RFC4001: Textual Conventions for Internet Network Addresses
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Obsoletes:
RFC3291
Related keywords:
(internet network layer addressing information)
(management information base)
(MIB)
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]
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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 <ietfmibs@ops.ietf.org>."
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"
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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
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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:
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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
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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
<http://www.iana.org/>.
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 a port number is unknown, or when the
value zero is used as a wildcard in a filter."
REFERENCE "STD 6 (RFC 768), STD 7 (RFC 793) and RFC 2960"
SYNTAX Unsigned32 (0..65535)
InetAutonomousSystemNumber ::= TEXTUAL-CONVENTION
DISPLAY-HINT "d"
STATUS current
DESCRIPTION
"Represents an autonomous system number that identifies an
Autonomous System (AS). An AS is a set of routers under a
single technical administration, using an interior gateway
protocol and common metrics to route packets within the AS,
and using an exterior gateway protocol to route packets to
other ASes'. IANA maintains the AS number space and has
delegated large parts to the regional registries.
Autonomous system numbers are currently limited to 16 bits
(0..65535). There is, however, work in progress to enlarge the
autonomous system number space to 32 bits. Therefore, this
textual convention uses an Unsigned32 value without a
range restriction in order to support a larger autonomous
system number space."
REFERENCE "RFC 1771, RFC 1930"
SYNTAX Unsigned32
InetScopeType ::= TEXTUAL-CONVENTION
STATUS current
DESCRIPTION
"Represents a scope type. This textual convention can be used
in cases where a MIB has to represent different scope types
and there is no context information, such as an InetAddress
object, that implicitly defines the scope type.
Note that not all possible values have been assigned yet, but
they may be assigned in future revisions of this specification.
Applications should therefore be able to deal with values
not yet assigned."
REFERENCE "RFC 3513"
SYNTAX INTEGER {
-- reserved(0),
Daniele, et al. Standards Track [Page 11]
RFC 4001 Internet Network Address Conventions February 2005
interfaceLocal(1),
linkLocal(2),
subnetLocal(3),
adminLocal(4),
siteLocal(5), -- site-local unicast addresses
-- have been deprecated by RFC 3879
-- unassigned(6),
-- unassigned(7),
organizationLocal(8),
-- unassigned(9),
-- unassigned(10),
-- unassigned(11),
-- unassigned(12),
-- unassigned(13),
global(14)
-- reserved(15)
}
InetZoneIndex ::= TEXTUAL-CONVENTION
DISPLAY-HINT "d"
STATUS current
DESCRIPTION
"A zone index identifies an instance of a zone of a
specific scope.
The zone index MUST disambiguate identical address
values. For link-local addresses, the zone index will
typically be the interface index (ifIndex as defined in the
IF-MIB) of the interface on which the address is configured.
The zone index may contain the special value 0, which refers
to the default zone. The default zone may be used in cases
where the valid zone index is not known (e.g., when a
management application has to write a link-local IPv6
address without knowing the interface index value). The
default zone SHOULD NOT be used as an easy way out in
cases where the zone index for a non-global IPv6 address
is known."
REFERENCE "RFC4007"
SYNTAX Unsigned32
InetVersion ::= TEXTUAL-CONVENTION
STATUS current
DESCRIPTION
"A value representing a version of the IP protocol.
unknown(0) An unknown or unspecified version of the IP
protocol.
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ipv4(1) The IPv4 protocol as defined in RFC 791 (STD 5).
ipv6(2) The IPv6 protocol as defined in RFC 2460.
Note that this textual convention SHOULD NOT be used to
distinguish different address types associated with IP
protocols. The InetAddressType has been designed for this
purpose."
REFERENCE "RFC 791, RFC 2460"
SYNTAX INTEGER {
unknown(0),
ipv4(1),
ipv6(2)
}
END
4. Usage Hints
The InetAddressType and InetAddress textual conventions have been
introduced to avoid over-constraining an object definition by the use
of the IpAddress SMI base type, which is IPv4 specific. An
InetAddressType/InetAddress pair can represent IP addresses in
various formats.
