;
           TXT     "Name of Facility or similar" "City, Country"
           TXT     "See http://www.as112.net/ for more information."
   ;
           LOC     45 25 0.000 N 75 42 0.000 W 80.00m 1m 10000m 10m

3.6.  Testing a Newly Installed Node

   The BIND9 tool "dig" can be used to retrieve the TXT resource records
   associated with the names "HOSTNAME.AS112.NET" and
   "HOSTNAME.AS112.ARPA", directed at one of the AS112 anycast
   nameserver addresses.  Continuing the example from above, the
   response received should indicate the identity of the AS112 node that
   responded to the query.  See Section 3.5 for more details about the
   resource records associated with "HOSTNAME.AS112.NET".

       % dig @prisoner.iana.org hostname.as112.net txt +short +norec
       "Name of Facility or similar" "City, Country"
       "See http://www.as112.net/ for more information."
       %

   If the response received indicates that a different node is being
   used, then there is probably a routing problem to solve.  If there is
   no response received at all, there might be a host or nameserver
   problem.  Judicious use of tools such as traceroute and consultation
   of BGP looking glasses might be useful in troubleshooting.

   Note that an appropriate set of tests for a new server will include
   queries sent from many different places within the expected service
   area of the node, using both UDP and TCP transport, and exercising
   all three AS112 anycast nameserver addresses.

Top      ToC       Page 16 
4.  Operations

4.1.  Monitoring

   AS112 nodes should be monitored to ensure that they are functioning
   correctly, just as with any other production service.  An AS112 node
   that stops answering queries correctly can cause failures and
   timeouts in unexpected places and can lead to failures in dependent
   systems that can be difficult to troubleshoot.

4.2.  Downtime

   An AS112 node that needs to go off-line (e.g., for planned
   maintenance or as part of the diagnosis of some problem) should stop
   advertising the AS112 service prefixes to its BGP peers.  This can be
   done by shutting down the routing software on the node altogether or
   by causing the routing system to withdraw the route.

   Withdrawing the service prefixes is important in order to avoid
   blackholing query traffic in the event that the DNS software on the
   node is not functioning normally.

4.3.  Statistics and Measurement

   Use of the AS112 node should be measured in order to track long-term
   trends, identify anomalous conditions, and ensure that the
   configuration of the AS112 node is sufficient to handle the query
   load.

   Examples of free monitoring tools that might be useful to operators
   of AS112 nodes include:

   o  bindgraph <http://www.linux.it/~md/software/>

   o  dnstop <http://dns.measurement-factory.com/tools/dnstop/>

   o  DSC <https://www.dns-oarc.net/tools/dsc/>

   Operators of AS112 nodes should also consider participating in
   collection events as part of a larger, coordinated effort to gather
   important baselines.  One example of such an effort is Day in the
   Life <https://www.dns-oarc.net/oarc/data/ditl/>, coordinated by the
   DNS-OARC <https://www.dns-oarc.net/>.

Top      ToC       Page 17 
5.  Communications

   It is good operational practice to notify the community of users that
   may fall within the reach of a new AS112 node before it is installed.
   At Internet Exchanges, local mailing lists usually exist to
   facilitate such announcements.

   For nodes that are intended to be globally reachable, coordination
   with other AS112 operators is especially recommended.  The mailing
   list <as112-ops@lists.dns-oarc.net> is operated for this purpose.

   Information pertinent to AS112 operations is maintained at
   <http://www.as112.net/>.

   Information about an AS112 node should also be published within the
   DNS, within the "HOSTNAME.AS112.NET" and "HOSTNAME.AS112.ARPA" zones.
   See Section 3.5 for more details.

   AS112 operators should also be aware of the measures described in
   [RFC6305] and direct site administrators appropriately.

6.  On the Future of AS112 Nodes

   It is recommended practice for the operators of recursive nameservers
   to answer queries for zones served by AS112 nodes locally, such that
   queries never have an opportunity to reach AS112 servers [RFC6303].
   Operational experience with AS112 nodes does not currently indicate
   an observable trend towards compliance with those recommendations,
   however.

