Network Working Group
Request for Comments: 3944
Category: Informational

T. Johnson
U. of North Carolina
S. Okubo
Waseda University
S. Campos
ITU-T
December 2004

H.350 Directory Services

Status of this Memo

This memo provides information for the Internet community. It does not specify an Internet standard of any kind. Distribution of this memo is unlimited.

Copyright Notice

Abstract

The International Telecommunications Union Standardization Sector (ITU-T) has created the H.350 series of Recommendations that specify directory services architectures in support of multimedia conferencing protocols. The goal of the architecture is to 'directory enable' multimedia conferencing so that these services can leverage existing identity management and enterprise directories. A particular goal is to enable an enterprise or service provider to maintain a canonical source of users and their multimedia conferencing systems, so that multiple call servers from multiple vendors, supporting multiple protocols, can all access the same data store.

Because SIP is an IETF standard, the contents of H.350 and H.350.4 are made available via this document to the IETF community. This document contains the entire normative text of ITU-T Recommendations H.350 and H.350.4 in sections 4 and 5, respectively. The remaining sections are included only in this document, not in the ITU-T version.

   1.   Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.   Terminology . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.   Conventions used in this document . . . . . . . . . . . . . .  4
   4.   H.350 . . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
        4.1.  Scope . . . . . . . . . . . . . . . . . . . . . . . . .  4
              4.1.1. Design Goals . . . . . . . . . . . . . . . . . .  6
              4.1.2. Extending the Schema . . . . . . . . . . . . . .  7
        4.2.  commURIObject Definition. . . . . . . . . . . . . . . . 10
              4.2.1. commURIObject. . . . . . . . . . . . . . . . . . 10
              4.2.2. commURI. . . . . . . . . . . . . . . . . . . . . 10
        4.3.  CommObject Definition . . . . . . . . . . . . . . . . . 11
              4.3.1. commObject . . . . . . . . . . . . . . . . . . . 11
              4.3.2. commUniqueId . . . . . . . . . . . . . . . . . . 11
              4.3.3. commOwner. . . . . . . . . . . . . . . . . . . . 12
              4.3.4. commPrivate. . . . . . . . . . . . . . . . . . . 13
        4.4.  CommObject LDIF Files . . . . . . . . . . . . . . . . . 13
              4.4.1. LDIF for commURIObject . . . . . . . . . . . . . 13
              4.4.2. LDIF for commObject. . . . . . . . . . . . . . . 15
        4.5.  H.350 Annex A Indexing Profile. . . . . . . . . . . . . 17
   5.   H.350.4 . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
        5.1.  Scope . . . . . . . . . . . . . . . . . . . . . . . . . 17
              5.1.1. Extending the schema . . . . . . . . . . . . . . 18
        5.2.  Object class definitions. . . . . . . . . . . . . . . . 18
              5.2.1. SIPIdentity. . . . . . . . . . . . . . . . . . . 18
              5.2.2. SIPIdentitySIPURI. . . . . . . . . . . . . . . . 19
              5.2.3. SIPIdentityRegistrarAddress. . . . . . . . . . . 19
              5.2.4. SIPIdentityProxyAddress. . . . . . . . . . . . . 20
              5.2.5. SIPIdentityAddress . . . . . . . . . . . . . . . 21
              5.2.6. SIPIdentityPassword. . . . . . . . . . . . . . . 21
              5.2.7. SIPIdentityUserName. . . . . . . . . . . . . . . 22
              5.2.8. SIPIdentityServiceLevel. . . . . . . . . . . . . 23
        5.3.  SIPIdentity LDIF Files. . . . . . . . . . . . . . . . . 23
        5.4.  H.350.4 Annex A Indexing profile. . . . . . . . . . . . 26
   6.   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 26
   7.   Security Considerations . . . . . . . . . . . . . . . . . . . 27
   8.   References. . . . . . . . . . . . . . . . . . . . . . . . . . 28
        8.1.  Normative References. . . . . . . . . . . . . . . . . . 28
        8.2.  Informative References. . . . . . . . . . . . . . . . . 28
   9.   Relationship to Other Specifications. . . . . . . . . . . . . 29
   10.  Authors' Addresses. . . . . . . . . . . . . . . . . . . . . . 29
        Full Copyright Statement. . . . . . . . . . . . . . . . . . . 30

1. Scope

H.350 architectures are not intended to change the operation of multimedia conferencing protocols in any way. Rather, they are meant to standardize the way the already defined protocol elements are stored in a directory, so that they can be accessed in a standardized manner.

In the H.350 series, Recommendation H.350 specifies the base architecture and object classes, while subordinate Recommendations specify elements that are specific to individual protocols. Currently, the Recommendations include:

   H.350   - Directory Services Architecture for Multimedia Conferencing
   H.350.1 - Directory Services Architecture for H.323
   H.350.2 - Directory Services Architecture for H.235
   H.350.3 - Directory Services Architecture for H.320
   H.350.4 - Directory Services Architecture for SIP
   H.350.5 - Directory Services Architecture for Non-Standard Protocols

Because SIP is an IETF standard, the contents of H.350 and H.350.4 are made available via this document to the IETF community.

2. Terminology

The following terms are used throughout the document:

call server: a protocol-specific signalling engine that routes video or voice calls on the network. In H.323 this entity is a gatekeeper. In SIP, this entity is a SIP Proxy Server. Note that not all signalling protocols use a call server.

endpoint: a logical device that provides video and/or voice media encoding/decoding, and signalling functions. Examples include:

a group teleconferencing appliance that is located in a conference room

an IP telephone.

a software program that takes video and voice from a camera and microphone and encodes it and applies signalling using a host computer.

enterprise directory: A canonical collection of information about users in an organization. Typically this information is collected from a variety of organizational units to create a whole. For example, Human Resources may provide name and address, Telecommunications may provide the telephone number, Information Technology may provide the email address, etc. For the purposes of this architecture, it is assumed that an enterprise directory is accessible via LDAP.

White Pages: An application that allows end users to look up the address of another user. This may be web-based or use some other user interface.

