One document matched: draft-ietf-dnsop-as112-dname-01.xml
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<rfc category="info" ipr="trust200902"
docName="draft-ietf-dnsop-as112-dname-01"
updates="6304">
<?rfc toc="yes" ?>
<?rfc symrefs="yes" ?>
<?rfc sortrefs="yes"?>
<?rfc iprnotified="no" ?>
<?rfc strict="yes" ?>
<front>
<title>AS112 Redirection using DNAME</title>
<author initials='J.' surname="Abley" fullname='Joe Abley'>
<organization>Dyn, Inc.</organization>
<address>
<postal>
<street>470 Moore Street</street>
<city>London</city>
<region>ON</region>
<code>N6C 2C2</code>
<country>Canada</country>
</postal>
<phone>+1 519 670 9327</phone>
<email>jabley@dyn.com</email>
</address>
</author>
<author initials="B.P." surname="Dickson" fullname="Brian Dickson">
<organization>Verisign Labs</organization>
<address>
<postal>
<street>12061 Bluemont Way</street>
<city>Reston</city>
<region>VA</region>
<code>20190</code>
<country>USA</country>
</postal>
<email>bdickson@verisign.com</email>
</address>
</author>
<author initials="W." surname="Kumari" fullname="Warren Kumari">
<organization>Google</organization>
<address>
<postal>
<street>1600 Amphitheatre Parkway</street>
<city>Mountain View</city>
<region>CA</region>
<code>94043</code>
<country>USA</country>
</postal>
<email>warren@kumari.net</email>
</address>
</author>
<author initials="G." surname="Michaelson" fullname="George Michaelson">
<organization>APNIC</organization>
<address>
<email>ggm@apnic.net</email>
</address>
</author>
<date day="14" month="February" year="2014"/>
<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
IN-ADDR.ARPA authoritative servers. The AS112 project is
named after the Autonomous System Number (ASN) that was
assigned to it.</t>
<t>The AS112 project does not accommodate the addition and
removal of DNS zones elegantly. Since additional zones of
definitively local significance are known to exist, this
presents a problem. This document describes modifications
to the deployment and use of AS112 infrastructure that will
allow zones to be added and dropped much more easily.</t>
</abstract>
</front>
<middle>
<section title="Introduction">
<t>The AS112 project is described in detail in <xref
target="RFC6304"/>.</t>
<t>The AS112 nameservers (PRISONER.IANA.ORG,
BLACKHOLE-1.IANA.ORG and BLACKHOLE-2.IANA.ORG) are required
to answer authoritatively for each and every zone that is
delegated to them.</t>
<t>If a zone is delegated to AS112 nameservers without those
nameservers being configured ahead of time to answer
authoritatively for that zone, there is a detrimental impact
on clients following referrals for queries within that zone.
This misconfiguration is colloquially known as a "lame
delegation".</t>
<t>AS112 nameserver operators are only loosely-coordinated,
and hence adding support for a new zone (or, correspondingly,
removing support for a zone that is no longer delegated to
the AS112 nameservers) is difficult to accomplish with
accuracy; testing AS112 nameservers remotely to see whether
they are configured to answer authoritatively for a particular
zone is similarly challenging since AS112 nodes are distributed
using <xref target="RFC4786">anycast</xref>.</t>
<t>This document proposes a more flexibl approach for sinking
queries on AS112 infrastructure that can be deployed alongside
unmodified, existing AS112 nodes. Instead of delegating
additional zones directly to AS112 nameservers, <xref
target="RFC6672">DNAME</xref> redirection is used instead.
This approach has the advantage that query traffic for
arbitrary parts of the namespace can be directed to AS112
servers without those servers having to be reconfigured
every time a zone is added or removed.</t>
</section>
<section title="Design Overview">
<t>A new zone, EMPTY.AS112.ARPA, is delegated to a single
nameserver BLACKHOLE.AS112.ARPA (IPv4 address TBAv4-1, IPv6
address TBAv6-1).</t>
<t>The IPv4 address TBAv4-1 has been assigned by the IANA
such that the address is coverable by a single IPv4 /24
prefix, and that no other address covered by that prefix
is in use. The IPv6 address TBAv6-1 has been similarly
assigned such that no other address within a covering /48
is in use. This addressing plan accommodates the anycast
distribution of the BLACKHOLE.AS112.ARPA service using a
single IPv4 service prefix and a single IPv6 service prefix.