   It is expected that some DNS software vendors will include default
   configuration that will implement measures such as those described in
   [RFC6303].  If such software is widely deployed, it is reasonable to
   assume that the query load received by AS112 nodes will decrease;
   however, it is safe to assume that the query load will not decrease
   to zero, and consequently that AS112 nodes will continue to provide a
   useful service for the foreseeable future.

   The use of DNAME redirection to provide AS112 service is new and
   hence is informed by minimal operational experience.  The use of
   DNAME means that queries for many source zones could be redirected to
   AS112 infrastructure with no real opportunity for coordination.

   If the DNAME redirection approach is successful, and in the absence
   of any operational concerns, the community might well recommend the
   retirement of the original Direct Delegation AS112 service.  This
   document makes no such recommendation, however.

Top      ToC       Page 18 
7.  IANA Considerations

7.1.  General

   The nameservers associated with Direct Delegation AS112 service are
   all named under the domain IANA.ORG (see Section 2.3).  However, the
   anycast infrastructure itself is operated by a loosely coordinated,
   diverse mix of organisations across the Internet and is not an IANA
   function.

   The autonomous system number 112, the IPv4 prefix 192.175.48.0/24,
   and the IPv6 prefix 2620:4f:8000::/48 were assigned by ARIN.

   The IPv4 prefix 192.31.196.0/24 and the IPv6 prefix 2001:4:112::/48,
   used for DNAME redirection AS112 service, were assigned by the IANA
   [RFC7535].

   The three nameservers BLACKHOLE-1.IANA.ORG, BLACKHOLE-2.IANA.ORG, and
   PRISONER.IANA.ORG are also reachable over IPv6, as described in
   Section 2.3.  Following a substantial period of pre-production
   testing by AS112 operators, the IANA has added AAAA RRSets to those
   owner names in Section 7.2.1, to allow the servers to receive queries
   and generate responses over IPv6 transport.

7.2.  IANA Actions

7.2.1.  IPv6 Transport for Direct Delegation AS112 Servers

   The IANA has added the following AAAA resource records for the three
   Direct Delegation AS112 nameservers named under IANA.ORG:

                +----------------------+------------------+
                | Owner Name           | AAAA RDATA       |
                +----------------------+------------------+
                | PRISONER.IANA.ORG    | 2620:4f:8000::1  |
                |                      |                  |
                | BLACKHOLE-1.IANA.ORG | 2620:4f:8000::6  |
                |                      |                  |
                | BLACKHOLE-2.IANA.ORG | 2620:4f:8000::42 |
                +----------------------+------------------+

Top      ToC       Page 19 
7.2.2.  Registration in the Special-Purpose AS Numbers Registry

   The IANA has added AS112 to the "Special-Purpose AS Numbers" registry
   specified in [RFC7249] as follows:

   AS Numbers:  112

   Reason for Reservation:  Used by the AS112 project to sink
      misdirected DNS queries; see RFC 7534.

7.2.3.  Registration in the IANA IPv4 Special-Purpose Address Registry

   The IANA has added 192.175.48.0/24 to the "IANA IPv4 Special-Purpose
   Address Registry" specified in [RFC6890] as follows:

   Address Block:  192.175.48.0/24

   Name:  Direct Delegation AS112 Service

   RFC:  RFC 7534

   Allocation Date:  1996-01

   Termination Date:  N/A

   Source:  True

   Destination:  True

   Forwardable:  True

   Global:  True

   Reserved-by-Protocol:  False

7.2.4.  Registration in the IANA IPv6 Special-Purpose Address Registry

   The IANA has added 2620:4f:8000::/48 to the "IANA IPv6 Special-
   Purpose Address Registry" specified in [RFC6890] as follows:

   Address Block:  2620:4f:8000::/48

   Name:  Direct Delegation AS112 Service

   RFC:  RFC 7534

   Allocation Date:  2011-05

Top      ToC       Page 20 
   Termination Date:  N/A

   Source:  True

   Destination:  True

   Forwardable:  True

   Global:  True

   Reserved-by-Protocol:  False

8.  Security Considerations

   Hosts should never normally send queries to AS112 servers; queries
   relating to private-use addresses should be answered locally within a
   site.  Hosts that send queries to AS112 servers may well leak
   information relating to private infrastructure to the public network,
   and this could present a security risk.  Additionally, AS112
   operators may log this information, making it further subject to
   whatever security and privacy risks that might entail.  These risks
   are orthogonal to the presence or absence of authoritative servers
   for these zones in the public DNS infrastructure, however.