3. Conventions used in this document

Conventions in this document conform to ITU-T guidelines. In this Recommendation, the following conventions are used:

"Shall" indicates a mandatory requirement.

"Should" indicates a suggested but optional course of action.

"May" indicates an optional course of action rather than a recommendation that something take place.

References to clauses, sub clauses, annexes and appendices refer to those items within this Recommendation unless another specification is explicitly listed.

4. H.350

The normative text of H.350 is reproduced in this section.

4.1. Scope

This Recommendation describes a directory services architecture for multimedia conferencing using LDAP. Standardized directory services can support association of persons with endpoints, searchable white pages, and clickable dialling. Directory services can also assist in the configuration of endpoints, and user authentication based on authoritative data sources. This document describes a standardized LDAP schema to represent endpoints on the network and associate those endpoints with users. It discusses design and implementation considerations for the inter-relation of video and voice-specific directories, enterprise directories, call servers and endpoints.

The use of a common, authoritative data source for call server, endpoint, user, authentication and white pages information is an important aspect of large scale multimedia conferencing environments. Without a common data source, service providers must create separate processes to manage each of these functions. By standardizing the LDAP schema used to represent the underlying data, products from different system vendors can be deployed together to create an overall application environment. For example, a white pages search engine developed by one provider could serve directory information to IP telephones produced by a second provider, with signalling managed by a call server produced by yet a third provider. Each of these disparate systems can access the same underlying data source, reducing or eliminating the need to coordinate separate management of each system. A significant benefit to the user is that the management of this data can be incorporated into existing customer management tools, allowing for quick and flexible scaling up of applications. Indeed, many technology providers have already incorporate LDAP into their products, but have been forced to do so without benefit of a standardized schema. This Recommendation represents an effort to standardize those representations to improve interoperability and performance.

While URLs are already standardized for several conferencing protocols, their representation in a directory is not. This Recommendation supports a standardized way for URLs to be searched and located. This is a necessary step to support 'clickable dialling'.

Management of endpoint configurations can be improved if the correct settings are stored by the service provider in a location that is accessible to both service provider and endpoint. LDAP provides a convenient storage location that can be accessed by both call server and endpoint; thus it is possible to use the directory to support endpoint configuration, which is important for simplified operation and supporting user mobility. Note that other technologies also support endpoint configuration, notably the use of SNMP for complete configuration and SRV records for obtaining registration server addresses. Therefore, H.350 should be viewed not as an authoritative endpoint configuration architecture, but rather one tool that can assist with this task. Note that the use of H.350 has as a feature endpoint specific configuration, where it is desirable that each endpoint has a unique configuration.

This architecture uses a generic object class, called commObject, to represent attributes common to any video or voice protocol. Auxiliary classes represent specific protocols, such as H.323, H.235, or H.320, as described in the H.350.x series of Recommendations. Multiple H.350.x classes can be combined to represent endpoints that support more than one protocol. For example, endpoints that support H.323, H.235 and H.320 would include H.350, H.350.1, H.350.2, and H.350.3 in their LDAP representations. Further, each entry should contain commObject to serve as the entry's structural object class.

There are two basic components in the architecture. The commURI object is a class whose only purpose is to link a person or resource to a commObject. By placing a commURI 'pointer' in an individual's directory entry, that individual becomes associated with the particular targeted commObject. Similarly, commObject contains a pointer, called commOwner, which points to the individual or resource that is associated with the commObject. In this way, people or resources can be associated with endpoints. The only change required in the enterprise directory is the addition of the simple object class commURI. CommObject data may be instantiated in the same or in entirely separate directories, thus allowing flexibility in implementation.

4.1.1. Design Goals

Large-scale deployments of IP video and voice services have demonstrated the need for complementary directory services middleware. Service administrators need call servers that are aware of enterprise directories to avoid duplication of account management processes. Users need 'white pages' to locate other users with whom they wish to communicate. All of these processes should pull their information from canonical data sources in order to reduce redundant administrative processes and ensure information accuracy. The following design criteria are established for this architecture. The architecture will:

   1)   enable endpoint information to be associated with people.
   
        Alternately it enables endpoint information to be associated
        with resources such as conference rooms or classrooms;
   
   2)   enable online searchable "white pages" where dialling
        information (e.g., endpoint addresses) can be found, along with
        other "traditional" directory information about a user, such as
        name, address, telephone, email, etc.;
   
   3)   enable all endpoint information to be stored in a canonical data
        source (the Directory), rather than local to the call server, so
        that endpoints can be managed through manipulations of an
        enterprise directory, rather than by direct entry into the call
        server;
   
   4)   support the creation of very large-scale distributed
        directories.  These include white pages "portals" that allow
        searching for users across multiple institutional directories.
        In this application, each enterprise directory registers itself
        with (or is unknowingly discovered by) a directory of
        directories that is capable of searching across multiple LDAP
        directories;
   
   5)   be able to support multiple instances of endpoints per user or
        resource;
   
   6)   represent endpoints that support more than one protocol, for
        example, endpoints that are both H.320 and H.323;
   
   7)   store enough information about endpoint configuration so that
        correct configuration settings can be documented to end users on
        a per-endpoint basis, as a support tool, or loaded automatically
        into the endpoint;
   
   8)   be extendible as necessary to allow implementation-specific
        attributes to be included;
   
   9)   be non-invasive to the enterprise directory, so that support for
        multimedia conferencing can be added in a modular fashion
        without significant changes to the enterprise directory.

The scope of this Recommendation does not include extensions of functionality to protocols as defined within the protocols themselves. It is not the intent of the Recommendation to add features, but merely to represent existing protocol attributes. The exception to this case is when functionality is implied by the directory itself, such as the commPrivate attribute.

4.1.2. Extending the Schema

H.350 object classes may be extended as necessary for specific implementations. For example, a class may be extended to support billing reference codes. Extensions to the schema are not considered as part of the Recommendation and do not signify compliance.

