Network Working Group M. Daniele
Request for Comments: 4001 SyAM Software, Inc.
Obsoletes: 3291 B. Haberman
Category: Standards Track Johns Hopkins University
S. Routhier
Wind River Systems, Inc.
J. Schoenwaelder
International University Bremen
February 2005
Textual Conventions for Internet Network Addresses
Status of This Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
This MIB module defines textual conventions to represent commonly
used Internet network layer addressing information. The intent is
that these textual conventions will be imported and used in MIB
modules that would otherwise define their own representations.
Daniele, et al. Standards Track [Page 1]
RFC 4001 Internet Network Address Conventions February 2005
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. The Internet-Standard Management Framework . . . . . . . . . . 4
3. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Usage Hints . . . . . . . . . . . . . . . . . . . . . . . . . 13
4.1. Table Indexing . . . . . . . . . . . . . . . . . . . . . 14
4.2. Uniqueness of Addresses . . . . . . . . . . . . . . . . 14
4.3. Multiple Addresses per Host . . . . . . . . . . . . . . 15
4.4. Resolving DNS Names . . . . . . . . . . . . . . . . . . 15
5. Table Indexing Example . . . . . . . . . . . . . . . . . . . . 15
6. Security Considerations . . . . . . . . . . . . . . . . . . . 17
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 18
8. Changes from RFC 3291 to RFC 4001 . . . . . . . . . . . . . . 18
9. Changes from RFC 2851 to RFC 3291 . . . . . . . . . . . . . . 18
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 19
10.1. Normative References . . . . . . . . . . . . . . . . . . 19
10.2. Informative References . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 21
Full Copyright Statement . . . . . . . . . . . . . . . . . . . . . 22
1. Introduction
Several standards-track MIB modules use the IpAddress SMIv2 base
type. This limits the applicability of these MIB modules to IP
Version 4 (IPv4), as the IpAddress SMIv2 base type can only contain
4-byte IPv4 addresses. The IpAddress SMIv2 base type has become
problematic with the introduction of IP Version 6 (IPv6) addresses
[RFC3513].
This document defines multiple textual conventions (TCs) as a means
to express generic Internet network layer addresses within MIB module
specifications. The solution is compatible with SMIv2 (STD 58) and
SMIv1 (STD 16). New MIB definitions that have to express network
layer Internet addresses SHOULD use the textual conventions defined
in this memo. New MIB modules SHOULD NOT use the SMIv2 IpAddress
base type anymore.
A generic Internet address consists of two objects: one whose syntax
is InetAddressType, and another whose syntax is InetAddress. The
value of the first object determines how the value of the second is
encoded. The InetAddress textual convention represents an opaque
Internet address value. The InetAddressType enumeration is used to
"cast" the InetAddress value into a concrete textual convention for
the address type. This usage of multiple textual conventions allows
expression of the display characteristics of each address type and
makes the set of defined Internet address types extensible.
Daniele, et al. Standards Track [Page 2]
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The textual conventions for well-known transport domains support
scoped Internet addresses. The scope of an Internet address is a
topological span within which the address may be used as a unique
identifier for an interface or set of interfaces. A scope zone (or,
simply, a zone) is a concrete connected region of topology of a given
scope. Note that a zone is a particular instance of a topological
region, whereas a scope is the size of a topological region
[RFC4007]. Since Internet addresses on devices that connect multiple
zones are not necessarily unique, an additional zone index is needed
on these devices to select an interface. The textual conventions
InetAddressIPv4z and InetAddressIPv6z are provided to support
Internet addresses that include a zone index. To support arbitrary
combinations of scoped Internet addresses, MIB authors SHOULD use a
separate InetAddressType object for each InetAddress object.
The textual conventions defined in this document can also be used to
represent generic Internet subnets and Internet address ranges. A
generic Internet subnet is represented by three objects: one whose
syntax is InetAddressType, a second one whose syntax is InetAddress,
and a third one whose syntax is InetAddressPrefixLength. The
InetAddressType value again determines the concrete format of the
InetAddress value, whereas the InetAddressPrefixLength identifies the
Internet network address prefix.
A generic range of consecutive Internet addresses is represented by
three objects. The first one has the syntax InetAddressType, and the
remaining objects have the syntax InetAddress and specify the start
and end of the address range. Again, the InetAddressType value
determines the format of the InetAddress values.
