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Network Working Group L. Daigle Request for Comments: 2970 T. Eklof Category: Informational October 2000

Architecture for Integrated Directory Services - Result from TISDAG

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

 Copyright (C) The Internet Society (2000).  All Rights Reserved.


 A single, unified, global whitepages directory service remains
 elusive.  Nonetheless, there is increasing call for participation of
 widely-dispersed directory servers (i.e., across multiple
 organizations) in large-scale directory services.  These services
 range from national whitepages services, to multi-national indexes of
 WWW resources, and beyond.  Drawing from experiences with the TISDAG
 (Technical Infrastructure for Swedish Directory Access Gateways)
 ([TISDAG]) project, this document outlines an approach to providing
 the necessary infrastructure for integrating such widely-scattered
 servers into a single service, rather than attempting to mandate a
 single protocol and schema set for all participating servers to use.

1. Introduction

 The TISDAG project addressed the issue of providing centralized
 access to distributed information for whitepages information on a
 national scale.  The specification of the eventual system is
 presented in [TISDAG], and [DAGEXP] outlines some of the practical
 experience already gained in implementing a system of this scale and
 nature.  [DAG-Mesh] considers the issues and possibilities of
 networking multiple DAG services.  Following on from those, this
 document attempts to describe some of the architectural underpinnings
 of the system, and propose directions in which the approach can be
 generalized, within the bounds of applicability.

Daigle & Eklof Informational [Page 1] RFC 2970 Architecture for IDS - Result from TISDAG October 2000

 The proposed architecture inserts a coordinated set of modules
 between the client access software and participating servers.  While
 the client software interacts with the service at a single entry
 point, the remaining modules are called upon (behind the scenes) to
 provide the necessary application support.  This may come in the form
 of modules that provide query proxying, schema translation, lookups,
 referrals, security infrastructure, etc.
 Part of this architecture is an "internal protocol" -- called the
 "DAG/IP" in the TISDAG project.  This document also outlines the
 perceived requirements for this protocol in the extended DAG.

2.0 Some terminology

 Terms used in this document are compliant with those set out in
 [ALVE]. For the purposes of this document, important distinctions and
 relationships are defined between applications, services, servers and
 systems.  These are defined as follows:
 Application:  this is meant in the general sense, as a solution to a
   particular (set of) user need(s).  That is, the definition is not
   tied to a particular piece of software (as in "application
   The definition of an application includes the type(s) of
   information to be exchanged, expected behavior, etc.  Thus, a
   whitepages (search) application may expect to receive a name as
   input to a query engine, and will return all information associated
   with the name.  By contrast, a specific security application might
   use the same input name to verify access controls.
 Service:  an operational system providing (controlled) access to
   fulfill a particular application's needs.
   One service may be changed by configuring location, access
   controls, etc.  Changing application means changing the service.
 Server:  a single component offering access through a dedicated
   protocol, without regard to a specific service (or services) it may
   be supporting in a given configuration. Typically programmed for a
   particular application.
 System:  a set of components with established interconnections.
   Thus, a service can be split between several servers.  A collection
   of services (independently, or interrelated through specified
   agreements) act as an implementation of an application.  A system
   is composed of one or more servers and services.

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   A "system architecture" identifies specific software components,
   their behavior, communication channels and messages needed to
   fulfill a particular service's needs.  The TISDAG specification
   [TISDAG] includes just such a description, defining a software
   system that will meet the needs of a national whitepages directory
   service.  Here, we outline some of the general principles which
   lead to that specific system architecture and discuss ways in which
   the principles can be applied in other contexts.
   Looking at this bigger picture, we present a "service
   architecture", or a framework for assembling components into
   systems that meet the needs of a wider variety of services.  This
   is not a question of developing one or more new protocols for
   services, but rather to examine a useful framework of
   interoperating components.  The goal is to reduce the overall
   number of (specialized) protocols that are developed requiring
   incorporation of some very general concepts that are common to all

3.0 TISDAG – a first implementation, and some generalizations

 The Swedish TISDAG project (described in detail in [TISDAG], with
 some experiences reported in [DAGEXP]) was designed to fulfill the
 requirements of a particular national directory service.   The
 experience of developing component-based system for providing a
 directory service through a uniform interface (client access point)
 provided valuable insight into the possibilities of extending the
 system architecture so that services with different base requirements
 can benefit from many of the same advantages.