In some cases it may be necessary to extend the H.350 schemas in order to represent more information than is supported by the Recommendations. This may be important for developers that implement proprietary endpoint functionality that needs to be represented by attributes in the directory. It may also be important for enterprise applications. For example 'modelNumber', and 'accountNumber' are examples of attributes that are not defined in the Recommendation but may be useful if implemented. Adding attributes to this architecture must be done in a way that does not break compatibility with this Recommendation.

A full discussion of schema design and extension is beyond the scope of this Recommendation. See IETF RFC 2252 for details. Two basic approaches to schema extension that do not break compatibility with this Recommendation, are extension through subclass and extension through the use of auxiliary classes.

4.1.2.1. Extension Through Subclass

It is possible to create a subclass of an existing predefined object class in order to add new attributes to it. To create a subclass, a new object class must be defined, that is a subclass of the existing one, by indicating in the definition of the new class that the existing class is its superior. Once the subclass is created, new attributes can be defined within it.

The following example shows how the commObject class can be subclassed in order to add an attribute to represent a billing account and a billing manager.

objectclass ( BillingInfo-OID
NAME 'BillingInfo'
DESC 'Billing Reference Information'
SUP commObject STRUCTURAL
MAY ( BillingAccount $ BillingManager $ )
)

Note that BillingInfo-OID must be replaced by an actual OID. Also note that, whenever a structural class is extended, its subclass must also be structural.

The following sample entry shows the newly created attributes. This example also uses ITU-T Rec. H.350.1 for h323Identity.

   dn: commUniqueId=2000,ou=h323identity, dc=company, dc=com
   objectclass: top
   objectclass: commObject
   objectclass: h323Identity
   
   objectclass: BillingInfo
   commUniqueId: 2000
   BillingAccount: 0023456
   BillingManager: John Smith

Note that this example and approach demonstrate extension of the general commObject object class, and not any individual H.350.x classes. If it is desired to extend an H.350.x auxiliary class, then that should be accomplished through the definition of additional auxiliary classes that support the desired attributes, as described in section 4.1.2.2.

4.1.2.2. Extension Through The Use Of Auxiliary Classes

It is possible to add attributes to an LDAP entry by defining an auxiliary class containing the new attributes and applying those attributes to instantiated values in the directory. The auxiliary class will not be subclassed from any existing object class. Note that it should have the special class top as its superior. The following example creates the same billing account and billing manager attributes as the previous example, but does so by defining them in their own auxiliary class.

objectclass ( BillingInfo-OID
NAME 'BillingInfo'
DESC 'Billing Reference Information'
SUP top AUXILIARY
MAY ( BillingAccount $ BillingManager $ )
)

Note how the superior was changed from commObject to top and the object class changed from being a structural to auxiliary.

It is recommended that all attributes in the auxiliary class be optional rather than mandatory. In this way, the auxiliary object class itself can be associated with an entry regardless of whether any values for its attributes are present.

The following example shows a sample endpoint that utilizes the new auxiliary class and attributes. This example also uses H.350.1 for h323Identity.

   dn: commUniqueId=2000,ou=h323identity, dc=company, dc=com
   objectclass: top
   objectclass: commObject
   objectclass: BillingInfo
   commUniqueId: 2000
   BillingAccount: 0023456
   BillingManager: John Smith

4.1.2.3. Object Identifiers

An attribute's Object Identifier (OID) is a unique numerical identifier usually written as a sequence of integers separated by dots. For example, the OID for the commUniqueId is 0.0.8.350.1.1.2.1.1. All attributes must have an OID. OIDs can be obtained from anyone who has one and is willing to delegate a portion of it as an arc, keeping a record of the arc to avoid duplication. Further, the Internet Assigned Numbers Authority (IANA) gives out OIDs to any organization that asks.

4.2. commURIObject Definition

Auxiliary object class that contains the commURI attribute. This attribute is added to a person or resource object to associate one or more commObject instances with that object. Its values are LDAP URIs that point to the associated commObjects, for example, to a user's H.323 conferencing station and SIP IP phone. Note that multiple instances of commURI need not point to the same commObject directory. In fact, each commURI instance could point to an endpoint managed by a different service provider.

4.2.1. commURIObject

OID: 0.0.8.350.1.1.1.2.1
objectclasses: (0.0.8.350.1.1.1.2.1
NAME 'commURIObject'
DESC 'object that contains the URI attribute type'
SUP top AUXILIARY
MAY ( commURI )
)

4.2.2. commURI

   OID: 0.0.8.350.1.1.1.1.1
   attributetypes:( 0.0.8.350.1.1.1.1.1
   NAME 'commURI'
   DESC 'Labeled URI format to point to the distinguished name of the
   commUniqueId'
   EQUALITY caseExactMatch
   SYNTAX 1.3.6.1.4.1.1466.115.121.1.15 )
   Application utility class
        Standard
   
   Number of values
        multi
   Definition
        Labelled URI containing an LDAP URL identifying the directory
   containing the referenced commObject instance.  The search filter
   specified by this LDAP URL shall specify an equality search of the
   commUniqueId attribute of the commObject class.
   Permissible values (if controlled)
   Notes
        Used to find the endpoint of the user in question.  The label
   field may be used to represent the function of the endpoint, such as
   'home IP phone' or 'desktop video' for user interface display
   purposes.
        Note that the label portion of the field may contain spaces as
   in the example below showing 'desktop video'.
   Semantics
   Example applications for which this attribute would be useful
   Example (LDIF fragment)
   commURI:
   ldap://directory.acme.com/dc=acme,dc=com??sub?(commUniqueId=bob)
   desktop video

4.3. CommObject Definition

Abstraction of video or voice over IP device. The commObject class permits an endpoint (H.323 endpoint or SIP user agent or other protocol endpoint) and all their aliases to be represented by a single entry in a directory. Note that every directory entry should contain commObject as the entry's structural object class. That entry may also contain H.350.x auxiliary classes.

