Reverse DNS Naming Convention for CIDR Address Blocks
draft-gersch-dnsop-revdns-cidr-02
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft whose latest revision state is "Expired".
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| Authors | Joe Gersch , Dan Massey , Eric Osterweil | ||
| Last updated | 2012-05-02 | ||
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draft-gersch-dnsop-revdns-cidr-02
Network Working Group J. Gersch
Internet-Draft Secure64 SW Corp
Intended status: Informational D. Massey
Expires: November 2, 2012 Colorado State University
E. Osterweil
Verisign
May 1, 2012
Reverse DNS Naming Convention for CIDR Address Blocks
draft-gersch-dnsop-revdns-cidr-02.txt
Abstract
The reverse DNS naming method is used to specify a complete IP
address. At present there is no standard way for the reverse DNS to
handle address ranges. As an example, there is no formal mechanism
to define a reverse DNS name for the block of addresses specified by
the IPv4 prefix 129.82.0.0/16. Defining such a reverse DNS naming
convention would be useful for a number of applications. This draft
proposes a naming convention for encoding CIDR address blocks into
the reverse DNS namespace.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on November 2, 2012.
Copyright Notice
Copyright (c) 2012 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
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publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Aligning the DNS and IP Hierarchies . . . . . . . . . . . 3
1.2. Purpose . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. Conventions Used In This Document . . . . . . . . . . . . . . 5
3. Design Requirements . . . . . . . . . . . . . . . . . . . . . 6
4. Related Work . . . . . . . . . . . . . . . . . . . . . . . . . 7
4.1. Naming via RFC 1101 . . . . . . . . . . . . . . . . . . . 7
4.2. CIDR Naming via RFC 2317 . . . . . . . . . . . . . . . . . 7
4.3. Prior Work on CIDR Names for Routing . . . . . . . . . . . 8
5. Reverse DNS CIDR Name Specification . . . . . . . . . . . . . 9
5.1. IPv4 Address Block Naming . . . . . . . . . . . . . . . . 9
5.2. IPv6 Address Block Naming . . . . . . . . . . . . . . . . 11
6. Additional Considerations . . . . . . . . . . . . . . . . . . 12
6.1. Legacy Behavior at Octet Boundaries . . . . . . . . . . . 12
6.2. The Naming Convention and Zone Structures . . . . . . . . 13
6.3. Separation of Prefix Data and PTR Records . . . . . . . . 14
6.4. Prefix Enumeration . . . . . . . . . . . . . . . . . . . . 14
6.5. Finding Longest Matches . . . . . . . . . . . . . . . . . 15
7. Security Considerations . . . . . . . . . . . . . . . . . . . 16
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 18
10. Change History . . . . . . . . . . . . . . . . . . . . . . . . 19
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20
11.1. Normative References . . . . . . . . . . . . . . . . . . . 20
11.2. Informative References . . . . . . . . . . . . . . . . . . 20
Appendix A. Example Zone Files . . . . . . . . . . . . . . . . . 21
A.1. Example 1 . . . . . . . . . . . . . . . . . . . . . . . . 21
A.2. Example 2 . . . . . . . . . . . . . . . . . . . . . . . . 22
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 24
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1. Introduction
This draft proposes a common naming convention for entering CIDR
prefixes into the Reverse DNS.
The Reverse DNS provides a naming convention for both IPv4 and IPv6
addresses. At this time, the most common use of the reverse-DNS is
to associate an IP address with a PTR resource record that identifies
the corresponding host name. For example, IP address 129.82.138.2 is
encoded as 2.138.82.129.in-addr.arpa and a PTR resource record
identifies the host name as alpha.netsec.colostate.edu. The Reverse
DNS would be more expressive if we had a formal convention for
encoding and returning information associated with a network address
range, not just a unique IP address. For example, one would like to
store and resolve resource records associated with a prefix range
such as 129.82.128/17.