See <xref target="RFC4786"/> for more discussion of anycast
service distribution; see <xref target="iana"/> for the specific
requests this document makes of the IANA.</t>
<t>Some or all of the existing AS112 nodes should be extended
to support these new nameserver addresses, and to host the
EMPTY.AS112.ARPA zone. See <xref
target="I-D.jabley-dnsop-rfc6304bis"/> for revised guidance
to AS112 server operators.</t>
<t>Each part of the DNS namespace for which it is desirable to
sink queries at AS112 nameservers should be redirected to
the EMPTY.AS112.ARPA zone using <xref target="RFC6672">DNAME</xref>.
See <xref target="redirection"/> for guidance to zone
administrators.</t>
</section>
<section title="AS112 Operations">
<section title="Extensions to Support DNAME Redirection"
anchor="extensions">
<t>The guidance provided in <xref target="RFC6304"/> is
extended to include configuration of the TBAv4-1, and
TBAv6-1 addresses, and the corresponding announcement of
covering routes for those addresses, and to host the
EMPTY.AS112.ARPA zone.</t>
<t>IPv4-only AS112 nodes should only configure the TBAv4-1
nameserver address; IPv6-only AS112 nodes should only
configure the TBAv6-1 nameserver address.</t>
<t>It is only necessary for a single AS112 server operator
to implement these extensions for this mechanism to
function as intended. It is beneficial if many more than
one AS112 server operators make these changes, however,
since that provides for greater distribution and capacity
for the nameservers serving the EMPTY.AS112.ARPA zone.
It is not necessary for all AS112 server operators to
make these changes for the mechanism to be viable.</t>
<t>Detailed instructions for the implementation of these
extensions is included in <xref
target="I-D.jabley-dnsop-rfc6304bis"/>.</t>
</section>
<section title="Redirection of Query Traffic to AS112 Servers"
anchor="redirection">
<t>Once the EMPTY.AS112.ARPA zone has been deployed using the
nameservers described in <xref target="extensions"/>,
redirections may be installed in the DNS namespace for
queries that are intended to be answered by the AS112
infrastructure.</t>
<t>For example, reverse queries corresponding to <xref
target="RFC5737">TEST-NET-1 (192.0.2.0/24)</xref> could
be redirected to AS112 nameservers by installing a DNAME
resource record in the 192.IN-ADDR.ARPA zone, as illustrated
in <xref target="TEST-NET-1"/>.</t>
<figure anchor="TEST-NET-1">
<artwork>
$ORIGIN 192.IN-ADDR.ARPA.
...
2.0.IN-ADDR.ARPA. IN DNAME EMPTY.AS112.ARPA.
...
</artwork>
</figure>
<t>There is no practical limit to the number of redirections
that can be configured in this fashion. Redirection of
a particular part of the namespace to EMPTY.AS112.ARPA
can be removed at any time, under the control of the
administrators of the corresponding part of the DNS
namespace. No changes to deployed AS112 nodes incorporating
the extensions described in this document are required
to support additional redirections. A list of possible
candidates for AS112 redirection can be found in <xref
target="candidates"/>.</t>
<t>DNAME resource records deployed for this purpose can be
signed with <xref target="RFC4033">DNSSEC</xref>, providing
a secure means of authenticating the legitimacy of each
redirection.</t>
</section>
</section>
<section title="Continuity of AS112 Operations">
<t>Existing guidance to AS112 server operators to accept and
respond to queries directed at the PRISONER.IANA.ORG,
BLACKHOLE-1.IANA.ORG and BLACKHOLE-2.IANA.ORG nameservers
should continue to be followed, and no changes to the
delegation of existing zones hosted on AS112 servers
should occur. These measures are intended to provide
continuity of operations for zones currently delegated to
AS112 servers and avoid any accidental client impact due
to the changes proposed in this document.</t>
<t>Once it has become empirically and quantitatively clear that
the EMPTY.AS112.ARPA zone is well-hosted to the extent that
it is thought that the existing, unmodified AS112 servers
host 10.IN-ADDR.ARPA, the decision might be made to replace
the delegation of those <xref target="RFC1918"/> zones with
DNAME redirection. Once implemented, the PRISONER.IANA.ORG,
BLACKHOLE-1.IANA.ORG and BLACKHOLE-2.IANA.ORG nameservers
could be retired. This document gives no such direction to
the IANA, however.</t>
</section>
<section title="Candidate Zones for AS112 Redirection"
anchor="candidates">
<t>All zones listed in <xref target="RFC6303"/> are candidates
for AS112 redirection.</t>
<t>Since no pre-provisioning is required on the part of AS112