4.3.1. commObject

OID: 0.0.8.350.1.1.2.2.1
objectclasses: (0.0.8.350.1.1.2.2.1
NAME 'commObject'
DESC 'object that contains the Communication attributes'
SUP top STRUCTURAL
MUST commUniqueId
MAY ( commOwner $ commPrivate )
)

4.3.2. commUniqueId

   OID: 0.0.8.350.1.1.2.1.1
   attributetypes: (0.0.8.350.1.1.2.1.1
   NAME 'commUniqueId'
   DESC 'To hold the endpoints unique Id'
   EQUALITY caseIgnoreIA5Match
   SUBSTR caseIgnoreIA5SubstringsMatch
   SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )
   Application utility class
        standard
   Number of values
        multi
   Definition
        The endpoint's unique ID.
   Permissible values (if controlled)
   Notes
        This is the RDN of this object.  In practice, there will always
   be one and only one commUniqueId for every endpoint.  This attribute
   uniquely identifies an endpoint in the commObject directory.  It must
   be unique within that directory, but need not be unique globally.
   This attribute has no relationship to the enterprise directory.
   Semantics
   Example applications for which this attribute would be useful
   Example (LDIF fragment)
   commUniqueId: bob

4.3.3. commOwner

   OID: 0.0.8.350.1.1.2.1.2
   attributetypes: 0.0.8.350.1.1.2.1.2
   NAME 'commOwner'
   DESC 'Labeled URI to point back to the original owner'
   EQUALITY caseExactMatch
   SYNTAX 1.3.6.1.4.1.1466.115.121.1.15 )
   Application utility class
        Standard
   Number of values
        multi
   Definition
        Labelled URI format to point back to the person or resource
   object associated with this entry.
   Permissible values (if controlled)
   Notes
        Used as a reverse entry finder of the owner(s).  This attribute
   may point to groups.  Note that this URI can point to a cn, but in
   applications where it is desired to bind authentication information
   across both the commObject and enterprise directories, it may be
   desirable that commOwner points to a dn rather than a cn, thus
   uniquely identifying the owner of the commObject.
   Semantics
   Example applications for which this attribute would be useful
   Example (LDIF fragment)
   commOwner:
   ldap://directory.acme.com/dc=acme,dc=com??sub?(cn=bob%20smith)
   commOwner: uid=bob,ou=people,dc=acme,dc=com

4.3.4. commPrivate

   OID: 0.0.8.350.1.1.2.1.3
   attributetypes: (0.0.8.350.1.1.2.1.3
   NAME 'commPrivate'
   DESC 'To decide whether the entry is visible to world or not'
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )
   Application utility class
        Standard
   Number of values
        multi
   Definition
        To be used by the user and indicate privacy options for an
   endpoint, i.e., unlisted number.
   Permissible values (if controlled)
   Notes
        This attribute is defined as Boolean.  Future version of this
   Recommendation may develop a controlled vocabulary for this
   attribute to accommodate multiple types of privacy.
   Semantics
   Example applications for which this attribute would be useful
   Example (LDIF fragment)
   commPrivate: true

4.4. CommObject LDIF Files

This section contains a schema configuration file for commURIObject and commObject that can be used to configure an LDAP server to support these classes.

4.4.1. LDIF for commURIObject

# Communication Object Schema
#
# Schema for Representing Communication Objects in an LDAP Directory #
# Abstract
#
# This document defines the schema for representing Communication # objects in an LDAP directory [LDAPv3]. It defines schema elements # to represent a communication object URI [commURIObject].
#
#
#

#                     .1 = Communication related work
#                     .1.1 = commURIObject
#                     .1.1.1 = attributes
#                     .1.1.2 = objectclass
#                     .1.1.3 = syntax
#
# Attribute Type Definitions
#
#    The following attribute types are defined in this document:
#
#        commURI
dn: cn=schema
changetype: modify
#
# if you need to change the definition of an attribute,
#            then first delete and re-add in one step
#
# if this is the first time you are adding the commObject
# objectclass using this LDIF file, then you should comment
# out the delete attributetypes modification since this will
# fail.  Alternatively, if your ldapmodify has a switch to continue
# on errors, then just use that switch -- if you're careful
#
delete: attributetypes
attributetypes: (0.0.8.350.1.1.1.1.1 NAME 'commURI' )
-
#
# re-add the attributes -- in case there is a change of definition
#
#
add: attributetypes
attributetypes: (0.0.8.350.1.1.1.1.1
     NAME 'commURI'
     DESC 'Labeled URI format to point to the distinguished name of
the commUniqueId'
     EQUALITY caseExactMatch
     SYNTAX 1.3.6.1.4.1.1466.115.121.1.15 )
-
# Object Class Definitions
#
#    The following object classes are defined in this document:
#
#        commURIObject
#
# commURIObject
#
#    This auxiliary object class represents a URI attribute type
#

#
delete: objectclasses
objectclasses: (0.0.8.350.1.1.1.2.1 NAME 'commURIObject' )
-
add: objectclasses
objectclasses: (0.0.8.350.1.1.1.2.1
     NAME 'commURIObject'
     DESC 'object that contains the URI attribute type'
     SUP top AUXILIARY
     MAY ( commURI )
        )
-
#
# end of LDIF
#