Given such a capability, a variety of new applications and services
would be enabled. For example, one might store geographic locations
associated with a prefix, prefix ownership information, and a variety
of other data. This list of possible applications is not intended to
be complete, but instead suggest some of the possibilities. This
draft proposes a naming convention for the prefix name and argues
that a process for naming a prefix should be consistent across
applications.
1.1. Aligning the DNS and IP Hierarchies
A key observation is that both the DNS names and IP addresses are
part of a hierarchical tree structure and any naming convention
should respect and align with these tree structures.
In the DNS hierarchical tree structure 128.82.129.in-addr.apra is
logically below 82.129.in-addr.apra, which is logically below 129.in-
addr.arpa. Other "flat" approaches to naming, such as Distributed
Hash Tables, have been proposed, but the DNS tree structure remains a
powerful abstraction. It forms the basis for the operation of DNS;
caching, delegation, DNSSEC signing, and so forth all benefit from
the DNS tree structure.
IP addresses also have a logical tree structure where 129.82.128.0/24
is subprefix (logically below) 129.82.0.0/16 which is a subprefix of
129.0.0.0/8. The reverse DNS aligns with the structure;
128.82.129.in-addr.arpa is logically below 82.129.in-addr.arpa which
is logically below 129.in-addr.arpa. This alignment between the DNS
hierarchy and the IP address hierarchy serves both systems well and
allows one to easily encode prefixes that fall on an octet boundary
(e.g. IPv4 prefixes whose mask length is a multiple of 8).
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The challenge is to preserve this alignment even when even when CIDR
prefixes do not fall on octet boundaries. For example,
129.82.128.0/19 is a subprefix of 129.82.128.0/18. The DNS name for
129.82.128.0/19 should be logically below the DNS name for
129.82.128.0/18. This document introduces a naming convention for
CIDR prefixes that preserves this alignment.
1.2. Purpose
In order to enable these applications, one must map an IPv4 or IPv6
prefix into a reverse-DNS name. There are various subtleties,
advantages and disadvantages that emerge when trying to define a
naming convention. Today, zone administrators can use their own
individual approaches to encode a prefix in the reverse DNS. This
requires no DNS protocol changes and no modifications to resolvers,
caches, or authoritative servers. The emergence of different
encoding standards complicates (but does not prevent) the design of
systems that would make use of these resource records. The aim of
this work is to introduce a standard convention.
1.3. Terminology
The following terms are used throughout out the document:
Reverse DNS:
We use the term Reverse DNS to refer to the domains in-addr.arpa
and ip6.arpa.
Prefix:
A prefix refers to IPv4 or IPv6 address range specified by a
network portion and mask length, as described in [RFC4632]. For
example, 129.82.0.0/16 and 129.82.128/18 are examples of IPv4
prefixes.
Octet Boundary:
An IPv4 prefix falls on an octet boundary if its mask length is a
multiple 8. For example, 129.82.0.0/16 is on an octet boundary
while 129.82.128/18 does not fall on octet boundary. Prefixes
that are on octet boundary naturally map to the reverse DNS.
Prefixes that are not on octet boundary are more complex and the
main challenge for any naming convention.
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2. Conventions Used In This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
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3. Design Requirements
A naming convention to specify CIDR address blocks in the reverse-DNS
has several design goals:
1. Autonomy: The owner of a reverse-DNS zone file associated with a
CIDR address block should be able to act independently from any
other organization in order to create or modify data records
within the DNS zone.
2. Coverage Authority: With the exception of data that has been sub-
delegated to a child zone, the reverse DNS zone must be
authoritative for all sub-prefixes below the covering prefix.
Any query for a sub-prefix must be answered with a data record or
NXDOMAIN specifying this zone as the authority.
3. Allow Delegation: It must allow the zone owner to delegate
smaller address blocks to a child zone which will be
independently managed.
