Network Working Group J. Abley
Internet-Draft T. Manderson
Intended status: Standards Track ICANN
Expires: June 12, 2010 December 9, 2009
Nameservers for IPv4 and IPv6 Reverse Zones
draft-jabley-reverse-servers-01
Abstract
This document specifies a stable naming scheme for the nameservers
which serve the zones IN-ADDR.ARPA and IP6.ARPA in the DNS. These
zones contain data which facilitate reverse mapping (address to
name).
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Nameservers for IN-ADDR.ARPA . . . . . . . . . . . . . . . . . 4
3. Nameservers for IP6.ARPA . . . . . . . . . . . . . . . . . . . 5
4. IAB Statement . . . . . . . . . . . . . . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
6. Security Considerations . . . . . . . . . . . . . . . . . . . 8
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
7.1. Normative References . . . . . . . . . . . . . . . . . . . 9
7.2. Informative References . . . . . . . . . . . . . . . . . . 9
Appendix A. Existing NS RRSets . . . . . . . . . . . . . . . . . 10
Appendix B. Performance Characteristics . . . . . . . . . . . . . 11
B.1. Label Compression . . . . . . . . . . . . . . . . . . . . 11
B.2. Query Patterns . . . . . . . . . . . . . . . . . . . . . . 13
B.2.1. QNAME under IN-ADDR.ARPA . . . . . . . . . . . . . . . 13
B.2.2. QNAME under IP6.ARPA . . . . . . . . . . . . . . . . . 14
Appendix C. Editorial Notes . . . . . . . . . . . . . . . . . . . 16
C.1. Change History . . . . . . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17
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1. Introduction
The Domain Name System (DNS) is described in [RFC1034] and [RFC1035].
The DNS currently supports keyed data retrieval using three
namespaces -- domain names, IPv4 addresses and IPv6 addresses.
Mapping of IPv4 addresses to names is accomplished using data
published in the IN-ADDR.ARPA zone. For IPv6, the IP6.ARPA zone is
used (see [RFC3152]). The process of mapping an address to a name is
generally known as a "reverse lookup", and the IN-ADDR.ARPA and
IP6.ARPA zones are said to support the "reverse DNS".
The secure and stable hosting of the IN-ADDR.ARPA and IP6.ARPA zones
is critical to the operation of the Internet, since many applications
rely upon timely responses to reverse lookups to be able to operate
normally.
At the time of writing, the IN-ADDR.ARPA zone is served by a subset
of the DNS root servers, and IP6.ARPA by servers operated by APNIC,
ARIN, ICANN, LACNIC and the RIPE NCC (see Appendix A).
This document specifies a dedicated and stable set of nameserver
names for each of the IN-ADDR.ARPA and IP6.ARPA zones.
The naming scheme specified in this document allows IN-ADDR.ARPA and
IP6.ARPA be delegated to two different sets of nameservers, to
facilitate operational separation of the infrastructure used to serve
each zone. This separation might help ensure that an operational
failure of IN-ADDR.ARPA servers does not impact IPv6 reverse lookups
as collateral damage, for example.
The choice of operators for individual nameservers is beyond the
scope of this document, and is an IANA function which falls under the
scope of section 4 of the MoU between the IETF and ICANN [RFC2860].
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2. Nameservers for IN-ADDR.ARPA
This document specifies the following naming scheme for servers which
host the IN-ADDR.ARPA zone:
A.IN-ADDR-SERVERS.ARPA
B.IN-ADDR-SERVERS.ARPA
C.IN-ADDR-SERVERS.ARPA
D.IN-ADDR-SERVERS.ARPA
E.IN-ADDR-SERVERS.ARPA
F.IN-ADDR-SERVERS.ARPA
...
The IN-ADDR-SERVERS.ARPA zone will be delegated to the same set of
servers as IN-ADDR.ARPA. IPv4 and IPv6 glue records for each of
those servers will be added to the ARPA zone.
The IN-ADDR-SERVERS.ARPA and IN-ADDR.ARPA zones are delegated to the
same servers since they are both dedicated for a single purpose and
hence can reasonably share fate.
All servers in the set are named under the same domain to facilitate
label compression. Since glue for all servers will exist in the ARPA
zone, the use of a single domain does not present a practical single
point of failure.
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3. Nameservers for IP6.ARPA
This document specifies the following nameserver set for the IP6.ARPA
zone:
A.IP6-SERVERS.ARPA
B.IP6-SERVERS.ARPA
C.IP6-SERVERS.ARPA
D.IP6-SERVERS.ARPA
E.IP6-SERVERS.ARPA
F.IP6-SERVERS.ARPA
...