4.4.2. LDIF for commObject

# Communication Object Schema
#
# Schema for Representing Communication Objects in an LDAP Directory
#
# Abstract
#
# This document defines the schema for representing Communication
# objects in an LDAP directory [LDAPv3].  It defines schema elements
# to represent a communication object [commObject].
#
#
#                     .1 = Communication related work
#                     .1.2 = commObject
#                     .1.2.1 = attributes
#                     .1.2.2 = objectclass
#                     .1.2.3 = syntax
#
#
# Attribute Type Definitions
#
#    The following attribute types are defined in this document:
#
#        commUniqueId
#        commOwner
#        commPrivate
dn: cn=schema
changetype: modify
#
# if you need to change the definition of an attribute,
#            then first delete and re-add in one step
#
# if this is the first time you are adding the commObject
# objectclass using this LDIF file, then you should comment
# out the delete attributetypes modification since this will
# fail. Alternatively, if your ldapmodify has a switch to continue
# on errors, then just use that switch -- if you're careful
#
delete: attributetypes
attributetypes: (0.0.8.350.1.1.2.1.1 NAME 'commUniqueId' )
attributetypes: (0.0.8.350.1.1.2.1.2 NAME 'commOwner' )
attributetypes: (0.0.8.350.1.1.2.1.3 NAME 'commPrivate' )
-
#
# re-add the attributes -- in case there is a change of definition
#
#
add: attributetypes
attributetypes: (0.0.8.350.1.1.2.1.1
     NAME 'commUniqueId'
     DESC 'To hold the endpoints unique Id'
     EQUALITY caseIgnoreIA5Match
     SUBSTR caseIgnoreIA5SubstringsMatch
     SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )
attributetypes: (0.0.8.350.1.1.2.1.2
     NAME 'commOwner'
     DESC 'Labeled URI to point back to the original owner'
     EQUALITY caseExactMatch
     SYNTAX 1.3.6.1.4.1.1466.115.121.1.15 )
attributetypes: (0.0.8.350.1.1.2.1.3
     NAME 'commPrivate'
     DESC 'To decide whether the entry is visible to world or not'
     SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )
-
# Object Class Definitions
#
#    The following object classes are defined in this document:
#
#        commObject
#
# commObject
#
#
delete: objectclasses
objectclasses: (0.0.8.350.1.1.2.2.1 NAME 'commObject' )
-
add: objectclasses
objectclasses: (0.0.8.350.1.1.2.2.1
     NAME 'commObject'
     DESC 'object that contains the Communication attributes'
     SUP top STRUCTURAL
     MUST commUniqueId
     MAY ( commOwner $ commPrivate )
     )
-
#
# end of LDIF
#

4.5. H.350 Annex A Indexing Profile

Indexing of attributes is an implementation-specific activity and depends upon the desired application. Non-indexed attributes can result in search times sufficiently long to render some applications unusable. Notably, user and alias lookup should be fast. The Annex A Indexing Profile describes an indexing configuration for commObject directories that will be optimized for use in directory of directories applications. Use of this profile is optional.

commURI:

            no recommendation

commUniqueId:

                 equality

commOwner:

              presence

commPrivate:

                presence

5. H.350.4

The normative text of H.350 is reproduced in this section.

5.1. Scope

This Recommendation describes an LDAP directory services architecture for multimedia conferencing using SIP. In particular, it defines an LDAP schema to represent SIP User Agents (UAs) on the network and associate those endpoints with users.

This Recommendation is intended to supplement the CommObject directory architecture as discussed in ITU-T Rec. H.350, and not intended to be used as a stand-alone architecture. The implementation of this LDAP schema, together with the use of the H.350 CommObject architecture, facilitates the integration of SIP User Agents and conferencing devices into existing Enterprise Directories, thus allowing the user to perform white page lookups and access clickable dialling supported by SIP devices. The primary reasons for implementing this schema include those listed in ITU-T

Rec. H.350 (the CommObject class definition) as they apply specifically to the use of SIP UAs, and to facilitate vendors making SIP services more readily available to their users.

The scope of this Recommendation includes recommendations for the architecture to integrate endpoint information for endpoints using SIP into existing enterprise directories and white pages.

The scope of this Recommendation does not include normative methods for the use of the LDAP directory itself or the data it contains. The purpose of the schema is not to represent all possible data elements in the SIP protocol, but rather to represent the minimal set required to accomplish the design goals enumerated in ITU-T Rec. H.350.

Note that SIP provides well-defined methods for discovering registrar addresses and locating users on the network. Some of the attributes defined here are intended for more trivial or manual implementations and may not be needed for all applications. For example, SIPIdentityRegistrarAddress and SIPIdentityAddress may not be needed for many applications, but are included here for completeness. Thus, SIPIdentitySIPURI is the primary attribute of interest that will be served out, especially for white page directory applications.

5.1.1. Extending the schema

The SIPIdentity classes may be extended as necessary for specific implementations. See the base of ITU-T Rec. H.350 for a discussion on schema extension.

5.2. Object class definitions

The SIPIdentity object class represents SIP User Agents (UAs). It is an auxiliary class and is derived from the commObject class, which is defined in the ITU-T Rec. H.350.

5.2.1. SIPIdentity

   OID: 0.0.8.350.1.1.6.2.1
   objectclasses: (0.0.8.350.1.1.6.2.1
   NAME 'SIPIdentity'
   DESC 'SIPIdentity object'
   SUP top AUXILIARY
   MAY ( SIPIdentitySIPURI $ SIPIdentityRegistrarAddress $
      SIPIdentityProxyAddress $ SIPIdentityUserName $
      SIPIdentityPassword $ SIPIdentityServiceLevel $
      userSMIMECertificate )
   )

5.2.2. SIPIdentitySIPURI

   OID: 0.0.8.350.1.1.6.1.1
   attributetypes: (0.0.8.350.1.1.6.1.1
   NAME 'SIPIdentitySIPURI'
   DESC 'Universal Resource Indicator of the SIP UA'
   EQUALITY caseExactMatch
   SUBSTR caseExactSubstringsMatch
   SYNTAX 1.3.6.1.4.1.1466.115.121.1.15 )
   Application utility class
        standard
   Number of values
        multi
   Definition
        Uniform Resource Identifier that identifies a communication
   resource in SIP.  Usually contains a user name and a host name and is
   often similar in format to an email address.
   Permissible values (if controlled)
   Notes
        This URI may institute SIP or SIPS (secure).  In the event that
   SIPS is instituted, the URI must reflect that it is using SIPS as
   opposed to SIP.  See Examples below.
   Semantics
   Example applications for which this attribute would be useful
        Online representation of most current listing of a user's
   SIP(S) UA.
   Example
   SIPIdentitySIPURI: sip:alice@foo.com          // SIP example
   SIPIdentitySIPURI: sip:alice@152.2.158.212    // SIP example
   SIPIdentitySIPURI: sips:bob@birmingham.edu    // SIPS example