4. Conformance: It should align with naming conventions and
delegation structures already in use by the RIR's for IN-
ADDR.ARPA and IP6.ARPA.
5. Simplicity: The naming structure should be understandable, or at
a minimum, able to be easily constructed by software provisioning
tools and utilities such as DIG.
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4. Related Work
The process of mapping CIDR addresses into the reverse-DNS name space
is difficult because the prefix length of an IPv4 CIDR address is an
arbitrary number from 0 to 32. These numbers do not necessarily
align with an IPv4 octet.
4.1. Naming via RFC 1101
The problem of associating records with network names dates back to
at least [RFC1101]. This work coincides with some of the early
development of DNS and discusses issues regarding hosts.txt files.
The RFC observation makes a key observation that one should provide
"mappings for subnets, even when nested".
The approach taken here clearly states how to map an IPv4 prefix that
is on an octet boundary. The RFC maps "10.IN-ADDR.ARPA for class A
net 10, 2.128.IN-ADDR.ARPA for class B net 128.2, etc." This is
essentially the same as the approach proposed here, although we
append an "m" label (discussed later in this document).
[RFC1101] also mentions more specific subnets, but the details are
limited. We believe the approach proposed here builds on the best
ideas from this RFC and expands on the details of how the naming
convention would work.
4.2. CIDR Naming via RFC 2317
Since CIDR address no longer align with octet boundaries, the CIDR
specification in [RFC4632] notes that there is "some increase in work
for those who maintain parts of the IN-ADDR.ARPA zone." [RFC2317] is
offered as a technique to populate IN-ADDR.ARPA. The intent of this
work is to encode IPv4 addresses and the approach is designed to
"address spaces covering fewer than 256 addresses."
Suppose organization A owns 129.82.138.0/30. This address space
covers four IPv4 addresses; namely 129.82.138.0, 129.82.138.1,
129.82.138.2 and 129.82.138.3. Giving organization A control of the
reverse zone "138.82.129.in-addr.arpa." would allow Organization A to
enter PTR resource records for each of its 4 addresses. However, it
also gives organization A the ability to enter PTR resource records
for 252 other IP addresses from 129.82.138.4 to 129.82.138.255.
These addresses are managed by other organizations. Sharing the
138.82.129.in-addr.arpa between multiple organization is not
practical and creating a separate zone for each IP address (e.g.
creating the zone 0.138.82.129.in-addr.arpa) is very high overhead to
store a single PTR record.
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[RFC2317] addresses this problem by creating CNAME records in
138.82.129.in-addr.arpa zone. Organization A administers a zone
named 0/32.138.129.in-addr.arpa. CNAME records in the 138.82.129.in-
addr.arpa zone point to entries in Organization A's
0/32.138.82.129.in-addr.arpa zone. For example, 1.138.82.129.in-
addr.arpa. is a CNAME pointing to 1.0/32.138.82.129.in-addr.arpa. A
full description is found in [RFC2317].
This approach was not intended to encode IP address for address
spaces smaller than a "/24". It was not intended for encoding
prefixes. It does not specify how one might encode a prefix and it
is not trivial to extend this approach to CIDR prefixes. In
particular, the design requirements of Coverage Authority, Allowing
Delegation, and arguably Simplicity are not easily met by extending
the RFC to included prefixes.
4.3. Prior Work on CIDR Names for Routing
Over a decade ago, [I-D.bates-bgp4-nlri-orig-verif] proposed to use
the reverse DNS to verify the origin AS associated with a prefix.
This requires both a naming convention for converting the name into a
prefix and additional resource record types for storing origin
information, along with recommendations on their use.
Our focus in this draft is on the naming convention. Draft
[I-D.bates-bgp4-nlri-orig-verif] as well as other subsequent work on
BGP security, extends [RFC2317] style names to encode a prefix. For
example, the draft proposes to encode the prefix 10.1.128/20 as the
DNS name 128/20.1.10.bgp.in-addr.arpa.