The textual conventions defined in this document can be used to
define Internet addresses by using DNS domain names in addition to
IPv4 and IPv6 addresses. A MIB designer can write compliance
statements to express that only a subset of the possible address
types must be supported by a compliant implementation.
MIB developers who need to represent Internet addresses SHOULD use
these definitions whenever applicable, as opposed to defining their
own constructs. Even MIB modules that only need to represent IPv4 or
IPv6 addresses SHOULD use the InetAddressType/InetAddress textual
conventions defined in this memo.
There are many widely deployed MIB modules that use IPv4 addresses
and that have to be revised to support IPv6. These MIB modules can
be categorized as follows:
Daniele, et al. Standards Track [Page 3]
RFC 4001 Internet Network Address Conventions February 2005
1. MIB modules that define management information that is, in
principle, IP version neutral, but the MIB currently uses
addressing constructs specific to a certain IP version.
2. MIB modules that define management information that is specific
to a particular IP version (either IPv4 or IPv6) and that is very
unlikely to ever be applicable to another IP version.
MIB modules of the first type SHOULD provide object definitions
(e.g., tables) that work with all versions of IP. In particular,
when revising a MIB module that contains IPv4 specific tables, it is
suggested to define new tables using the textual conventions defined
in this memo that support all versions of IP. The status of the new
tables SHOULD be "current", whereas the status of the old IP version
specific tables SHOULD be changed to "deprecated". The other
approach, of having multiple similar tables for different IP
versions, is strongly discouraged.
MIB modules of the second type, which are inherently IP version
specific, do not need to be redefined. Note that even in this case,
any additions to these MIB modules or to new IP version specific MIB
modules SHOULD use the textual conventions defined in this memo.
MIB developers SHOULD NOT use the textual conventions defined in this
document to represent generic transport layer addresses. A special
set of textual conventions for this purpose is defined in RFC 3419
[RFC3419].
The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY",
in this document are to be interpreted as described in RFC 2119
[RFC2119].
2. The Internet-Standard Management Framework
For a detailed overview of the documents that describe the current
Internet-Standard Management Framework, please refer to section 7 of
RFC 3410 [RFC3410].
Managed objects are accessed via a virtual information store, termed
the Management Information Base or MIB. MIB objects are generally
accessed through the Simple Network Management Protocol (SNMP).
Objects in the MIB are defined using the mechanisms defined in the
Structure of Management Information (SMI). This memo specifies a MIB
module that is compliant to the SMIv2, which is described in STD 58,
RFC 2578 [RFC2578], STD 58, RFC 2579 [RFC2579] and STD 58, RFC 2580
[RFC2580].
Daniele, et al. Standards Track [Page 4]
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3. Definitions
INET-ADDRESS-MIB DEFINITIONS ::= BEGIN
IMPORTS
MODULE-IDENTITY, mib-2, Unsigned32 FROM SNMPv2-SMI
TEXTUAL-CONVENTION FROM SNMPv2-TC;
inetAddressMIB MODULE-IDENTITY
LAST-UPDATED "200502040000Z"
ORGANIZATION
"IETF Operations and Management Area"
CONTACT-INFO
"Juergen Schoenwaelder (Editor)
International University Bremen
P.O. Box 750 561
28725 Bremen, Germany
Phone: +49 421 200-3587
EMail: j.schoenwaelder@iu-bremen.de
Send comments to ."
DESCRIPTION
"This MIB module defines textual conventions for
representing Internet addresses. An Internet
address can be an IPv4 address, an IPv6 address,
or a DNS domain name. This module also defines
textual conventions for Internet port numbers,
autonomous system numbers, and the length of an
Internet address prefix.
Copyright (C) The Internet Society (2005). This version
of this MIB module is part of RFC 4001, see the RFC
itself for full legal notices."
REVISION "200502040000Z"
DESCRIPTION
"Third version, published as RFC 4001. This revision
introduces the InetZoneIndex, InetScopeType, and
InetVersion textual conventions."
REVISION "200205090000Z"
DESCRIPTION
"Second version, published as RFC 3291. This
revision contains several clarifications and
introduces several new textual conventions:
InetAddressPrefixLength, InetPortNumber,
InetAutonomousSystemNumber, InetAddressIPv4z,
and InetAddressIPv6z."
REVISION "200006080000Z"
Daniele, et al. Standards Track [Page 5]
RFC 4001 Internet Network Address Conventions February 2005
DESCRIPTION
"Initial version, published as RFC 2851."