5.2.3. SIPIdentityRegistrarAddress

   OID: 0.0.8.350.1.1.6.1.2
   attributetypes: (0.0.8.350.1.1.6.1.2
   NAME 'SIPIdentityRegistrarAddress'
   DESC 'specifies the location of the registrar'
   EQUALITY caseIgnoreIA5Match
   SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )
   Application utility class
        Standard
   Number of values
        multi
   Definition
        Address for the domain to which the server that handles
   REGISTER requests and forwarding to the location server for a
   particular domain belongs.
   Permissible values (if controlled)
   Notes
        Note that RFC 3261 states that user agents can discover their
   registrar address by configuration, using the address-of-record, or
   by multicast.  The first scenario, by configuration, is noted as out
   of scope for RFC 3261.  This attribute may be used for the first
   scenario.  It can be accomplished manually, (e.g., a web page that
   displays a user's correct registrar address) or automatically with
   an H.350.4 aware user agent.
   Semantics
   Example applications for which this attribute would be useful
        white pages, a web page that displays a user's correct
   configuration information.
   Example (LDIF fragment)
   SIPIdentityRegistrarAddress: 152.2.15.22     //IP address example
   SIPIdentityRegistrarAddress: sipregistrar.unc.edu  //FQDN example

5.2.4. SIPIdentityProxyAddress

   OID: 0.0.8.350.1.1.6.1.3
   attributetypes: (0.0.8.350.1.1.6.1.3
   NAME 'SIPIdentityProxyAddress'
   DESC 'Specifies the location of the SIP Proxy'
   EQUALITY caseIgnoreIA5Match
   SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )
   Application utility class
        Standard
   Number of values
        multi
   Definition
        Address which specifies the domain location of SIP proxy within
   a domain.  RFC 3261 defines the role of the SIP proxy.
   Permissible values (if controlled)
   Notes
        SIP User Agents are not REQUIRED to use a proxy, but will in
   many cases.
   Semantics
   Example applications for which this attribute would be useful
        white pages, a web page that displays a user's correct
   configuration information.
   Example (LDIF fragment)
   SIPIdentityProxyAddress: 172.2.13.234     //IP address example
   SIPIdentityProxyAddress: sipproxy.unc.edu  //FQDN example

5.2.5. SIPIdentityAddress

   OID: 0.0.8.350.1.1.6.1.4
   attributetypes: (0.0.8.350.1.1.6.1.4
   NAME 'SIPIdentityAddress'
   DESC 'IP address or FQDN of the UA'
   EQUALITY caseIgnoreIA5Match
   SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )
   Application utility class
        standard
   Number of values
        multi
   Definition
        Specifies the IP address or fully qualified domain name of the
   UA.
   Permissible values (if controlled)
   Notes
        This attribute may be useful for applications in which UA to UA
   communication is direct, not involving a proxy or registrar.
   Example applications for which this attribute would be useful
        A web page that displays a user's proper user agent
   configuration information.
   Example (LDIF fragment)
   SIPIdentityAddress: 152.2.121.36       // IP address example
   SIPIdentityAddress: ipPhone.foo.org    // FQDN example

5.2.6. SIPIdentityPassword

   OID: 0.0.8.350.1.1.6.1.5
   attributetypes: (0.0.8.350.1.1.6.1.5
   NAME 'SIPIdentityPassword'
   DESC 'The user agent SIP password '
   EQUALITY octetStringMatch
   SYNTAX 1.3.6.1.4.1.1466.115.121.1.40 )
   Application utility class
        Standard
   Number of values
        multi
   Definition
        The SIP user agent's password, used for the HTTP digest
   authentication scheme as defined in RFC 2617.
   Permissible values (if controlled)
   Notes
        Because RFC 2069, which was made obsolete by RFC 2617, was used
   as the basis for HTTP Digest in RFC 2543, any SIP servers supporting
   RFC 2617 must ensure backward compatibility with RFC 2069.
        This SIPIdentityUserName, together with SIPIdentityPassword,
   are reserved for the purpose of use with Digest Access
   Authentication, and not intended for use with Basic Authentication
   methods.
        LDAP provides one method to store user passwords for reference.
   If passwords are stored in LDAP it makes the LDAP server a
   particularly valuable target for attack.  Implementors are encouraged
   to exercise caution and implement appropriate security procedures
   such as encryption, access control, and transport layer security for
   access to this attribute.
   Semantics
   Example applications for which this attribute would be useful
   Example (LDIF fragment)
   SIPIdentityPassword: 36zxJmCIB18dM0FVAj

5.2.7. SIPIdentityUserName

   OID: 0.0.8.350.1.1.6.1.6
   attributetypes: (0.0.8.350.1.1.6.1.6
   NAME 'SIPIdentityUserName'
   DESC 'The user agent user name.'
   EQUALITY caseIgnoreMatch
   SUBSTR caseIgnoreSubstringsMatch
   SYNTAX 1.3.6.1.4.1.1466.115.121.1.15 )
   Application utility class
        Standard
   Number of values
        multi
   Definition
        The SIP user agent's user name, used for the HTTP digest
   authentication scheme as defined in RFC 2617.
   Permissible values (if controlled)
   Notes
        Because RFC 2069, which was made obsolete by RFC 2617, was used
   as the basis for HTTP Digest Authentication in RFC 2543, any SIP
   servers supporting HTTP Digest Authentication as defined in RFC 2617
   must ensure backward compatibility with RFC 2069.
        This SIPIdentityUserName, together with SIPIdentityPassword,
   are reserved for the purpose of use with Digest Access
   Authentication, and not intended for use with Basic Authentication
   methods.
        Note that in many cases the user name will be parsed from the
   user@proxy.domain portion of the SIP URI.  In that case it may not be
   necessary to populate this attribute.
   Semantics
   Example applications for which this attribute would be useful
   Example (LDIF fragment)
   SIPIdentityUserName: nelkhour