In [I-D.bates-bgp4-nlri-orig-verif], the DNS hierarchy and the IP
address hierarchy diverge and the approach fails to meet the Coverage
Authority requirement. To see this, consider the prefixes
10.1.128/20 and 10.1.128/21. in CIDR terminology, 10.1.128/21 is
covered by 10.1.128/20, but this relationship is not captured in the
DNS hierarchy. 10.1.128/21 is encoded as 128/21.1.10.bgp.in-addr.arpa
and thus 10.1.128/20 and 10.1.128/21 are siblings in the DNS tree
structure.
This can be overcome by introducing a large number of CNAME records;
one for every potential subprefix. We instead provide an approach
where the CIDR hierarchy and DNS hierarchy align.
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5. Reverse DNS CIDR Name Specification
The naming method described in this section is based on the well-
known technique of ANDing a bit-mask with the low-order octet of an
IP address. The binary result is then broken up into individual sub-
names using the "." separator. The result looks like an ENUM or IPv6
reverse-DNS address; that is, a string of chained empty non-terminal
sub-names.
This name-chaining creates the desired effect of being able to allow
a DNS zone delegation at any point in the chain. The naming scheme
allows the creation of two /17's from a /16, two /18's from a /17,
and so on.
5.1. IPv4 Address Block Naming
The CIDR to Reverse-DNS naming convention works as follows:
1. Remove any octets that are not significant. An octet is
significant if it includes any part of the network address. An
octet is not significant if all bits correspond to the host
portion of the address. For example, 129.82.0.0/16 --> 129.82
and 129.82.160.0/19 --> 129.82.160
2. Calculate N where N = prefix_length mod 8. If N equals 0, invert
the address and insert a "m" label as the first label to indicate
this a prefix name and append in-addr.arpa to the end, per the
usual reverse-DNS method; 129.82 --> m.82.129.in-addr.arpa.
3. If N is not equal 0, the prefix is not on an octet boundary and
we perform the following name construction:
A. Truncate the name to remove the least significant octet. Add
a "m" label to this domain name to indicate "mask".
B. Convert the least significant octet to binary, separating
each bit into its own label (with a "." character).
C. Truncate the binary labels to the N significant labels that
correspond to the given prefix_length.
D. Reverse the string and add ".in-addr.arpa."
Several examples illustrate this algorithm. These examples show the
conversion to binary, followed by the truncation, followed by the
name reversal.
129.82.0.0/16 --> m.82.129.in-addr.arpa. (at octet boundary)
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129.82.64.0/18 --> 129.82.m.0.1.0.0.0.0.0.0
--> 129.82.m.0.1 (N = 18 mod 8 = 2)
--> 1.0.m.82.129.in-addr.arpa.
129.82.64.0/20 --> 129.82.m.0.1.0.0.0.0.0.0
--> 129.82.m.0.1.0.0 (N = 20 mod 8 = 4)
--> 0.0.1.0.m.82.129.in-addr.arpa.
129.82.160.0/20 --> 129.82.m.1.0.1.0.0.0.0.0
--> 129.82.m.1.0.1.0 (N = 20 mod 8 = 4)
--> 0.1.0.1.m.82.129.in-addr.arpa.
129.82.160.0/23 --> 129.82.m.1.0.1.0.0.0.0.0
--> 129.82.m.1.0.1.0.0.0.0 (N = 23 mod 8 = 7)
--> 0.0.0.0.1.0.1.m.82.129.in-addr.arpa.
15.192.0.0/12 --> 15.192.m.1.1.0.0.0.0.0.0
--> 15.192.m.1.1.0.0 (N = 12 mod 8 = 4)
--> 0.0.1.1.m.15.in-addr.arpa.
The conversion from a reverse-DNS name back to CIDR is simple. First
calculate the prefix length from the name using the formula:
plen = 8*(count of full octets) + (count of binary digits)
Then reverse the string, add up the values of the binary digits to
build a final octet, then append a "/" and the prefix length.