The InetAddressType and InetAddress objects SHOULD NOT be sub-typed
in object definitions. Sub-typing binds the MIB module to specific
address formats, which may cause serious problems if new address
formats need to be introduced. Note that it is possible to write
compliance statements indicating that only a subset of the defined
address types must be implemented to be compliant.
Every usage of the InetAddress or InetAddressPrefixLength textual
conventions must specify which InetAddressType object provides the
context for the interpretation of the InetAddress or
InetAddressPrefixLength textual convention.
It is suggested that the InetAddressType object is logically
registered before the object(s) that use(s) the InetAddress or
InetAddressPrefixLength textual convention. An InetAddressType
object is logically registered before an InetAddress or
InetAddressPrefixLength object if it appears before the InetAddress
or InetAddressPrefixLength object in the conceptual row (which
includes any index objects). This rule allows programs such as MIB
compilers to identify the InetAddressType of a given InetAddress or
InetAddressPrefixLength object by searching for the InetAddressType
object, which precedes an InetAddress or InetAddressPrefixLength
object.
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4.1. Table Indexing
When a generic Internet address is used as an index, both the
InetAddressType and InetAddress objects MUST be used. The
InetAddressType object MUST be listed before the InetAddress object
in the INDEX clause.
The IMPLIED keyword MUST NOT be used for an object of type
InetAddress in an INDEX clause. Instance sub-identifiers are then of
the form T.N.O1.O2...On, where T is the value of the InetAddressType
object, O1...On are the octets in the InetAddress object, and N is
the number of those octets.
There is a meaningful lexicographical ordering to tables indexed in
this fashion. Command generator applications may look up specific
addresses of known type and value, issue GetNext requests for
addresses of a single type, or issue GetNext requests for a specific
type and address prefix.
4.2. Uniqueness of Addresses
IPv4 addresses were intended to be globally unique, current usage
notwithstanding. IPv6 addresses were architected to have different
scopes and hence uniqueness [RFC3513]. In particular, IPv6 "link-
local" unicast addresses are not guaranteed to be unique on any
particular node. In such cases, the duplicate addresses must be
configured on different interfaces. So the combination of an IPv6
address and a zone index is unique [RFC4007].
The InetAddressIPv6 textual convention has been defined to represent
global IPv6 addresses and non-global IPv6 addresses in cases where no
zone index is needed (e.g., on end hosts with a single interface).
The InetAddressIPv6z textual convention has been defined to represent
non-global IPv6 addresses in cases where a zone index is needed
(e.g., a router connecting multiple zones). Therefore, MIB designers
who use InetAddressType/InetAddress pairs do not need to define
additional objects in order to support non-global addresses on nodes
that connect multiple zones.
The InetAddressIPv4z is intended for use in MIB modules (such as the
TCP-MIB) which report addresses in the address family used on the
wire, but where the entity instrumented obtains these addresses from
applications or administrators in a form that includes a zone index,
such as v4-mapped IPv6 addresses.
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The size of the zone index has been chosen so that it is consistent
with (i) the numerical zone index, defined in [RFC4007], and (ii) the
sin6_scope_id field of the sockaddr_in6 structure, defined in RFC
2553 [RFC2553].
4.3. Multiple Addresses per Host
A single host system may be configured with multiple addresses (IPv4
or IPv6), and possibly with multiple DNS names. Thus it is possible
for a single host system to be accessible by multiple
InetAddressType/InetAddress pairs.
If this could be an implementation or usage issue, the DESCRIPTION
clause of the relevant objects must fully describe which address is
reported in a given InetAddressType/InetAddress pair.
4.4. Resolving DNS Names
DNS names MUST be resolved to IP addresses when communication with
the named host is required. This raises a temporal aspect to
defining MIB objects whose value is a DNS name: When is the name
translated to an address?
For example, consider an object defined to indicate a forwarding
destination, and whose value is a DNS name. When does the forwarding
entity resolve the DNS name? Each time forwarding occurs, or just
once when the object was instantiated?
The DESCRIPTION clause of these objects SHOULD precisely define how
and when any required name to address resolution is done.
