One document matched: draft-ietf-dnsop-as112-ops-07.xml
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<rfc category="info" ipr="pre5378Trust200902"
docName="draft-ietf-dnsop-as112-ops-07">
<?rfc toc="yes" ?>
<?rfc symrefs="yes" ?>
<?rfc sortrefs="yes"?>
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<?rfc strict="yes" ?>
<front>
<title>AS112 Nameserver Operations</title>
<author initials='J.' surname="Abley" fullname='Joe Abley'>
<organization>ICANN</organization>
<address>
<postal>
<street>4676 Admiralty Way, Suite 330</street>
<city>Marina del Rey</city>
<region>CA</region>
<code>90292</code>
<country>US</country>
</postal>
<phone>+1 519 670 9327</phone>
<email>joe.abley@icann.org</email>
</address>
</author>
<author initials='W.' surname="Maton" fullname='William F. Maton Sotomayor'>
<organization abbrev="NRC-CNRC">National Research Council
of Canada</organization>
<address>
<postal>
<street>1200 Montreal Road</street>
<city>Ottawa</city>
<region>ON</region>
<code>K1A 0R6</code>
<country>Canada</country>
</postal>
<phone>+1 613 993 0880</phone>
<email>wmaton@ryouko.imsb.nrc.ca</email>
</address>
</author>
<date day="27" month="April" year="2011"/>
<abstract>
<t>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.</t>
<t>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.</t>
<t>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 root
and IN-ADDR.ARPA authoritative servers. The AS112 project is
named after the Autonomous System Number (ASN) that was
assigned to it.</t>
<t>This document describes the steps required to install
a new AS112 node, and offers advice relating to such a node's
operation.</t>
</abstract>
</front>
<middle>
<section title="Introduction">
<t>Many sites connected to the Internet make use of IPv4
addresses that are not globally unique. Examples are the
addresses designated in <xref target="RFC1918"/> for private
use within individual sites.</t>
<t>Devices in such environments may occasionally originate
Domain Name System (DNS) <xref target="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
<xref target="I-D.ietf-dnsop-default-local-zones"/>.
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.</t>
<t>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
root and IN-ADDR.ARPA authoritative servers.</t>
<t>The AS112 project encompasses a loosely coordinated
collection of independently operated nameservers. Each
nameserver functions as a single node in an AS112 <xref
target="RFC4786">anycast cloud</xref>, and
is configured to answer authoritatively for a particular
set of nominated zones.</t>
<t>The AS112 project is named after the Autonomous System
Number (ASN) that was assigned to it.</t>
</section>
<section title="AS112 DNS Service">
<section title="Zones" anchor="zones">
<t>AS112 nameservers answer authoritatively for the following
zones, corresponding to <xref target="RFC1918"/> private-use
netblocks:
<list style="symbols">
<t>10.IN-ADDR.ARPA</t>
<t>16.172.IN-ADDR.ARPA, 17.172.IN-ADDR.ARPA, ...,
31.172.IN-ADDR.ARPA</t>
<t>168.192.IN-ADDR.ARPA</t>
</list>
and the following zone, corresponding to the "link local"
netblock 169.254.0.0/16 listed in <xref target="RFC5735"/>:
<list style="symbols">
<t>254.169.IN-ADDR.ARPA</t>
</list>
</t>
<t>To aid identification of AS112 anycast nodes, each
node also answers authoritatively for the zone
HOSTNAME.AS112.NET.</t>
<t>See <xref target="dns"/> for the recommended contents
of all these zones.</t>
<t>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 <eref
target="http://www.as112.net/"/>.</t>
</section>
<section title="Nameservers" anchor="nameservers">
<t>The zones listed in <xref target="zones"/> are delegated to
the two nameservers BLACKHOLE-1.IANA.ORG (192.175.48.6)
and BLACKHOLE-2.IANA.ORG (192.175.48.42).</t>
<t>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.</t>
<t>The addresses of all these nameservers are covered by
the single IPv4 prefix 192.175.48.0/24.</t>
</section>
</section>
<section title="Installation of a New Node">
<section title="Useful Background Knowledge">
<t>Installation of an AS112 node is relatively straightforward.