::= { mib-2 76 }
InetAddressType ::= TEXTUAL-CONVENTION
STATUS current
DESCRIPTION
"A value that represents a type of Internet address.
unknown(0) An unknown address type. This value MUST
be used if the value of the corresponding
InetAddress object is a zero-length string.
It may also be used to indicate an IP address
that is not in one of the formats defined
below.
ipv4(1) An IPv4 address as defined by the
InetAddressIPv4 textual convention.
ipv6(2) An IPv6 address as defined by the
InetAddressIPv6 textual convention.
ipv4z(3) A non-global IPv4 address including a zone
index as defined by the InetAddressIPv4z
textual convention.
ipv6z(4) A non-global IPv6 address including a zone
index as defined by the InetAddressIPv6z
textual convention.
dns(16) A DNS domain name as defined by the
InetAddressDNS textual convention.
Each definition of a concrete InetAddressType value must be
accompanied by a definition of a textual convention for use
with that InetAddressType.
To support future extensions, the InetAddressType textual
convention SHOULD NOT be sub-typed in object type definitions.
It MAY be sub-typed in compliance statements in order to
require only a subset of these address types for a compliant
implementation.
Implementations must ensure that InetAddressType objects
and any dependent objects (e.g., InetAddress objects) are
consistent. An inconsistentValue error must be generated
if an attempt to change an InetAddressType object would,
for example, lead to an undefined InetAddress value. In
Daniele, et al. Standards Track [Page 6]
RFC 4001 Internet Network Address Conventions February 2005
particular, InetAddressType/InetAddress pairs must be
changed together if the address type changes (e.g., from
ipv6(2) to ipv4(1))."
SYNTAX INTEGER {
unknown(0),
ipv4(1),
ipv6(2),
ipv4z(3),
ipv6z(4),
dns(16)
}
InetAddress ::= TEXTUAL-CONVENTION
STATUS current
DESCRIPTION
"Denotes a generic Internet address.
An InetAddress value is always interpreted within the context
of an InetAddressType value. Every usage of the InetAddress
textual convention is required to specify the InetAddressType
object that provides the context. It is suggested that the
InetAddressType object be logically registered before the
object(s) that use the InetAddress textual convention, if
they appear in the same logical row.
The value of an InetAddress object must always be
consistent with the value of the associated InetAddressType
object. Attempts to set an InetAddress object to a value
inconsistent with the associated InetAddressType
must fail with an inconsistentValue error.
When this textual convention is used as the syntax of an
index object, there may be issues with the limit of 128
sub-identifiers specified in SMIv2, STD 58. In this case,
the object definition MUST include a 'SIZE' clause to
limit the number of potential instance sub-identifiers;
otherwise the applicable constraints MUST be stated in
the appropriate conceptual row DESCRIPTION clauses, or
in the surrounding documentation if there is no single
DESCRIPTION clause that is appropriate."
SYNTAX OCTET STRING (SIZE (0..255))
InetAddressIPv4 ::= TEXTUAL-CONVENTION
DISPLAY-HINT "1d.1d.1d.1d"
STATUS current
DESCRIPTION
"Represents an IPv4 network address:
Daniele, et al. Standards Track [Page 7]
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Octets Contents Encoding
1-4 IPv4 address network-byte order
The corresponding InetAddressType value is ipv4(1).
This textual convention SHOULD NOT be used directly in object
definitions, as it restricts addresses to a specific format.
However, if it is used, it MAY be used either on its own or in
conjunction with InetAddressType, as a pair."
SYNTAX OCTET STRING (SIZE (4))
InetAddressIPv6 ::= TEXTUAL-CONVENTION
DISPLAY-HINT "2x:2x:2x:2x:2x:2x:2x:2x"
STATUS current
DESCRIPTION
"Represents an IPv6 network address:
Octets Contents Encoding
1-16 IPv6 address network-byte order
The corresponding InetAddressType value is ipv6(2).
This textual convention SHOULD NOT be used directly in object
definitions, as it restricts addresses to a specific format.
However, if it is used, it MAY be used either on its own or in
conjunction with InetAddressType, as a pair."