operators to facilitate sinking of any name in the DNS namespace
by AS112 infrastructure, this mechanism supports AS112 redirection
by any zone owner in the DNS.</t>
<t>This document is simply concerned with provision of the
AS112 redirection service, and does not specify that any
particular AS112 redirection be put in place.</t>
</section>
<section title="DNAME Deployment Considerations">
<t>DNAME was specified a significant time following the original
implementations of <xref target="RFC1035"/>, and hence universal
deployment cannot be expected. <xref target="RFC6672"/> specifies
a fall-back mechanism which makes use of synthesised CNAME RRSets
for this reason. The expectation that design choices in the
DNAME specification ought to mitigate any lack of deployment is
reviewed below. Experimental validation of those expectations is
included in <xref target="experiment"/>.</t>
<t>It is a fundamental design requirement of AS112 service that
responses be cached. We can safely declare DNAME support on the
authoritative server to be a prerequisite for DNAME redirection,
but the cases where individual elements in resolver chains do
not support DNAME processing deserve closer examination.</t>
<t>The expected behaviour when a DNAME response is supplied to a
resolver that does not support DNAME is that the accompanying,
synthesised CNAME will be accepted and cached. Re-query
frequency will be determined by the TTLs returned by the
DNAME-responding authoritative servers.</t>
<t>Resolution of the CNAME target is straightforward and
functions exactly as the AS112 project has operated since
it was deployed. The <xref target="RFC2308">negative
caching</xref> of the CNAME target follows the parameters
defined in the target zone, EMPTY.AS112.ARPA. This has the
side-effects that all redirected names ultimately landing
on an AS112 node will be negatively-cached with the same
parameters, but this lack of flexibility seems non-controversial;
the effect of reducing the negative cache TTL would be
increased query volume on the AS112 node operator concerned,
and hence controls seem well-aligned with operation.</t>
<t>Validating resolvers (i.e. those requesting and processing
<xref target="RFC4033">DNSSEC</xref> metadata) are required
to implement DNAME, and hence should not make use of
synthesised CNAME RRs. The lack of signature over a received
CNAME RR should hence not limit the ability to sign the
redirection point, and for those signatures to be validated.</t>
<t>In the case where a recursive server implements DNAME, but
DNAME is not implemented in a stub resolver, CNAME synthesis
will again provide a viable path.</t>
<t>DNAME support on AS112 nodes themselves is never required
under this proposal.</t>
</section>
<section title="IAB Considerations">
<t>This document proposes a delegation within the ARPA domain,
and, in accordance with <xref target="RFC3172"/>, IAB review
and approval of the delegation of AS112.ARPA as described
in <xref target="iana"/> is required.</t>
<t>Once IAB approval has been obtained, this section may be
removed prior to publication or updated to include text that
confirms the IAB's decision, at the IAB's discretion.</t>
</section>
<section title="IANA Considerations" anchor="iana">
<section title="Address Assignment">
<t>The IANA is requested to assign one IPv4 /24 netblock
and one IPv6 /48 netblock that, to the best of their
knowledge, should be suitable for announcement as a single
IPv4 /24 prefix and a single IPv6 prefix on the global
Internet, respectively.</t>
<t>Once assigned, all occurrences of TBAv4 in this document
should be replaced by the IPv4 netblock assigned, in
conventional notation. Occurrences of TBAv4-1 should be
replaced with an address from the netblock with lowest
octet set to 1. Similarly, all occurrences of TBAv6 in
this document should be replaced by the IPv6 netblock
assigned, in conventional notation, and TBAv6-1 replaced
with an address from that netblock with the lowest 48
bits set to the value 1. Once those changes are made, this
paragraph may be removed prior to publication.</t>
<t>The netblocks assigned by the IANA for this purpose are
TBAv4 and TBAv6.</t>
</section>
<section title="Hosting of AS112.ARPA" anchor="hosting">
<t>The IANA is requested to host and sign the zone AS112.ARPA
using nameservers and DNSSEC signing infrastructure of their
choosing, as shown in <xref target="as112arpa"/>. SOA RDATA
may be adjusted by the IANA to suit their operational
requirements.</t>
<figure anchor="as112arpa">
<artwork>
$ORIGIN AS112.ARPA.