Examples:
1.0.m.82.129.in-addr.arpa --> 129.82.64.0/18
(example has 2 octets + 2 binary digits, so mask length = 18)
0.0.1.0.m.82.129.in-addr.arpa --> 129.82.64.0/20
(example has 2 octets + 4 binary digits, so mask length = 20)
0.0.0.1.0.1.m.129.in-addr.arpa--> 129.160.0/14
(example has 1 octet + 6 binary digits, so mask length = 14)
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5.2. IPv6 Address Block Naming
The IPv6 naming convention is similar, with the exception that 4-bit
nibble boundaries are used instead of octets, the mod calculation is
based on 4 instead of 8, and "ip6.arpa" is used as the suffix.
Examples:
2607:fa88::/32 --> m.8.8.a.f.7.0.6.2.ip6.arpa
(on nibble boundary)
2607:fa88:8000::/33 --> 2.6.0.7.f.a.8.8.m.1.0.0.0
--> 2.6.0.7.d.a.8.8.m.1 (33 mod 4 = 1)
--> 1.m.8.8.a.f.7.0.6.2.ip6.arpa
2607:fa88:e000::/35 --> 2.6.0.7.f.a.8.8.m.1.1.1.0
--> 2.6.0.7.d.a.8.8.m.1.1.1(35 mod 4 = 3)
--> 1.1.1.m.8.8.a.f.7.0.6.2.ip6.arpa
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6. Additional Considerations
This draft proposes a naming convention for IPv4 and IPv6 prefixes.
With the introduction of a such a convention, a number of new
possibilities are enabled and a number of issues have been raised.
In this section, we summarize some of the main discussions. Though
these are not directly part of the naming convention, they do help to
review issues that may help application designers make better use of
prefix names and help operators manage reverse zones. We first
discuss how the naming convention interacts with the current octet
(IPv4) or nibble (IPv6) based reverse DNS tree structure and then
turn to the problem of prefix enumeration and find the longest match
for a prefix.
6.1. Legacy Behavior at Octet Boundaries
The existing reverse DNS structure is aligned on octet boundaries for
IPv4 and nibble boundaries for IPv6. The naming convention
introduced here adds to the existing reverse DNS tree; it does not
change the existing structure. This is a deliberate choice not to
reinvent the reverse DNS but rather to enhance the existing
structure. The naming convention proposed here builds on the
existing reverse DNS structure and thus inherits both advantages and
disadvantages from the existing system.
One disadvantage is the existing octet boundary based tree for IPv4
(and nibble based tree for IPv6). To understand why this is a
disadvantage, suppose organization A owns the address space
129.82.0.0/16. Organization A allocates the address space
129.82.128.0/17 to Organization B. In typical operations,
Organization A would delegate 128 zones to Organization B; the zones
128.82.129.in-addr.arpa, 129.82.129.in-addr.arpa, ..., 255.82.129.in-
addr.arpa. Because the reverse DNS had no notion of CIDR prefixes,
all 128 delegations are need to give organization B full control over
its PTR records.
The example becomes worse if Organization B further suballocates
129.82.128/22 to Organization C. In this case, Organization C needs
to be given operational control of 4 zones; 128.82.129.in-addr.arpa,
129.82.129.in-addr.arpa. 130.82.129.in-addr.arpa, and 131.82.129.in-
addr.arpa. Delegating these zones to organization C requires an
action by the owner of 82.129.in-addr.arpa. Note that Organization
does not have a business relationship with Organization A.
Organization C needs to pass information to Organization B who in
turn needs to pass the information to Organization A.
The above operation is not ideal. Delegating a non-octet boundary
prefix requires the delegation of multiple zones. Subdelegation can
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require communication with organizations that do not have direct
business relationships. But it is essential to note that this is how
the reverse DNS currently operates and has successfully operated for
many years. Operational techniques have been developed to manage PTR
records and their respective zones. For better or worse, these
practices continue to work with this naming convention.