The IP6-SERVERS.ARPA zone will be delegated to the same set of
servers as IP6.ARPA. IPv4 and IPv6 glue records for each of those
servers will be added to the ARPA zone.
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4. IAB Statement
In its capacity as the body that provides technical guidance to ICANN
for the administration of the ARPA top-level domain as described in
[RFC3172], the IAB has reviewed this proposal and supports it as an
operational change that is in line with the respective roles of ICANN
and the IAB.
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5. IANA Considerations
With due consideration to the approval of the IAB (see Section 4) the
IANA is directed to delegate:
1. IN-ADDR-SERVERS.ARPA to the nameservers listed in Section 2;
2. IP6-SERVERS.ARPA to the nameservers listed in Section 3.
The IANA is further directed to install IPv4 and IPv6 glue records
for the nameservers concerned in the ARPA zone.
The choice of operators for all nameservers concerned is beyond the
scope of this document, and is an IANA function which falls under the
scope of section 4 of the MoU between the IETF and ICANN [RFC2860].
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6. Security Considerations
This document introduces no additional security risks for the
Internet.
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7. References
7.1. Normative References
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, November 1987.
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987.
[RFC3172] Huston, G., "Management Guidelines & Operational
Requirements for the Address and Routing Parameter Area
Domain ("arpa")", BCP 52, RFC 3172, September 2001.
7.2. Informative References
[RFC2860] Carpenter, B., Baker, F., and M. Roberts, "Memorandum of
Understanding Concerning the Technical Work of the
Internet Assigned Numbers Authority", RFC 2860, June 2000.
[RFC3152] Bush, R., "Delegation of IP6.ARPA", BCP 49, RFC 3152,
August 2001.
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Appendix A. Existing NS RRSets
The NS RRSet for the IN-ADDR.ARPA zone at the time of writing is as
follows:
IN-ADDR.ARPA. 86400 IN NS A.ROOT-SERVERS.NET.
IN-ADDR.ARPA. 86400 IN NS B.ROOT-SERVERS.NET.
IN-ADDR.ARPA. 86400 IN NS C.ROOT-SERVERS.NET.
IN-ADDR.ARPA. 86400 IN NS D.ROOT-SERVERS.NET.
IN-ADDR.ARPA. 86400 IN NS E.ROOT-SERVERS.NET.
IN-ADDR.ARPA. 86400 IN NS F.ROOT-SERVERS.NET.
IN-ADDR.ARPA. 86400 IN NS G.ROOT-SERVERS.NET.
IN-ADDR.ARPA. 86400 IN NS H.ROOT-SERVERS.NET.
IN-ADDR.ARPA. 86400 IN NS I.ROOT-SERVERS.NET.
IN-ADDR.ARPA. 86400 IN NS K.ROOT-SERVERS.NET.
IN-ADDR.ARPA. 86400 IN NS L.ROOT-SERVERS.NET.
IN-ADDR.ARPA. 86400 IN NS M.ROOT-SERVERS.NET.
The NS RRSet for the IP6.ARPA zone at the time of writing is as
follows:
IP6.ARPA. 84600 IN NS NS-SEC.RIPE.NET.
IP6.ARPA. 86400 IN NS SEC1.APNIC.NET.
IP6.ARPA. 86400 IN NS NS2.LACNIC.NET.
IP6.ARPA. 86400 IN NS NS.ICANN.ORG.
IP6.ARPA. 86400 IN NS TINNIE.ARIN.NET.
For completeness, the NS RRSet for the ARPA zone at the time of
writing is as follows:
ARPA. 86400 IN NS A.ROOT-SERVERS.NET.
ARPA. 86400 IN NS B.ROOT-SERVERS.NET.
ARPA. 86400 IN NS C.ROOT-SERVERS.NET.
ARPA. 86400 IN NS D.ROOT-SERVERS.NET.
ARPA. 86400 IN NS E.ROOT-SERVERS.NET.
ARPA. 86400 IN NS F.ROOT-SERVERS.NET.
ARPA. 86400 IN NS G.ROOT-SERVERS.NET.
ARPA. 86400 IN NS H.ROOT-SERVERS.NET.
ARPA. 86400 IN NS I.ROOT-SERVERS.NET.
ARPA. 86400 IN NS K.ROOT-SERVERS.NET.
ARPA. 86400 IN NS L.ROOT-SERVERS.NET.
ARPA. 86400 IN NS M.ROOT-SERVERS.NET.