5.2.8. SIPIdentityServiceLevel

   OID: 0.0.8.350.1.1.6.1.7
   attributetypes: (0.0.8.350.1.1.6.1.7
   NAME 'SIPIdentityServiceLevel'
   DESC 'To define services that a user can belong to.'
   EQUALITY caseIgnoreIA5Match
   SUBSTR caseIgnoreIA5SubstringsMatch
   SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )
   Application utility class
        Standard
   Number of values
        multi
   Definition
        This describes the level of services a user can belong to.
   Permissible values (if controlled)
   Notes
        This attribute does not represent a data element found in SIP.
   SIP itself does not support distinctions in service levels.  Instead,
   this attribute provides a mechanism for the storage of service level
   information directly in LDAP.  This mapping allows service providers
   to adapt to an existing LDAP directory without changing the values
   of the SIPIdentityServiceLevel instances in the directory.
   Semantics
   Example applications for which this attribute would be useful
   Example (LDIF fragment)
   SIPIdentityServiceLevel: premium

5.3. SIPIdentity LDIF Files

This clause contains a schema configuration file for SIPIdentity that can be used to configure an LDAP server to support this class.

# SIPIdentity Object Schema
#
# Schema for representing SIPIdentity Object in an LDAP Directory
#
# Abstract
#
# This Recommendation defines the schema for representing
SIPIdentity
# object in an LDAP directory [LDAPv3].  It defines schema elements
# to represent an SIPIdentity object [SIPIdentity].
#
#                     .1 = Communication related work
#                     .1.6 = SIPIdentity
#                     .1.6.1 = attributes
#                     .1.6.2 = objectclass

#                     .1.6.3 = syntax
#
#
#
# Attribute Type Definitions
#
#    The following attribute types are defined in this
Recommendation:
#
#     SIPIdentitySIPURI
#     SIPIdentityRegistrarAddress
#     SIPIdentityProxyAddress
#     SIPIdentityAddress
#     SIPIdentityPassword
#     SIPIdentityUserName
#     SIPIdentityServiceLevel
dn: cn=schema
changetype: modify
#
# if you need to change the definition of an attribute,
#            then first delete and re-add in one step
#
# if this is the first time you are adding the SIPIdentity
# objectclass using this LDIF file, then you should comment
# out the delete attributetypes modification since this will
# fail.  Alternatively, if your ldapmodify has a switch to continue
# on errors, then just use that switch -- if you are careful
#
delete: attributetypes
attributetypes: (0.0.8.350.1.1.6.1.1 NAME 'SIPIdentitySIPURI' )
attributetypes: (0.0.8.350.1.1.6.1.2 NAME 'SIPIdentityRegistrarAddress')
attributetypes: (0.0.8.350.1.1.6.1.3 NAME 'SIPIdentityProxyAddress')
attributetypes: (0.0.8.350.1.1.6.1.4 NAME 'SIPIdentityAddress' )
attributetypes: (0.0.8.350.1.1.6.1.5 NAME 'SIPIdentityPassword' )
attributetypes: (0.0.8.350.1.1.6.1.6 NAME 'SIPIdentityUserName' )
attributetypes: (0.0.8.350.1.1.6.1.7 NAME 'SIPIdentityServiceLevel')
-
#
# re-add the attributes -- in case there is a change of definition
#
#
add: attributetypes
attributetypes: (0.0.8.350.1.1.6.1.1
     NAME 'SIPIdentitySIPURI'
     DESC 'Universal Resource Indicator of the SIP UA'
     EQUALITY caseExactMatch
     SUBSTR caseExactSubstringsMatch
     SYNTAX 1.3.6.1.4.1.1466.115.121.1.15 )

attributetypes: (0.0.8.350.1.1.6.1.2
     NAME 'SIPIdentityRegistrarAddress'
     DESC 'specifies the location of the registrar'
     EQUALITY caseIgnoreIA5Match
     SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )
attributetypes: (0.0.8.350.1.1.6.1.3
     NAME 'SIPIdentityProxyAddress'
     DESC 'Specifies the location of the SIP Proxy'
     EQUALITY caseIgnoreIA5Match
     SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )
attributetypes: (0.0.8.350.1.1.6.1.4
     NAME 'SIPIdentityAddress'
     DESC 'IP address of the UA'
     EQUALITY caseIgnoreIA5Match
     SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )
attributetypes: (0.0.8.350.1.1.6.1.5
     NAME 'SIPIdentityPassword'
     DESC 'The user agent SIP password '
     EQUALITY octetStringMatch
     SYNTAX 1.3.6.1.4.1.1466.115.121.1.40 )
attributetypes: (0.0.8.350.1.1.6.1.6
     NAME 'SIPIdentityUserName'
     DESC 'The user agent user name.'
     EQUALITY caseIgnoreMatch
     SUBSTR caseIgnoreSubstringsMatch
     SYNTAX 1.3.6.1.4.1.1466.115.121.1.15 )
attributetypes: (0.0.8.350.1.1.6.1.7
     NAME 'SIPIdentityServiceLevel'
     DESC 'To define services that a user can belong to.'
     EQUALITY caseIgnoreIA5Match
     SUBSTR caseIgnoreIA5SubstringsMatch
     SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )
-
# Object Class Definitions
#
#    The following object class is defined in this Recommendation:
#
#        SIPIdentity
#
# SIPIdentity
#
#
delete: objectclasses
objectclasses: (0.0.8.350.1.1.6.2.1 NAME 'SIPIdentity' )
-
add: objectclasses
objectclasses: (0.0.8.350.1.1.6.2.1
     NAME 'SIPIdentity'
     DESC 'SIPIdentity object'
     SUP top AUXILIARY
     MAY ( SIPIdentitySIPURI $ SIPIdentityRegistrarAddress $
          SIPIdentityProxyAddress $ SIPIdentityAddress $
          SIPIdentityPassword $ SIPIdentityUserName $
          SIPIdentityServiceLevel $ userSMIMECertificate )
     )
-
#
# end of LDIF
#

5.4. H.350.4 Annex A Indexing profile

Indexing of attributes is an implementation-specific activity and depends upon the desired application. Non-indexed attributes can result in search times sufficiently long to render some applications unusable. Notably, user and alias lookup should be fast. The Annex A Indexing Profile describes an indexing configuration for SIPIdentity directories that will be optimized for use in directory of directories applications. Use of this profile is optional.