The naming convention here does introduce additional names for
prefixes. In the example above, Organization A could delegate the
1.m.82.129.in-addr.apra to Organization B. Organization B could in
turn delegate 0.0.0.0.0.1.m.82.129.in-addr.arpa to Organization C.
Note the naming convention has allowed delegation of prefixes to work
in an efficient manner that respects business relationships. For
example, Organization B can delegate the prefix 129.82.128/22 to
Organization C without ever involving Organization A. Had this naming
convention been in place for the original reverse DNS, much of the
suboptimal behavior discussed above could have been avoided.
However, the naming convention explicitly chooses to enhance the
existing reverse DNS tree rather than replace.
We note that the naming convention uses the letter "m" to indicate a
transition from octet/nibble numbering to binary numbering for the
remainder of the name. Nothing restricts a DNS administrator from
creating a name in which the sequence of binary digits extends past
the next octet or nibble boundary. Applications may actually find
this to be a useful capability. Nevertheless, this document defines
a naming convention where each prefix maps to a unique name, as
described in section 5. We therefore add the restriction that any
application looking for records associated with a prefix MUST check
standard naming convention (e.g. m.0.82.129.in-addr.arpa at an octet
boundary) and if the desired records are found, the application MUST
prefer these records over any records found at a non-standard
encoding.
6.2. The Naming Convention and Zone Structures
The naming convention does not impose any semantics on zone
structure. As with any DNS name, a resolver need not be aware of how
the zone cuts are structured and no specific requirements are added
for zone management. For example, some sites may choose to delegate
at a subprefix boundary while others maintain one large zone. Names
can make use of CNAME and DNAME records if the zone administrator so
desires. This is simply a naming convention and does not change any
existing resolver or server behavior.
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6.3. Separation of Prefix Data and PTR Records
Some organization may want to separate the administration of prefix
related data (geolocations, prefix ownership, and so forth) from the
management of traditional PTR records. Note that all prefix related
data is stored at a name that includes the "m" label. This "m" label
could be used as delegation point to separate the administration of
prefix data from the administration of PTR records.
To illustrate this, suppose the owner of 129.82.128/17 would like one
to keep the management of prefix related data distinct from the
management of their PTR records. Note that for all prefixes with a
mask length between 17 and 23 are part of the zone 1.m.82.129.in-
addr.arpa. This zone can simply be delegated to the group managing
prefix related data while the group managing PTR records continues to
be responsible for the zones 128.82.129.in-addr.arpa to
255.82.129.in-addr.arpa.
If prefix data is also to be stored at mask lengths ranging between
24 and 32, then m.128.82.129.in-addr.arpa to m.255.82.129.in-
addr.arpa can also be delegated to the group managing prefix data.
In this sense, an organization can keep a complete separation between
groups managing prefix data and groups managing PTR records.
During the discussion of the draft, some organizations expressed a
desire to achieve this type of separation in operational practice.
In particular, groups associated with routing and prefix management
might manage the prefix related records while other groups associated
with DHCP and IP address management currently manage the PTR records.
This example simply illustrates these groups can be kept distinct if
an organization so desires. As with any DNS deployment, an
organization makes its own decisions on where to make zone cuts and
how to manage their own delegation.
6.4. Prefix Enumeration
This document introduces a convention for naming IPv4 and IPv6
prefixes. It is not an enumeration technique. To illustrate the
difference between lookup and enumeration we consider a hypothetical
application that uses LOC resource records to associate geographic
locations with prefixes. Note the use of the LOC record is simply to
make the example concrete and the same argument applies to any type
of data stored at a prefix.
An application can easily lookup the LOC resource record associated
with a prefix using this naming convention. The application simply
converts the prefix (IPv4 or IPv6) into a DNS name as described in
the previous sections and queries for the LOC record associated with
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that name. Using DNSSEC, an application can also authenticate the
LOC record or provide authenticated denial of existence proving that
no such LOC record exists.