However, experience in the following general areas may
prove useful:
<list style="symbols">
<t>inter-domain routing with <xref
target="RFC4271">BGP</xref>;</t>
<t>DNS authoritative server operations;</t>
<t><xref target="RFC4786">anycast</xref> distribution
of DNS services.</t>
</list>
</t>
</section>
<section title="Topological Location">
<t>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.</t>
<t>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).</t>
<t>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 <xref target="communications"/>.</t>
</section>
<section title="Operating System and Host Considerations">
<t>Examples in this document are based on UNIX and UNIX-like
operating systems, but other operating systems exist which
are suitable for use in construction of an AS112 node.</t>
<t>The chosen platform should include support for either
cloned loopback interfaces, or the capability to bind
multiple addresses to a single loopback interface. The
addresses of the nameservers listed in <xref
target="nameservers"/> will be configured on these
interfaces in order that the DNS software can respond to
queries properly.</t>
<t>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.</t>
<t>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.</t>
<t>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 while
the DNS software is not running.</t>
</section>
<section title="Routing Software">
<t>AS112 nodes signal the availability of AS112 nameservers
to the Internet using <xref target="RFC4271">BGP</xref>:
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
<xref target="nameservers"/>).</t>
<t>The examples in this document are based on the
<eref target="http://www.quagga.net/">Quagga Routing Suite</eref>,
but other software packages exist which also provide suitable BGP
support for AS112 nodes.</t>
<t>The "bgpd.conf" file is used by Quagga's bgpd daemon, which
provides BGP protocol 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
112, and the origination of the prefix 192.175.48.0/24.</t>
<figure>
<artwork>
! 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 192.0.2.2 remote-as 64497
neighbor 192.0.2.2 next-hop-self
</artwork>
</figure>
<t>The "zebra.conf" file is required to provide integration
between protocol daemons (bgpd, in this case) and the
kernel.</t>
<figure>
<artwork>
! zebra.conf
!
hostname as112
password <something>
enable password <supersomething>
!
interface lo
!
interface eth0
!
</artwork>
</figure>
</section>
<section title="DNS Software" anchor="dns">
<t>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 <xref
target="RFC1034">fully-functional
and standards-compliant DNS authoritative servers</xref>,
and hence require DNS software.</t>
<t>Suitable choices of free DNS software for AS112 nodes
include, but are not limited to:
<list style="symbols">
<t><eref target="http://www.isc.org/software/BIND/">ISC
BIND9</eref></t>
<t><eref target="http://www.nlnetlabs.nl/nsd/">NLnet Labs'
NSD</eref></t>
</list>
</t>
<t>Examples in this document are based on ISC BIND9.</t>
<t>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.</t>
<figure>
<artwork>
// 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)
};
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
zone "hostname.as112.net" {
type master;
file "db.hostname.as112.net";
};
</artwork>
</figure>
<t>The "db.empty" file follows, below. This is the source
data used to populate all the IN-ADDR.ARPA zones listed
in <xref target="zones"/>. Note that the RNAME specified
in the SOA record corresponds to hostmaster@root-servers.org,
a suitable e-mail address for receiving technical queries
about these zones.</t>
<figure>
<artwork>
; 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.
</artwork>
</figure>
<t>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, and 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.</t>
<t>The optional <xref target="RFC1876">LOC record</xref>
included in the zone apex provides information about the
geospatial location of the node.</t>
<figure>
<artwork>
; 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
</artwork>
</figure>
</section>
<section title="Testing a Newly-Installed Node">
<t>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 <xref target="dns"/> for more details about the
resource records associated with "HOSTNAME.AS112.NET".</t>
<figure>
<artwork>
% 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."