   Queries that are answered by AS112 servers are usually unintentional;
   it follows that the responses from AS112 servers are usually
   unexpected.  Unexpected inbound traffic can trigger intrusion
   detection systems or alerts by firewalls.  Operators of AS112 servers
   should be prepared to be contacted by operators of remote
   infrastructure who believe their security has been violated.  Advice
   to those who mistakenly believe that responses from AS112 nodes
   constitute an attack on their infrastructure can be found in
   [RFC6305].

   The deployment of AS112 nodes is very loosely coordinated compared to
   other services distributed using anycast.  The malicious compromise
   of an AS112 node and subversion of the data served by the node are
   hence more difficult to detect due to the lack of central management.
   Since it is conceivable that changing the responses to queries
   received by AS112 nodes might influence the behaviour of the hosts
   sending the queries, such a compromise might be used as an attack
   vector against private infrastructure.

   Operators of AS112 should take appropriate measures to ensure that
   AS112 nodes are appropriately protected from compromise, such as
   would normally be employed for production nameserver or network
   infrastructure.  The guidance provided for root nameservers in
   [RFC2870] may be instructive.

Top      ToC       Page 21 
   The zones hosted by AS112 servers are not signed with DNSSEC
   [RFC4033].  Given the distributed and loosely coordinated structure
   of the AS112 service, the zones concerned could only be signed if the
   private key material used was effectively public, obviating any
   security benefit resulting from the use of those keys.

9.  References

9.1.  Normative References

   [RFC1034]  Mockapetris, P., "Domain names - concepts and facilities",
              STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
              <http://www.rfc-editor.org/info/rfc1034>.

   [RFC1918]  Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G.,
              and E. Lear, "Address Allocation for Private Internets",
              BCP 5, RFC 1918, DOI 10.17487/RFC1918, February 1996,
              <http://www.rfc-editor.org/info/rfc1918>.

   [RFC2870]  Bush, R., Karrenberg, D., Kosters, M., and R. Plzak, "Root
              Name Server Operational Requirements", BCP 40, RFC 2870,
              DOI 10.17487/RFC2870, June 2000,
              <http://www.rfc-editor.org/info/rfc2870>.

   [RFC4033]  Arends, R., Austein, R., Larson, M., Massey, D., and S.
              Rose, "DNS Security Introduction and Requirements",
              RFC 4033, DOI 10.17487/RFC4033, March 2005,
              <http://www.rfc-editor.org/info/rfc4033>.

   [RFC4271]  Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
              Border Gateway Protocol 4 (BGP-4)", RFC 4271,
              DOI 10.17487/RFC4271, January 2006,
              <http://www.rfc-editor.org/info/rfc4271>.

   [RFC4786]  Abley, J. and K. Lindqvist, "Operation of Anycast
              Services", BCP 126, RFC 4786, DOI 10.17487/RFC4786,
              December 2006, <http://www.rfc-editor.org/info/rfc4786>.

   [RFC7535]  Abley, J., Dickson, B., Kumari, W., and G. Michaelson,
              "AS112 Redirection Using DNAME", RFC 7535,
              DOI 10.17487/RFC7535, May 2015,
              <http://www.rfc-editor.org/info/rfc7535>.

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9.2.  Informative References

   [RFC1876]  Davis, C., Vixie, P., Goodwin, T., and I. Dickinson, "A
              Means for Expressing Location Information in the Domain
              Name System", RFC 1876, DOI 10.17487/RFC1876, January
              1996, <http://www.rfc-editor.org/info/rfc1876>.

   [RFC5001]  Austein, R., "DNS Name Server Identifier (NSID) Option",
              RFC 5001, DOI 10.17487/RFC5001, August 2007,
              <http://www.rfc-editor.org/info/rfc5001>.

   [RFC5855]  Abley, J. and T. Manderson, "Nameservers for IPv4 and IPv6
              Reverse Zones", BCP 155, RFC 5855, DOI 10.17487/RFC5855,
              May 2010, <http://www.rfc-editor.org/info/rfc5855>.