SIPIdentitySIPURI:

                      equality

SIPIdentityRegistrarAddress:

                                no recommendation

SIPIdentityProxyAddress:

no recommendation

SIPIdentityAddress:

                       equality

SIPIdentityUserName:

                        equality

SIPIdentityPassword:

                        no recommendation

SIPIdentityServiceLevel:

                            equality

6. Acknowledgments

We are grateful to numerous colleagues for reaching across multiple boundaries of standards bodies, research networks, academia and private industry in order to produce an architecture that works toward integrating multimedia conferencing deployments. In particular, standards from both IETF and ITU-T were drawn from extensively, and the architecture is meant to serve all communities.

This work developed out of the Video Conferencing Middleware (VidMid-VC) working group, a joint effort of Internet2 (www.internet2.edu) and the Video Development Initiative (www.vide.net). The architecture was developed in response to deployment challenges discovered in the ViDeNet (https//:videnet.unc.edu) academic test bed providing video and voice over IP infrastructure across research networks internationally.

This work was supported in part by a grant from the United States National Science Foundation contract number ANI-0222710.

7. Security Considerations

This section is not present in the ITU-T standard, but gives information for the IETF community. Its content has the consensus of the ITU-T Study Group 16.

H.350 does not alter the security architectures of any particular protocol. However, it does offer a standardized place to store authentication credentials where appropriate. It should be noted that both H.323 and SIP support shared secret authentication (H.235 Annex D and HTTP Digest, respectively). These approaches require that the call server have access to the password. Thus, if the call server or H.350 directory is compromised, passwords also may become compromised. These weaknesses may be due to weaknesses in the systems (H.350 directory or call servers) and their operation rather than in H.350 per se.

The userSMIMECertificate attribute is defined in RFC 2798 (section 2.8) as a part of inetOrgPerson. The SIP user agent's X.509 certificate can be stored in this attribute. When the certificate is present, it can be employed with S/MIME to provide authentication, integrity, and confidentiality as specified in RFC 3261 [5].

It is strongly encouraged that call servers and an H.350 directory mutually authenticate each other before sharing information. Further, it is strongly encouraged that communications between H.350 directories and call servers or endpoints happen over secure communication channels such as SSL or TLS.

Finally, access control lists on LDAP servers are a matter of policy and are not a part of the standard. System administrators are advised to use common sense when setting access control on H.350 attributes. For example, password attributes should only be accessible by the authenticated user, while address attributes might be publicly available.

8. References

8.1. Normative References

   [1]  Hodges, J. and R. Morgan, "Lightweight Directory Access Protocol
        (v3): Technical Specification", RFC 3377, September 2002.
   
   [2]  ITU-T Recommendation H.350, "Directory services architecture for
        multimedia conferencing", 2003.
   
   [3]  ITU-T Recommendation H.350.4, "Directory services architecture
        for SIP", 2003.
   
   [4]  Franks, J., Hallam-Baker P., Hostetler, J., Lawrence, S., Leach,
        P., Luotonen, A., and L. Stewart, "HTTP Authentication: Basic
        and Digest Access Authentication", RFC 2617, June 1999.
   
   [5]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,
        Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP:
        Session Initiation Protocol", RFC 3261, June 2002.
   
   [6]  Rosenberg, J. and H. Schulzrinne, "Session Initiation Protocol
        (SIP): Locating SIP Servers", RFC 3263, June 2002.
   
   [7]  Smith, M., "Definition of the inetOrgPerson LDAP Object Class",
        RFC 2798, April 2000.

8.2. Informative References

   [8]  ITU-T Recommendation H.350.1, "Directory services architecture
        for H.323", 2003.
   
   [9]  ITU-T Recommendation H.350.2, "Directory services architecture
        for H.235", 2003.
   
   [10] ITU-T Recommendation H.350.3, "Directory services architecture
        for H.320", 2003.
   
   [11] ITU-T Recommendation H.350.5, "Directory services architecture
        for Non-Standard Protocols", 2003.
   
   [12] ITU-T Recommendation H.350.6, "Directory services architecture
        for Call Forwarding and Preferences", 2004.
   
   [13] Howes T. and M. Smith, "Understanding And Deploying LDAP
        Directory Services", New Riders Publishing, ISBN: 1578700701,
        1999.
   
   [14] Howes T. and M. Smith, "LDAP Programming Directory-Enabled
        Applications with Lightweight Directory Access Protocol", New
        Riders Publishing, ISBN: 1578700000, 1997.

9. Relationship to Other Specifications

This specification is an RFC publication of an ITU-T publication [4], without textual changes within the standard itself (Section 4). The present section appears in the RFC publication only. In order for this specification to be implemented properly, a number of standards pertaining to LDAP [1], [7], H.350 [2],[3], and SIP [4], [5], [6], [7], need to be implemented in whole or in part by the implementor.

   For some background information on the ITU and IETF directory service
   protocols, reading [8], [9], [10], [11], and [12] is valuable, and
   [13] and [14] are recommended books.

10. Authors' Addresses

Tyler Johnson
Editor, H.350
University of North Carolina
Chapel Hill, NC 27599

   Phone: +1.919.843.7004
   EMail: Tyler_Johnson@unc.edu
   
   Sakae Okubo
   Rapporteur for Q.4/16, ITU-T SG16
   Waseda University
   YRP Ichibankan, 3-4 Hikarinooka
   Yokosuka-shi, 239-0847 Japan
   
   Phone: +81 46 847 5406
   EMail: sokubo@waseda.jp

Simao Ferraz de Campos Neto
Counsellor, ITU-T SG 16
International Telecommunication Union
Place des Nations
Geneva CH1211 - Switzerland

   Phone: +41-22-730-6805
   EMail: simao.campos@itu.int

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