Similarly, the DESCRIPTION clause of these objects SHOULD precisely
define how and when a reverse lookup is being done, if an agent has
accessed instrumentation that knows about an IP address, and if the
MIB module or implementation requires it to map the IP address to a
DNS name.
5. Table Indexing Example
This example shows a table listing communication peers that are
identified by either an IPv4 address, an IPv6 address, or a DNS name.
The table definition also prohibits entries with an empty address
(whose type would be "unknown"). The size of a DNS name is limited
to 64 characters in order to satisfy OID length constraints.
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peerTable OBJECT-TYPE
SYNTAX SEQUENCE OF PeerEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"A list of communication peers."
::= { somewhere 1 }
peerEntry OBJECT-TYPE
SYNTAX PeerEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"An entry containing information about a particular peer."
INDEX { peerAddressType, peerAddress }
::= { peerTable 1 }
PeerEntry ::= SEQUENCE {
peerAddressType InetAddressType,
peerAddress InetAddress,
peerStatus INTEGER
}
peerAddressType OBJECT-TYPE
SYNTAX InetAddressType
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"The type of Internet address by which the peer
is reachable."
::= { peerEntry 1 }
peerAddress OBJECT-TYPE
SYNTAX InetAddress (SIZE (1..64))
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"The Internet address for the peer. The type of this
address is determined by the value of the peerAddressType
object. Note that implementations must limit themselves
to a single entry in this table per reachable peer.
The peerAddress may not be empty due to the SIZE
restriction.
If a row is created administratively by an SNMP
operation and the address type value is dns(16), then
the agent stores the DNS name internally. A DNS name
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lookup must be performed on the internally stored DNS
name whenever it is being used to contact the peer.
If a row is created by the managed entity itself and
the address type value is dns(16), then the agent
stores the IP address internally. A DNS reverse lookup
must be performed on the internally stored IP address
whenever the value is retrieved via SNMP."
::= { peerEntry 2 }
The following compliance statement specifies that compliant
implementations need only support IPv4/IPv6 addresses without zone
indices. Support for DNS names or IPv4/IPv6 addresses with zone
indices is not required.
peerCompliance MODULE-COMPLIANCE
STATUS current
DESCRIPTION
"The compliance statement of the peer MIB."
MODULE -- this module
MANDATORY-GROUPS { peerGroup }
OBJECT peerAddressType
SYNTAX InetAddressType { ipv4(1), ipv6(2) }
DESCRIPTION
"An implementation is only required to support IPv4
and IPv6 addresses without zone indices."
::= { somewhere 2 }
Note that the SMIv2 does not permit inclusion of objects that are not
accessible in an object group (see section 3.1 in STD 58, RFC 2580
[RFC2580]). It is therefore not possible to refine the syntax of
auxiliary objects that are not accessible. It is suggested that the
refinement be expressed informally in the DESCRIPTION clause of the
MODULE-COMPLIANCE macro invocation.
6. Security Considerations
This module does not define any management objects. Instead, it
defines a set of textual conventions which may be used by other MIB
modules to define management objects.
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Meaningful security considerations can only be written in the MIB
modules that define management objects. This document has therefore
no impact on the security of the Internet.
7. Acknowledgments
This document was produced by the Operations and Management Area
"IPv6MIB" design team. For their comments and suggestions, the
authors would like to thank Fred Baker, Randy Bush, Richard Draves,
Mark Ellison, Bill Fenner, Jun-ichiro Hagino, Mike Heard, Tim
Jenkins, Allison Mankin, Glenn Mansfield, Keith McCloghrie, Thomas
Narten, Erik Nordmark, Peder Chr. Norgaard, Randy Presuhn, Andrew
Smith, Dave Thaler, Kenneth White, Bert Wijnen, and Brian Zill.
8. Changes from RFC 3291 to RFC 4001
The following changes have been made relative to RFC 3291:
o Added a range restriction to the InetAddressPrefixLength textual
convention.
o Added new textual conventions InetZoneIndex, InetScopeType, and
InetVersion.
o Added explicit "d" DISPLAY-HINTs for textual conventions that did
not have them.
o Updated boilerplate text and references.