$TTL 3600
@ IN SOA BLACKHOLE.AS112.ARPA. NOC.DNS.ICANN.ORG. (
1 ; serial
10800 ; refresh
3600 ; retry
1209600 ; expire
3600 ) ; negative cache TTL
NS A.IANA-SERVERS.NET.
NS B.IANA-SERVERS.NET.
NS C.IANA-SERVERS.NET.
BLACKHOLE A TBAv4-1
AAAA TBAv6-1
HOSTNAME NS BLACKHOLE
EMPTY NS BLACKHOLE
</artwork>
</figure>
</section>
<section title="Delegation of AS112.ARPA">
<t>Once the AS112.ARPA zone is being hosted in production,
the IANA is requested to arrange delegation from the ARPA
zone according to normal IANA procedure for ARPA zone
management, to the nameservers used in carrying out the
direction in <xref target="hosting"/>. The following
metadata is suggested for the delegation, but may be
changed by the IANA if required:</t>
<texttable>
<ttcol>Name</ttcol>
<ttcol>Value</ttcol>
<c>Domain:</c>
<c>AS112.ARPA</c>
<c>Administrative Contact:</c>
<c>Internet Architecture Board (IAB) c/o IETF Administrative
Support Activity, ISOC</c>
<c>Technical Contact:</c>
<c>Internet Assigned Numbers Authority (IANA)</c>
<c>Nameservers:</c>
<c>As chosen by the IANA, see <xref target="hosting"/></c>
<c>DS-RDATA:</c>
<c>As chosen by the IANA, see <xref target="hosting"/></c>
</texttable>
</section>
</section>
<section title="Security Considerations">
<t>This document presents no known additional security concerns
to the Internet.</t>
<t>For security considerations relating to AS112 service in
general, see <xref target="RFC6304"/>.</t>
</section>
<section title="Acknowledgements">
<t>Your name here, etc.</t>
</section>
</middle>
<back>
<references title="Normative References">
&rfc1035;
&rfc2308;
&rfc6304;
&rfc6672;
<reference anchor="I-D.jabley-dnsop-rfc6304bis">
<front>
<title>AS112 Nameserver Operations</title>
<author initials="J." surname="Abley" fullname="Joe Abley"/>
<author initials="W." surname="Maton" fullname="William F. Maton Sotomayor"/>
<date month="February" day="13" year="2014"/>
</front>
<seriesInfo name="Internet-Draft" value="draft-jabley-dnsop-rfc6304bis-00"/>
<format type="TXT" target="http://www.ietf.org/internet-drafts/draft-jabley-dnsop-rfc6304bis-00.txt"/>
</reference>
</references>
<references title="Informative References">
&rfc1918;
&rfc3172;
&rfc4033;
&rfc4786;
&rfc5737;
&rfc6303;
</references>
<section title="Assessing Support for DNAME in the Real World"
anchor="experiment">
<t>To measure the extent to which the DNAME construct is
supported in the Internet, we have used an experimental
technique to test the DNS resolvers used by end hosts, and
derive from the test a measurement of DNAME support within
the Internet.</t>
<section title="Methodology">
<t>The test was conducted by loading a user's browser with
4 URLs to retrieve. The first three comprise the test
setup, while the final URL communicates the result the
the experiment controller. The URLs are:
<list style="hanging">
<t hangText="A">http://a.<unique_string>.dname.example.com/1x1.png?<vspace blankLines="0"/>a.<unique_string>.dname</t>
<t hangText="B">http://b.dname.example.com/1x1.png?<vspace blankLines="0"/>b.<unique_string>.dname</t>
<t hangText="C">http://c.<unique_string>.target.example.net/1x1.png?<vspace blankLines="0"/>c.<unique_string>.target</t>
<t hangText="D">http://results.recorder.example.net/1x1.png?<vspace blankLines="0"/>results.<unique_string>?za=<a_result>&zb=<b_result>&zc=<c_result>
</t>
</list>
</t>
<t>The A URL is designed to test the end users capability
to resolve a name that has never been seen before, so that
the resolution of this domain name will reliably result
in a query at the authoritative name server. This is
intended to test the use of domain names where there is
a dynamic component that also uses the DNAME construct.</t>
<t>The B URL is deliberately designed to be cached by caching
resolvers that are used in the process of resolving the
domain name.</t>
<t>The C URL is a control URL. This is a unique URL, similar
to A, but does not refer to a DNAME structure.</t>
<t>The D URL uses a static cacheable domain name.</t>
<t>The <unique_string> value is common to the four
URLs used in each individual instance of this test, but
varies from test to test. The result is that each end
user is presented with a unique string.</t>
<t>The contents of the EXAMPLE.COM, TARGET.EXAMPLE.NET and
RECORDER.EXAMPLE.NET zones are shown in
<xref target="experiment-zones"/>.</t>
<figure anchor="experiment-zones">
<artwork>
$ORIGIN EXAMPLE.COM.