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Appendix B. Performance Characteristics
B.1. Label Compression
The choice of names for the respective NS RRSets of the IN-ADDR.ARPA
and IP6.ARPA zones have a relatively minor impact on the delegation
response sizes from their parent zones given other anticipated
contributors such as DNSSEC. However, it is still considered good
practice to use a naming scheme which is reasonably compressible:
doing so for frequently-queried zones such as these is likely to have
at least measurable impact on aggregate DNS traffic in the Internet
as a whole, and has potential transport benefits to clients whose
queries will not result in secure replies.
The naming schemes described in Section 2 and Section 3 are highly
compressible. That is, once a single nameserver name has been
encoded in a DNS message, subsequent nameservers can be specified
with substantially smaller encoding.
In the DNS, a complete encoding of an a-label involves a one-byte
length field, plus a one-byte-per-character encoding of the a-label
itself. A domain name's encoding consists of one or more a-labels,
so-encoded, plus a single terminating zero byte. Where a terminating
series of a-labels has already been encoded as described above,
subsequent terminating references to the same series can be made
using a two-byte pointer to that full encoding.
The non-compressed representation of the nameserver A.IN-ADDR-
SERVERS.ARPA fills (1 + 1) + (15 + 1) + (4 + 1) + 1 = 24 bytes.
The non-compressed representation of A.IP6-SERVERS.ARPA fills (1 + 1)
+ (10 + 1) + (4 + 1) + 1 = 19 bytes.
Subsequent nameservers under either domain are encoded with the
initial label, plus two bytes for a pointer to the repeated domain
elsewhere in the message. That is, (1 + 1) + 2 = 4 bytes.
The encoded size of the a-labels in a twelve-record NS RRSet named
according to Section 2 for IN-ADDR.ARPA is as follows:
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+------------------------+---------------------------------------+
| Nameserver | Encoded Size |
+------------------------+---------------------------------------+
| A.IN-ADDR-SERVERS.ARPA | (1 + 1) + (15 + 1) + (4 + 1) + 1 = 24 |
| | |
| B.IN-ADDR-SERVERS.ARPA | (1 + 1) + 2 = 4 |
| | |
| C.IN-ADDR-SERVERS.ARPA | (1 + 1) + 2 = 4 |
| | |
| D.IN-ADDR-SERVERS.ARPA | (1 + 1) + 2 = 4 |
| | |
| E.IN-ADDR-SERVERS.ARPA | (1 + 1) + 2 = 4 |
| | |
| F.IN-ADDR-SERVERS.ARPA | (1 + 1) + 2 = 4 |
| | |
| G.IN-ADDR-SERVERS.ARPA | (1 + 1) + 2 = 4 |
| | |
| H.IN-ADDR-SERVERS.ARPA | (1 + 1) + 2 = 4 |
| | |
| I.IN-ADDR-SERVERS.ARPA | (1 + 1) + 2 = 4 |
| | |
| J.IN-ADDR-SERVERS.ARPA | (1 + 1) + 2 = 4 |
| | |
| K.IN-ADDR-SERVERS.ARPA | (1 + 1) + 2 = 4 |
| | |
| L.IN-ADDR-SERVERS.ARPA | (1 + 1) + 2 = 4 |
| | |
| Total | 68 bytes |
+------------------------+---------------------------------------+
The encoded size of the a-labels in a six-record NS RRSet named
according to Section 3 for IP6.ARPA is hence as follows:
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+--------------------+---------------------------------------+
| Nameserver | Encoded Size |
+--------------------+---------------------------------------+
| A.IP6-SERVERS.ARPA | (1 + 1) + (10 + 1) + (4 + 1) + 1 = 19 |
| | |
| B.IP6-SERVERS.ARPA | (1 + 1) + 2 = 4 |
| | |
| C.IP6-SERVERS.ARPA | (1 + 1) + 2 = 4 |
| | |
| D.IP6-SERVERS.ARPA | (1 + 1) + 2 = 4 |
| | |
| E.IP6-SERVERS.ARPA | (1 + 1) + 2 = 4 |
| | |
| F.IP6-SERVERS.ARPA | (1 + 1) + 2 = 4 |
| | |
| Total | 39 bytes |
+--------------------+---------------------------------------+
By way of comparison, the encoded size of the labels in the NS RRSet
for IP6.ARPA shown in Appendix A is as follows:
+-----------------+--------------------------------------+
| Nameserver | Encoded Size |
+-----------------+--------------------------------------+
| NS-SEC.RIPE.NET | (6 + 1) + (4 + 1) + (3 + 1) + 1 = 17 |
| | |
| SEC1.APNIC.NET | (4 + 1) + (5 + 1) + 2 + 1 = 14 |
| | |
| NS2.LANIC.NET | (3 + 1) + (6 + 1) + 2 + 1 = 14 |
| | |
| NS.ICANN.ORG | (2 + 1) + (5 + 1) + (3 + 1) + 1 = 14 |
| | |
| TINNIE.ARIN.NET | (6 + 1) + (4 + 1) + 2 + 1 = 15 |
| | |
| Total | 74 bytes |
+-----------------+--------------------------------------+
B.2. Query Patterns
A brief description of likely query patterns for an empty cache with
the existing and new NS RRSets follow.