A distinct question is how one might enumerate all possible prefixes
that have LOC records. The naming convention does not directly
provide enumeration. Applications might develop strategies for
searching all possible names by variations of brute force searches,
exploiting NSEC records (if used), or by adding additional record
types to aid in finding related prefixes. The naming convention
proposed here does not provide an explicit mechanism to enumerate all
prefixes with a particular resource record type.
6.5. Finding Longest Matches
Another distinct question is how one could find the longest match for
a given IP address or prefix. For example, the application might
want to find the most specific prefix (longest match) that has a LOC
record and covers a particular IP address. Similar to enumeration,
the naming convention does not directly provide longest match.
Applications might develop strategies for searching all covering
prefixes using variations of brute force searches, exploiting NSEC
records (if used), using NXDOMAIN queries to find zone boundaries, or
by adding additional record types to aid in finding related prefixes.
These techniques are application-dependent. The naming convention
proposed here does not provide an explicit mechanism to find the
longest matching prefix for an IP address.
The naming convention proposed here provides a way to name a prefix.
Once one has this name, all the advantages (and disadvantages) of DNS
apply. One can easily issue queries for the name and retrieve
resource records associated with that name. For many applications,
this is sufficient. Applications that require more complex prefix
related functions, such as enumerating all prefixes of a given type
or finding the longest prefix match, need to build this functionality
into their application. The naming convention provides the necessary
building blocks to achieve this, but does not dictate how a
particular application will assemble the building blocks.
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7. Security Considerations
This document only introduces a naming convention. Applications that
make use of this naming convention may require the use of DNSSEC to
validate the resource records stored at these names.
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8. IANA Considerations
This document does not request any IANA action.
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9. Acknowledgments
The authors would like to thank Danny McPherson (Verisign), Lixia
Zhang (UCLA), and Kim Claffy (CAIDA) for their comments and
suggestions. This document was aided via numerous discussions at
NANOG, IETF and private meetings with ISPs, telecomm carriers, and
research organizations too numerous to mention by name. Thanks to
all for your comments and advice.
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10. Change History
Changes from version 01 to 02
Concerns were raised at the IETF 83 meeting that the document
appeared to specific to the routing application. Several other
applications were mentioned. We clarified the introduction to
show that the naming convention is application agnostic.
Expanded the related work discussion to include RFC 1101.
The "m" label is now added even when on an octet boundary.
Moved all other discussion into the Additional Considerations
section; removing the alternate naming and replacing it with a
discussion of existing delegations, adding a section on separating
prefix and PTR records, added a section on enumerating prefixes
and finding longest matches. All these changes reflect comments
from the mailing list, IETF 83 discussions, and other comments.
They do not change the naming scheme itself.
To emphasize the approach is application agnostic, the appendix
examples were changed from using routing security records to LOC
records. Any record type could be used, but LOC records were
chosen as they were viewed as easy to understand.
Changes from version 00 to 01
Introduction added an additional subsection on aligning the DNS
hierarchy with the IP address hierarchy.
Clarified step 1 of the naming algorithm on removing octets that
are not significant.
Expanded and clarified the discussion of alternate name encoding
for prefixes on an octet boundary.
Added Eric Osterweil as a co-author
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11. References
11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4632] Fuller, V. and T. Li, "Classless Inter-domain Routing
(CIDR): The Internet Address Assignment and Aggregation
Plan", BCP 122, RFC 4632, August 2006.
11.2. Informative References
[I-D.bates-bgp4-nlri-orig-verif]
Bates, T., Bush, R., Li, T., and Y. Rekhter, "DNS-based
NLRI origin AS verification in BGP",
draft-bates-bgp4-nlri-orig-verif-00 (work in progress),
January 1998.