   [RFC6303]  Andrews, M., "Locally Served DNS Zones", BCP 163,
              RFC 6303, DOI 10.17487/RFC6303, July 2011,
              <http://www.rfc-editor.org/info/rfc6303>.

   [RFC6304]  Abley, J. and W. Maton, "AS112 Nameserver Operations",
              RFC 6304, DOI 10.17487/RFC6304, July 2011,
              <http://www.rfc-editor.org/info/rfc6304>.

   [RFC6305]  Abley, J. and W. Maton, "I'm Being Attacked by
              PRISONER.IANA.ORG!", RFC 6305, DOI 10.17487/RFC6305,
              July 2011, <http://www.rfc-editor.org/info/rfc6305>.

   [RFC6672]  Rose, S. and W. Wijngaards, "DNAME Redirection in the
              DNS", RFC 6672, DOI 10.17487/RFC6672, June 2012,
              <http://www.rfc-editor.org/info/rfc6672>.

   [RFC6890]  Cotton, M., Vegoda, L., Bonica, R., Ed., and B. Haberman,
              "Special-Purpose IP Address Registries", BCP 153,
              RFC 6890, DOI 10.17487/RFC6890, April 2013,
              <http://www.rfc-editor.org/info/rfc6890>.

   [RFC7249]  Housley, R., "Internet Numbers Registries", RFC 7249,
              DOI 10.17487/RFC7249, May 2014,
              <http://www.rfc-editor.org/info/rfc7249>.

Top      ToC       Page 23 
Appendix A.  A Brief History of AS112

   Widespread use of the private address blocks listed in [RFC1918]
   followed that document's publication in 1996.  At that time, the
   IN-ADDR.ARPA zone was served by root servers.

   The idea of offloading IN-ADDR.ARPA queries relating to [RFC1918]
   addresses from the root nameservers was first proposed by Bill
   Manning and John Brown.

   The use of anycast for distributing authoritative DNS service for
   [RFC1918] IN-ADDR.ARPA zones was subsequently proposed at a private
   meeting of root server operators.

   ARIN provided an IPv4 prefix for the anycast service and also the
   autonomous system number 112 for use in originating that prefix.
   This assignment gave the project its name.

   In 2002, the first AS112 anycast nodes were deployed.

   In 2011, the IN-ADDR.ARPA zone was redelegated from the root servers
   to a new set of servers operated independently by AfriNIC, APNIC,
   ARIN, ICANN, LACNIC, and the RIPE NCC and named according to
   [RFC5855].

   [RFC6304], the precursor to this document, was published in
   July 2011.

   The use of anycast nameservers in the AS112 project contributed to
   the operational experience of anycast DNS services, and it can be
   seen as a precursor to the anycast distribution of other
   authoritative DNS servers in subsequent years (e.g., various root
   servers).

Appendix B.  Changes since RFC 6304

   A number of changes and enhancements to the AS112 service has been
   introduced since the publication of [RFC6304].

   o  The addition of IPv6 transport.

   o  The extension of the AS112 service to include the ability to have
      additional zones delegated for sinking or removed using the DNAME
      resource record.

   o  Requisite changes to the guidance regarding the configuration of
      current and future AS112 nodes.

Top      ToC       Page 24 
   o  Further clarification about the leakage of information in the
      Security Considerations section.

   o  A direction to the IANA to register the AS112 project's prefixes
      in the IANA Special-Purpose Address registries.

Acknowledgements

   This document benefited from review and suggestions from Leo Vegoda
   and Pearl Liang.

   The authors wish to acknowledge the assistance of Bill Manning, John
   Brown, Marco D'Itri, Daniele Arena, Stephane Bortzmeyer, Frank
   Habicht, Chris Thompson, Peter Losher, Peter Koch, Alfred Hoenes, S.
   Moonesamy, Mehmet Akcin, and Aleksi Suhonen in the preparation of
   [RFC6304], which this document supersedes.

Authors' Addresses

   Joe Abley
   Dyn, Inc.
   103-186 Albert Street
   London, ON  N6A 1M1
   Canada

   Phone: +1 519 670 9327
   EMail: jabley@dyn.com


   William F. Maton Sotomayor
   Ottawa Internet Exchange
   Constitution Square
   1400-340 Albert Street
   Ottawa, ON  K1R 0A5
   Canada

   EMail: wfms@ottix.net