...
DNAME. IN DNAME TARGET.EXAMPLE.NET.
...
$ORIGIN TARGET.EXAMPLE.NET.
...
B IN A 192.0.2.0
* IN A 192.0.2.0
...
$ORIGIN RECORDER.EXAMPLE.NET.
...
RESULTS IN A 192.0.2.0
...
</artwork>
</figure>
<t>The first three URLs (A, B and C) are loaded as tasks
into the user's browser upon execution of the test's
script. The script starts a timer with each of these
URLs to measure the elapsed time to fetch the URL. The
script then waits for the three fetches to complete, or
10 seconds, whichever occurs first. The script then loads
the results of the three timers into the GET arguments
of the D URL, and performs a fetch to pass these results
back to the experiment's server.</t>
<t>Logs on the web server reached at RESULTS.EXAMPLE.NET
will include entries of the form shown in <xref
target="experiment-results"/>. If any of the URLs fail
to load within 10 secords the D URL will report the failure
as a "null" timer value.</t>
<figure anchor="experiment-results">
<artwork>
GET /1x1.png?results.<unique_string>?za=1822&zb=1674&zc=1582
GET /1x1.png?results.<unique_string>?za=null&zb=null&zc=161
</artwork>
</figure>
<t>The script has been encoded in Adobe Flash with a simple
image in the form of an online advertisement. An online
advertisement network has been used to distribute the
script. The script is invoked when the advertisement is
presented in the end user's browser or application, and
does not require the user to click on the supplied image
in any way. The advertisement placement parameters were
set to to broadest possible scope to sample users from
across the entire internet.</t>
</section>
<section title="Results">
<t>The test was loaded into an advertisement distributed
on the 2013-10-10 and 2013-10-11.</t>
<texttable anchor="table_ex">
<ttcol align='left'> </ttcol>
<ttcol align='right'>Count</ttcol>
<ttcol align='right'>Percentage</ttcol>
<c>Recorded Results:</c><c>338,478</c><c></c>
<c>A or B Loaded:</c><c>331,896</c><c>98.1%</c>
<c>A Fail and B Fail:</c><c>6,492</c><c>1.9%</c>
<c>A Fail and B Load:</c><c>4,249</c><c>1.3%</c>
<c>A Load and B Fail:</c><c>1,624</c><c>0.5%</c>
<c>C Fail:</c><c>9,355</c><c>2.8%</c>
</texttable>
<t>These results indicate that at most 1.9% of tested
clients use DNS resolvers that fail to resolve a domain
name that contains a DNAME redirection. However the
failure rate of slightly lower than 3% for the control
URL indicates that the failure rate for the DNAME construct
lies within the bounds of error within the experimental
framework. We conclude that there is no evidence of a
consistent failure on the part of deployed DNS resolvers
to correctly resolve a DNAME construct.</t>
<t>This experiment was conducted by Geoff Huston and George
Michaelson.</t>
</section>
</section>
<section title="Editorial Notes">
<t>This section (and sub-sections) to be removed prior to
publication.</t>
<section title="Change History">
<t>
<list style="hanging">
<t hangText="00">Initial write-up of Brian's idea,
circulated for the purposes of entertainment.</t>
<t hangText="01">Some particularly egregious spelling
mistakes fixed. Warren Kumari and George Michaelson
added as co-authors. Intended status changed to
informational. Appendix on DNAME testing added,
describing an experiment conducted by Geoff Huston
and George Michaelson.</t>
<t hangText="00">Adopted by dnsop in IETF88, Vancouver;
resubmitted as draft-ietf-dnsop-as112-dname. Changed
contact info for Brian.</t>
<t hangText="01">Minor updates following submission of
<xref target="I-D.jabley-dnsop-rfc6304bis"/>.</t>
</list>
</t>
</section>
</section>
</back>
</rfc>
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