[I-D.gersch-grow-revdns-bgp]
Gersch, J., Massey, D., Osterweil, E., and L. Zhang, "DNS
Resource Records for BGP Routing Data",
draft-gersch-grow-revdns-bgp-00 (work in progress),
February 2012.
[I-D.howard-isp-ip6rdns]
Howard, L. and A. Durand, "Reverse DNS in IPv6 for
Internet Service Providers", draft-howard-isp-ip6rdns-04
(work in progress), September 2010.
[RFC1101] Mockapetris, P., "DNS encoding of network names and other
types", RFC 1101, April 1989.
[RFC2317] Eidnes, H., de Groot, G., and P. Vixie, "Classless IN-
ADDR.ARPA delegation", BCP 20, RFC 2317, March 1998.
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Appendix A. Example Zone Files
A.1. Example 1
This example shows several DNS records added to an existing reverse-
DNS zone file at octet boundary 129.82.0.0/16. The records show how
LOC records could be specified in the zone file to be associated with
an address block. Otherwise no other changes were made. This
example has added records with LOC information pertinent to address
blocks 129.82/16 and the four /18's at 129.82.0.0/18, 129.82.64.0/18,
129.82.128.0/18, and 129.82.192.0/18.
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$TTL 3600
$ORIGIN 82.129.in-addr.arpa.
@ IN SOA rush.colostate.edu. dnsadmin.colostate.edu. (
2012021300 ; serial number
900 ; refresh, 15 minutes
600 ; update retry, 10 minutes
86400 ; expiry, 1 day
3600 ; minimum, 1 hour
)
IN NS dns1.colostate.edu.
IN NS dns2.colostate.edu.
m IN LOC latitude/longitude info for the /16
; 129.82.0.0/16
0.0.m IN LOC lat/long for North campus
; 129.82.0.0/18
1.0.m IN LOC lat/long for South campus
; 129.82.64.0/18
0.1.m IN LOC lat/long for Denver campus
; 129.82.128.0/18
1.1.m IN LOC lat/long for Boulder campus
; 129.82.192.0/18
; delegations required for 256 /24 zones which contain PTR records
1 IN NS dns1.colostate.edu.
IN NS dns2.colostate.edu.
2 IN NS dns1.colostate.edu.
IN NS dns2.colostate.edu.
; continuation to 255 is left out for the sake of brevity
A.2. Example 2
This example illustrates the creation of a new zone for
216.17.128.0/17 which is not at an octet boundary. The existing 256
zones delegated at IN-ADDR.ARPA for the range 0.17.128 through
255.17.216.in-addr.arpa remain unchanged; they contain PTR records
maintained by the appropriate zone owners.
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In this example we have added several records all at the same domain
name with information pertinent to address block 216.17.128.0/17.
Only a single new delegation needs to be added to IN-ADDR.ARPA:
1.m.17.216.in-addr.arpa NS ns.frii.net
This delegation refers to the new /17 zone and is not in conflict
with any of the pre-existing /24 zones.
$TTL 3600
$ORIGIN 1.m.17.216.in-addr.arpa.
@ IN SOA ns1.frii.net. hostmaster.frii.net. (
2012021300 ; serial number
14400 ; refresh, 4 hours
3600 ; update retry, 1 hour
604800 ; expiry, 7 days
600 ; minimum, 10 minutes
)
IN NS ns1.frii.net.
IN NS ns2.frii.net.
$ORIGIN 17.216.in-addr.arpa.
1.m LOC lat/long for main office
;216.17.128.0/17
; no other delegations or PTR records are needed in this zone file
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Authors' Addresses
Joe Gersch
Secure64 SW Corp
Fort Collins, CO
US
Email: joe.gersch@secure64.com
Dan Massey
Colorado State University
Fort Collins, CO
US
Email: massey@cs.colostate.edu
Eric Osterweil
Verisign
Reston, VA
US
Email: eosterweil@verisign.com
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