9. Changes from RFC 2851 to RFC 3291
The following changes have been made relative to RFC 2851:
o Added new textual conventions InetAddressPrefixLength,
InetPortNumber, and InetAutonomousSystemNumber.
o Rewrote the introduction to say clearly that, in general, one
should define MIB tables that work with all versions of IP. The
other approach of multiple tables for different IP versions is
strongly discouraged.
o Added text to the InetAddressType and InetAddress descriptions
requiring that implementations must reject set operations with an
inconsistentValue error if they lead to inconsistencies.
o Removed the strict ordering constraints. Description clauses now
must explain which InetAddressType object provides the context for
an InetAddress or InetAddressPrefixLength object.
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o Aligned wordings with the IPv6 scoping architecture document.
o Split the InetAddressIPv6 textual convention into the two textual
conventions (InetAddressIPv6 and InetAddressIPv6z) and introduced
a new textual convention InetAddressIPv4z. Added ipv4z(3) and
ipv6z(4) named numbers to the InetAddressType enumeration.
Motivations for this change: (i) to enable the introduction of a
textual conventions for non-global IPv4 addresses, (ii) alignment
with the textual conventions for transport addresses, (iii)
simpler compliance statements in cases where support for IPv6
addresses with zone indices is not required, and (iv) to simplify
implementations for host systems that will never have to report
zone indices.
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2578] McCloghrie, K., Perkins, D., and J. Schoenwaelder,
"Structure of Management Information Version 2 (SMIv2)",
STD 58, RFC 2578, April 1999.
[RFC2579] McCloghrie, K., Perkins, D., and J. Schoenwaelder,
"Textual Conventions for SMIv2", STD 58, RFC 2579, April
1999.
[RFC2580] McCloghrie, K., Perkins, D., and J. Schoenwaelder,
"Conformance Statements for SMIv2", STD 58, RFC 2580,
April 1999.
[RFC3513] Hinden, R. and S. Deering, "Internet Protocol Version 6
(IPv6) Addressing Architecture", RFC 3513, April 2003.
[RFC4007] Deering, S., Haberman, B., Jinmei, T., Nordmark, E., and
B. Zill, "IPv6 Scoped Address Architecture", RFC 4007,
February 2005.
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10.2. Informative References
[RFC2553] Gilligan, R., Thomson, S., Bound, J., and W. Stevens,
"Basic Socket Interface Extensions for IPv6", RFC 2553,
March 1999.
[RFC2863] McCloghrie, K. and F. Kastenholz, "The Interfaces Group
MIB", RFC 2863, June 2000.
[RFC3410] Case, J., Mundy, R., Partain, D., and B. Stewart,
"Introduction and Applicability Statements for Internet-
Standard Management Framework", RFC 3410, December 2002.
[RFC3419] Daniele, M. and J. Schoenwaelder, "Textual Conventions for
Transport Addresses", RFC 3419, December 2002.
Daniele, et al. Standards Track [Page 20]
RFC 4001 Internet Network Address Conventions February 2005
Authors' Addresses
Michael Daniele
SyAM Software, Inc.
1 Chestnut St, Suite 3-I
Nashua, NH 03060
USA
Phone: +1 603 598-9575
EMail: michael.daniele@syamsoftware.com
Brian Haberman
Johns Hopkins University Applied Physics Laboratory
11100 Johns Hopkins Road
Laurel, MD 20723-6099
USA
Phone: +1-443-778-1319
EMail: brian@innovationslab.net
Shawn A. Routhier
Wind River Systems, Inc.
500 Wind River Way
Alameda, CA 94501
USA
Phone: +1 510 749-2095
EMail: shawn.routhier@windriver.com
Juergen Schoenwaelder
International University Bremen
P.O. Box 750 561
28725 Bremen
Germany
Phone: +49 421 200-3587
EMail: j.schoenwaelder@iu-bremen.de
Daniele, et al. Standards Track [Page 21]
RFC 4001 Internet Network Address Conventions February 2005
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Daniele, et al. Standards Track [Page 22]