%
</artwork>
</figure>
<t>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 host
or nameserver problem. Judicious use of tools such as
traceroute, and consultation of BGP looking glasses might
be useful in troubleshooting.</t>
<t>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.</t>
</section>
</section>
<section title="Operations">
<section title="Monitoring">
<t>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.</t>
</section>
<section title="Downtime">
<t>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.</t>
<t>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.</t>
</section>
<section title="Statistics and Measurement">
<t>Use of the AS112 node should be measured in order to track
long-term trends, identify anomalous conditions, and to ensure
that the configuration of the AS112 node is sufficient to handle
the query load.</t>
<t>Examples of free monitoring tools that might be useful to
operators of AS112 nodes include, but are not limited to:
<list style="symbols">
<t><eref target="http://www.linux.it/~md/software/">bindgraph</eref></t>
<t><eref target="http://dns.measurement-factory.com/tools/dnstop/">dnstop</eref></t>
<t><eref target="http://dns.measurement-factory.com/tools/dsc/">DSC</eref></t>
</list>
</t>
</section>
</section>
<section title="Communications" anchor="communications">
<t>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.</t>
<t>For nodes that are intended to be globally reachable,
coordination with other AS112 operators is especially
recommended. The mailing list <eref
target="mailto:as112-ops@lists.dns-oarc.net"/> is operated
for this purpose.</t>
<t>Information pertinent to AS112 operations is maintained
at <eref target="http://www.as112.net/"/>.</t>
<t>Information about an AS112 node should also be published within
the DNS, within the "HOSTNAME.AS112.NET" zone. See
<xref target="dns"/> for more details.</t>
</section>
<section title="On the Future of AS112 Nodes">
<t>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 <xref
target="I-D.ietf-dnsop-default-local-zones"/>. Operational
experience with AS112 nodes does not currently indicate an
observable trend towards compliance with those recommendations,
however.</t>
<t>It is expected that some DNS software vendors will include
default configuration that will implement measures such
as those described in <xref
target="I-D.ietf-dnsop-default-local-zones"/>. 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.</t>
<t>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.</t>
<t>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 <eref target="http://www.as112.net/"/>.</t>
</section>
<section title="IANA Considerations">
<t>The AS112 nameservers are all named under the domain
IANA.ORG (see <xref target="nameservers"/>). However,
the anycast infrastructure itself is operated by a
loosely-coordinated, diverse mix of organisations across
the Internet, and is not an IANA function.</t>
<t>The autonomous system number 112 and the IPv4 prefix
192.175.48.0/24 were assigned by ARIN.</t>
<t>This document makes no request of the IANA.</t>
</section>
<section title="Security Considerations">
<t>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.</t>
<t>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
constitutes an attack on their infrastructure can be found
in <xref
target="I-D.ietf-dnsop-as112-under-attack-help-help"/>.</t>
<t>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 is 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.</t>
<t>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 <xref target="RFC2870"/> may be
instructive.</t>
<t>The zones hosted by AS112 servers are not signed with
DNSSEC <xref target="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.</t>
</section>
<section title="Acknowledgements">
<t>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 and Alfred Hoenes in the preparation of this
document.</t>
</section>
</middle>
<back>
<references title="Normative References">
&rfc1034;
&rfc1918;
&rfc2870;
&rfc4033;
&rfc4271;
&rfc4786;
</references>
<references title="Informative References">
&rfc1876;
&rfc5735;
&draft-ietf-dnsop-default-local-zones;
&draft-ietf-dnsop-as112-under-attack-help-help;
</references>
<section title="History">
<t>Widespread use of the private address blocks listed in
<xref target="RFC1918"/> followed that document's publication
in 1996.</t>
<t>The idea of off-loading IN-ADDR.ARPA queries relating to
<xref target="RFC1918"/> addresses from the root nameservers
was first proposed by Bill Manning and John Brown.</t>
<t>The use of anycast for distributing authoritative DNS
service for <xref target="RFC1918"/> IN-ADDR.ARPA zones was
subsequently proposed at a private meeting of root server
operators.</t>
<t>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.</t>
<t>In 2002, the first AS112 anycast nodes were deployed.</t>
<t>The use of anycast nameservers in the AS112 project
contributed to the operational experience of anycast DNS
services, and can be seen as a precursor to the anycast
distribution of other authoritative DNS servers in subsequent
years (e.g. various root servers).</t>
</section>
<section title="Change History">
<t>This section to be removed prior to publication.</t>
<t>
<list style="hanging">
<t hangText="00">Initial draft, circulated as
draft-jabley-as112-ops-00 and reviewed at the
DNSOP working group meeting at IETF 66.</t>
<t hangText="00">Document adoped by the DNSOP working
group and renamed accordingly.</t>
<t hangText="01">Input from reviewers of DNSOP and
others, some cosmetic tweaks.</t>
<t hangText="02">Version bump as request by DNSOP chairs.
Added missing IANA Considerations section. Updated
author's addresses. Make http://www.as112.net/ URL
consistent.</t>
<t hangText="03">Fix BLACKHOLE-2.IANA.ORG IP address.</t>
<t hangText="04">Bump version number. Refresh references.
Add reference to BIRD. Minor wordsmithing.</t>
<t hangText="05">Updated following review from Peter Koch.</t>
<t hangText="06">Updated following review from Alfred Hoenes.</t>
</list>
</t>
</section>
</back>
</rfc>
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