B.2.1. QNAME under IN-ADDR.ARPA
Consider the IN-ADDR.ARPA NS RRSet described in Appendix A and a
QNAME which is delegated beneath the IN-ADDR.ARPA zone:
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1. Query sent to root server that is also authoritative for IN-
ADDR.ARPA; response is a referral from the IN-ADDR.ARPA zone.
In the case where the initial query is sent to the J root server:
1. Query sent to J.ROOT-SERVERS.NET (which is not authoritative for
the IN-ADDR.ARPA zone); response is a referral to an ARPA server
with additional-section glue.
2. Query sent to an ARPA server (all of which are also authoritative
in this case for IN-ADDR.ARPA); response is a referral from the
IN-ADDR.ARPA zone.
Consider the same query with the IN-ADDR.ARPA NS RRSet described in
Section 2:
1. Query sent to a root server which is also authoritative for ARPA;
response is a referral to an IN-ADDR.ARPA server, with
additional-section glue.
2. Query sent to an IN-ADDR.ARPA server; response is a referral from
the IN-ADDR.ARPA zone.
In the case where the first query is sent to the J root server:
1. Query sent to J.ROOT-SERVERS.NET (which is not authoritative for
ARPA); response is a referral to an ARPA server, with additional-
section glue.
2. Query sent to an ARPA server; response is a referral to an IN-
ADDR.ARPA server, with additional-section glue.
3. Query sent to an IN-ADDR.ARPA server; response is a referral from
the IN-ADDR.ARPA zone.
B.2.2. QNAME under IP6.ARPA
Consider the IP6.ARPA NS RRSet described in Appendix A and a QNAME
which is delegated beneath the IP6.ARPA zone:
1. Query sent to root server that is also authoritative for ARPA;
response is a referral from the ARPA zone to an IP6.ARPA server
with no additional-section glue.
2. A recursive lookup for one of the nameservers specified in the
referral must now be performed in order to obtain an address for
an IP6.ARPA server. In all cases three queries are required.
Successive recursive lookups may be performed in the event that a
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server is unresponsive.
3. Query sent to IP6.ARPA server; response is a referral from the
IP6.ARPA zone.
In the case where the first query is sent to the J root server:
1. Query sent to J.ROOT-SERVERS.NET; response is a referral to an
ARPA server with additional-section glue.
2. Query sent to an ARPA server; response is a referral from the
ARPA zone to an IP6.ARPA server with no additional-section glue.
3. A recursive lookup for one of the nameservers specified in the
referral must now be performed in order to obtain an address for
an IP6.ARPA server. In all cases three queries are required.
Successive recursive lookups may be performed in the event that a
server is unresponsive.
4. Query sent to IP6.ARPA server; response is a referral from the
IP6.ARPA zone.
Consider the same query with the IP6.ARPA NS RRSet described in
Section 3:
1. Query sent to a root server which is also authoritative for ARPA;
response is a referral to an IP6.ARPA server, with additional-
section glue.
2. Query sent to an IP6.ARPA server; response is a referral from the
IP6.ARPA zone.
In the case where the first query is sent to the J root server:
1. Query sent to J.ROOT-SERVERS.NET (which is not authoritative for
ARPA); response is a referral to an ARPA server, with additional-
section glue.
2. Query sent to an ARPA server; response is a referral to an
IP6.ARPA server with additional-section glue.
3. Query sent to an IP6.ARPA server; response is a referral from the
IP6.ARPA zone.
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Appendix C. Editorial Notes
This section (and sub-sections) to be removed prior to publication.
C.1. Change History
00 Initial draft.
01 Changes made following review by Alfred Hoenes and Danny
McPherson.
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Authors' Addresses
Joe Abley
ICANN
4676 Admiralty Way, Suite 330
Marina del Rey, CA 90292
USA
Phone: +1 310 463 9062
Email: joe.abley@icann.org
Terry Manderson
ICANN
4676 Admiralty Way, Suite 330
Marina del Rey, CA 90292
USA
Phone: +61 4 1127 5673
Email: terry.manderson@icann.org
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