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RFC 6304

AS112 Nameserver Operations

Pages: 18
Obsoleted by:  7534

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Internet Engineering Task Force (IETF)                          J. Abley
Request for Comments: 6304                                         ICANN
Category: Informational                                         W. Maton
ISSN: 2070-1721                                                 NRC-CNRC
                                                               July 2011


                      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 IN-ADDR.ARPA 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. 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.
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   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/rfc6304.

Copyright Notice

   Copyright (c) 2011 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.

   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
   material may not have granted the IETF Trust the right to allow
   modifications of such material outside the IETF Standards Process.
   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
   outside the IETF Standards Process, and derivative works of it may
   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.
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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. AS112 DNS Service . . . . . . . . . . . . . . . . . . . . . . 4 2.1. Zones . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.2. Nameservers . . . . . . . . . . . . . . . . . . . . . . . 4 3. Installation of a New Node . . . . . . . . . . . . . . . . . . 5 3.1. Useful Background Knowledge . . . . . . . . . . . . . . . 5 3.2. Topological Location . . . . . . . . . . . . . . . . . . . 5 3.3. Operating System and Host Considerations . . . . . . . . . 5 3.4. Routing Software . . . . . . . . . . . . . . . . . . . . . 6 3.5. DNS Software . . . . . . . . . . . . . . . . . . . . . . . 8 3.6. Testing a Newly Installed Node . . . . . . . . . . . . . . 11 4. Operations . . . . . . . . . . . . . . . . . . . . . . . . . . 12 4.1. Monitoring . . . . . . . . . . . . . . . . . . . . . . . . 12 4.2. Downtime . . . . . . . . . . . . . . . . . . . . . . . . . 12 4.3. Statistics and Measurement . . . . . . . . . . . . . . . . 12 5. Communications . . . . . . . . . . . . . . . . . . . . . . . . 12 6. On the Future of AS112 Nodes . . . . . . . . . . . . . . . . . 13 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 8. Security Considerations . . . . . . . . . . . . . . . . . . . 14 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 14 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15 10.1. Normative References . . . . . . . . . . . . . . . . . . . 15 10.2. Informative References . . . . . . . . . . . . . . . . . . 15 Appendix A. History . . . . . . . . . . . . . . . . . . . . . . . 17

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].
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   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.

2. AS112 DNS Service

2.1. Zones

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 [RFC5735]: o 254.169.IN-ADDR.ARPA To aid identification of AS112 anycast nodes, each node also answers authoritatively for the zone HOSTNAME.AS112.NET. See Section 3.5 for the recommended contents of all these zones. It is possible that other zones corresponding to private-use infrastructure will be delegated to AS112 servers in the future. A list of zones for which AS112 servers answer authoritatively is maintained at <http://www.as112.net/>.

2.2. Nameservers

The zones listed in Section 2.1 are delegated to the two nameservers BLACKHOLE-1.IANA.ORG (192.175.48.6) and BLACKHOLE-2.IANA.ORG (192.175.48.42). Additionally, the server PRISONER.IANA.ORG (192.175.48.1) 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.
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   The addresses of all these nameservers are covered by the single IPv4
   prefix 192.175.48.0/24.

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. 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 2.2 will be configured on these interfaces in order that the DNS software can respond to queries properly.
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   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 prefix 192.175.48.0/24 to the Internet with origin AS 112 (see also Section 2.2). The examples in this document are based on the Quagga Routing Suite [QUAGGA] 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 and 192.0.2.2. Note the local AS number is 112, and the service prefix originated from the AS112 node is 192.175.48.0/24.
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   ! 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 prefix 192.175.48.0/24.
   ! All other addresses shown below are illustrative, and
   ! actual numbers will depend on local circumstances.
   !
   router bgp 112
    bgp router-id 203.0.113.1
    network 192.175.48.0
    neighbor 192.0.2.1 remote-as 64496
    neighbor 192.0.2.1 next-hop-self
    neighbor 192.0.2.1 prefix-list AS112 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 out
    neighbor 192.0.2.2 filter-list 1 out
   !
   ip prefix-list AS112 permit 192.175.48.0/24
   !
   ip as-path access-list 1 permit ^$

   The configuration above includes a double-blinded restriction on what
   the AS112 node shall advertise to the pair of BGP neighbors.
   Firstly, that prefix-list "AS112" only containing the service prefix
   192.175.48.0/24 shall be advertised.  Secondly, the "ip as-path
   access-list 1" statement contains a one-line regular expression that
   permits only the local AS number (112 in this case) and no other to
   be advertised as well.  Both statements prevent the node from
   becoming a transit router.  Equivalent restrictions using other BGP
   implementations should be utilised.

   The "zebra.conf" file is required to provide integration between
   protocol daemons (bgpd, in this case) and the kernel.
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   ! zebra.conf
   !
   hostname as112
   password <something>
   enable password <supersomething>
   !
   interface lo
   !
   interface eth0
   !

