path: root/doc/rfc/rfc4001.txt

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.




















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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.




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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:






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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].





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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.



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         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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         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),



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                     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.




































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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











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Full Copyright Statement

   Copyright (C) The Internet Society (2005).

   This document is subject to the rights, licenses and restrictions
   contained in BCP 78, and at www.rfc-editor.org, and except as set
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Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.







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