SYNTAX OCTET STRING (SIZE (16))
InetAddressIPv4z ::= TEXTUAL-CONVENTION
DISPLAY-HINT "1d.1d.1d.1d%4d"
STATUS current
DESCRIPTION
"Represents a non-global IPv4 network address, together
with its zone index:
Octets Contents Encoding
1-4 IPv4 address network-byte order
5-8 zone index network-byte order
The corresponding InetAddressType value is ipv4z(3).
The zone index (bytes 5-8) is used to disambiguate identical
address values on nodes that have interfaces attached to
different zones of the same scope. The zone index may contain
the special value 0, which refers to the default zone for each
scope.
This textual convention SHOULD NOT be used directly in object
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definitions, as it restricts addresses to a specific format.
However, if it is used, it MAY be used either on its own or in
conjunction with InetAddressType, as a pair."
SYNTAX OCTET STRING (SIZE (8))
InetAddressIPv6z ::= TEXTUAL-CONVENTION
DISPLAY-HINT "2x:2x:2x:2x:2x:2x:2x:2x%4d"
STATUS current
DESCRIPTION
"Represents a non-global IPv6 network address, together
with its zone index:
Octets Contents Encoding
1-16 IPv6 address network-byte order
17-20 zone index network-byte order
The corresponding InetAddressType value is ipv6z(4).
The zone index (bytes 17-20) is used to disambiguate
identical address values on nodes that have interfaces
attached to different zones of the same scope. The zone index
may contain the special value 0, which refers to the default
zone for each scope.
This textual convention SHOULD NOT be used directly in object
definitions, as it restricts addresses to a specific format.
However, if it is used, it MAY be used either on its own or in
conjunction with InetAddressType, as a pair."
SYNTAX OCTET STRING (SIZE (20))
InetAddressDNS ::= TEXTUAL-CONVENTION
DISPLAY-HINT "255a"
STATUS current
DESCRIPTION
"Represents a DNS domain name. The name SHOULD be fully
qualified whenever possible.
The corresponding InetAddressType is dns(16).
The DESCRIPTION clause of InetAddress objects that may have
InetAddressDNS values MUST fully describe how (and when)
these names are to be resolved to IP addresses.
The resolution of an InetAddressDNS value may require to
query multiple DNS records (e.g., A for IPv4 and AAAA for
IPv6). The order of the resolution process and which DNS
record takes precedence depends on the configuration of the
resolver.
Daniele, et al. Standards Track [Page 9]
RFC 4001 Internet Network Address Conventions February 2005
This textual convention SHOULD NOT be used directly in object
definitions, as it restricts addresses to a specific format.
However, if it is used, it MAY be used either on its own or in
conjunction with InetAddressType, as a pair."
SYNTAX OCTET STRING (SIZE (1..255))
InetAddressPrefixLength ::= TEXTUAL-CONVENTION
DISPLAY-HINT "d"
STATUS current
DESCRIPTION
"Denotes the length of a generic Internet network address
prefix. A value of n corresponds to an IP address mask
that has n contiguous 1-bits from the most significant
bit (MSB), with all other bits set to 0.
An InetAddressPrefixLength value is always interpreted within
the context of an InetAddressType value. Every usage of the
InetAddressPrefixLength textual convention is required to
specify the InetAddressType object that provides the
context. It is suggested that the InetAddressType object be
logically registered before the object(s) that use the
InetAddressPrefixLength textual convention, if they appear
in the same logical row.
InetAddressPrefixLength values larger than
the maximum length of an IP address for a specific
InetAddressType are treated as the maximum significant
value applicable for the InetAddressType. The maximum
significant value is 32 for the InetAddressType
'ipv4(1)' and 'ipv4z(3)' and 128 for the InetAddressType
'ipv6(2)' and 'ipv6z(4)'. The maximum significant value
for the InetAddressType 'dns(16)' is 0.
The value zero is object-specific and must be defined as
part of the description of any object that uses this
syntax. Examples of the usage of zero might include
situations where the Internet network address prefix
is unknown or does not apply.
The upper bound of the prefix length has been chosen to
be consistent with the maximum size of an InetAddress."
SYNTAX Unsigned32 (0..2040)
InetPortNumber ::= TEXTUAL-CONVENTION
DISPLAY-HINT "d"
STATUS current
DESCRIPTION
"Represents a 16 bit port number of an Internet transport
Daniele, et al. Standards Track [Page 10]
RFC 4001 Internet Network Address Conventions February 2005
layer protocol. Port numbers are assigned by IANA. A
current list of all assignments is available from
RFC, FYI, BCP