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 DNS software. Examples in this document are based on ISC BIND9 [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. // 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 correspond to AS112 addresses, 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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     };
     directory "/var/named";
     recursion no;        // authoritative-only server
     query-source address *;
   };

   // 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
   // has the potential to create high CPU load and consume
   // enormous amounts of disk space.

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

   // RFC 1918

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

   // RFC 5735

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

   // Also answer authoritatively for the HOSTNAME.AS112.NET zone,
   // which contains data of operational relevance.
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   zone "hostname.as112.net" {
     type master;
     file "db.hostname.as112.net";
   };

   The "db.empty" file follows, below.  This is the source data used to
   populate all the IN-ADDR.ARPA zones listed in Section 2.1.  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.empty
   ;
   ; Empty zone for AS112 server.
   ;
   $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.hostname.as112.net" file follows, below.  This zone contains
   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 response to the query
   "HOSTNAME.AS112.NET IN TXT" should fit within a 512-octet DNS/UDP
   datagram: i.e., it should be available over UDP transport without
   requiring EDNS0 support.

   The optional LOC record [RFC1876] included in the zone apex provides
   information about the geospatial location of the node.
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   ; 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-2.iana.org.
           NS      blackhole-1.iana.org.
   ;
           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 domain "HOSTNAME.AS112.NET", 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 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.
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4. Operations

4.1. Monitoring

AS112 nodes should be monitored to ensure 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 prefix 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 prefix 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 [BINDGRAPH] o dnstop [DNSTOP] o DSC [DSC]

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.
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   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" zone.  See Section 3.5 for more
   details.

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. There may be a requirement in the future for AS112 nodes to answer for their current set of zones over IPv6 transport. Such a requirement would necessitate the assignment of a corresponding IPv6 netblock for use as an anycast service prefix. There may be a requirement in the future for AS112 nodes to serve additional zones or to stop serving particular zones that are currently served. Such changes would be widely announced in operational forums and published at <http://www.as112.net/>.

7. IANA Considerations

The AS112 nameservers are all named under the domain IANA.ORG (see Section 2.2). 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 and the IPv4 prefix 192.175.48.0/24 were assigned by ARIN.
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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. This risk is 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. 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. Acknowledgements

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, and Mehmet Akcin in the preparation of this document.
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10. References

10.1. Normative References

[RFC1034] Mockapetris, P., "Domain names - concepts and facilities", STD 13, RFC 1034, November 1987. [RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and E. Lear, "Address Allocation for Private Internets", BCP 5, RFC 1918, February 1996. [RFC2870] Bush, R., Karrenberg, D., Kosters, M., and R. Plzak, "Root Name Server Operational Requirements", BCP 40, RFC 2870, June 2000. [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose, "DNS Security Introduction and Requirements", RFC 4033, March 2005. [RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway Protocol 4 (BGP-4)", RFC 4271, January 2006. [RFC4786] Abley, J. and K. Lindqvist, "Operation of Anycast Services", BCP 126, RFC 4786, December 2006.

10.2. Informative References

[BIND] Internet Systems Consortium, "BIND", <http://www.isc.org/software/BIND/>. [BINDGRAPH] Delaurenti, M. and M. d'Itri, "bindgraph", <http://www.linux.it/~md/software/>. [DNSTOP] The Measurement Factory, "Dnstop: Stay on Top of Your DNS Traffic", <http://dns.measurement-factory.com/tools/dnstop/>. [DSC] The Measurement Factory, "Dsc: A DNS Statistics Collector", <http://dns.measurement-factory.com/tools/dsc/>. [QUAGGA] "Quagga Software Routing Suite", <http://www.quagga.net>. [RFC1876] Davis, C., Vixie, P., Goodwin, T., and I. Dickinson, "A Means for Expressing Location Information in the Domain Name System", RFC 1876, January 1996.
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   [RFC5735]    Cotton, M. and L. Vegoda, "Special Use IPv4 Addresses",
                BCP 153, RFC 5735, January 2010.

   [RFC5855]    Abley, J. and T. Manderson, "Nameservers for IPv4 and
                IPv6 Reverse Zones", BCP 155, RFC 5855, May 2010.

   [RFC6303]    Andrews, M., "Locally Served DNS Zones", BCP 163,
                RFC 6303, July 2011.

   [RFC6305]    Abley, J. and W. Maton, "I'm Being Attacked by
                PRISONER.IANA.ORG!", RFC 6305, July 2011.
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Appendix A. History

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 off-loading 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]. 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).
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Authors' Addresses

Joe Abley ICANN 4676 Admiralty Way, Suite 330 Marina del Rey, CA 90292 US Phone: +1 519 670 9327 EMail: joe.abley@icann.org William F. Maton Sotomayor National Research Council of Canada 1200 Montreal Road Ottawa, ON K1A 0R6 Canada Phone: +1 613 993 0880 EMail: wmaton@ryouko.imsb.nrc.ca