3.1 Deconstructing the TISDAG architecture

 In retrospect, we can describe the TISDAG system architecture in
 terms of 3 key requirements and 4 basic design principles:
    R1. The service had to function with (several) existing client and
        server software for the white pages application.
    R2. It had to be possible to extend the service to accommodate new
        client and server protocols if and when they became relevant.
    R3. The service had to be easily reconfigurable -- to accommodate
        more machines (load-sharing), etc.
    D1. As a design principle, it was important to consider the
        possibility that queries and information templates (schema)
        other than the originally-defined set might eventually be

Daigle & Eklof Informational [Page 3] RFC 2970 Architecture for IDS - Result from TISDAG October 2000

    D2. As the architecture was already modular and geared towards
        extensibility, it seemed important to keep in mind that the
        same (or a similar) system could be applied to other (non-
        white pages) applications.
    D3. There is an "inside" and an "outside" to the service --
        distinguishing between components that are accessible to the
        world at large and those that are open only to other
        components of the system.
    D4. Internally, there is a single protocol framework for all
        communications -- this facilitates service support functions
        (e.g., security of transmission), ensures distributability,
        and provides the base mechanism for allowing/ascertaining
        interoperability of components.
 The resulting system architecture featured modular component (types)
 to fulfill a small number of functional roles, interconnected by a
 generic query-response language.  The functional roles were defined
    CAPs -- "client access points" -- responsible for accepting and
    responding to incoming requests through programmed and configured
    behavior -- to translate the incoming query into some set of DAG-
    internal actions (queries) and dealing with the responses,
    filtering and recombining them in such a way as to fulfill the
    client request within the scope of the service.  In the TISDAG
    system, all CAPs are responsible for handling whitepages queries,
    but the CAPs are distinguished by the application protocol in
    which they will receive queries (e.g., LDAPv2, LDAPv3, HTTP, etc).
    To the client software, the TISDAG system appears as a server of
    that particular protocol.  In the more general case, CAPs may be
    configured to handle different aspects of a service (e.g.,
    authenticated vs.  non-authenticated access).  While the TISDAG
    CAPs all had a simple control structure, the more general case
    would also see CAPs drawing on different subsets of DAG (internal)
    servers in order to handle different query types.  (See the
    "Operator Service" example, in section 5.2 below).
    SAPs -- "service access points" -- responsible for proxying DAG-
    internal queries to specified services.  These are resources drawn
    upon by other components within the system.  Through programmed
    and configured behavior, they translate queries in the internal
    protocol into actions against (typically external) servers, taking
    care of any necessary overhead or differences in interaction
    style, and converting the responses back into the internal
    protocol.  In the TISDAG system, all SAPs are responsible for
    handling whitepages queries, but they are distinguished by the

Daigle & Eklof Informational [Page 4] RFC 2970 Architecture for IDS - Result from TISDAG October 2000

    application protocol in which they will access remote services.
    Further distinctions could be made based on the (remote service's)
    schema mappings they handle, and other service differentiators.
    Internal Servers respond to queries in the internal protocol and
    provide specific types of information.  In the TISDAG system,
    there is one internal server which provides referral information
    in response to queries.
 Note that all these components are defined by the functional roles
 they play in the system, not the particular protocols they handle, or
 even the aspect of the service they are meant to support.  That is, a
 client access point is responsible for handling client traffic,
 whether its for searching, establishing security credentials, or some
 other task.

3.2 Some generalizations

 The Requirements and Design principles outlined above are not
 particular to a national whitepages service.  They are equally
 applicable in any application based on a query-response model, in
 services where multiple protocols need to be supported, and/or when
 the service requires specialized behavior "behind the scenes".  In
 the TISDAG project, this last was inherent in the way the service
 first looks for referrals, then makes queries as appropriate.  For
 protocols that don't handle the referral concept natively, the TISDAG
 system proxies the queries.
 Because of its particular application to query-response situations,
 the term "Directory Access Gateway", or "DAG" still fits as a label
 for this type of system architecture.
 Internet applications are evolving, and require more sophisticated
 features (e.g., security mechanisms, accounting mechanisms,
 integration of historical session data).  Continuing to develop a
 dedicated protocol per application type results in encumbered and
 unwieldy protocols, as each must implement coverage of all of these
 common aspects.  But creating a single multi-application protocol
 seems unlikely at best.  The implicit proposal here is that, rather
 than overloading protocols to support multiple aspects of a service,
 those aspects can be managed by breaking the service into multiple
 supporting components to carry out the specialized tasks of
 authentication, etc.

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3.3 A Word on DAG/IP

 In the TISDAG project, the choice was made to use a single "internal
 protocol" (DAG/IP).  The particular protocol used is not relevant to
 the architecture, but the principle is important.  By selecting a
 single query-response transaction protocol, the needs of the
 particular application could be mapped onto it in terms of queries
 and data particular to the application.  This makes the internal
 communications more flexible for configuration to other environments
 (services, applications).
 It is common today to select an existing, widely deployed protocol
 for transferring commands and data between client and server -- e.g.,
 HTTP.  However, apart from any issues of the appropriateness (or
 inappropriateness) of extending HTTP to this use, the work would have
 remained to define all the transaction types and data types over that
 protocol -- the specification of the interaction semantics and

3.4 Perceived benefits

 Apart from the potential to divide and conquer service aspects, as
 described above, this approach has many perceived benefits:
  1. For multi-protocol environments, it requires on the order of

N+M inter-protocol mappings, not NxM.

  1. distribution of development
  2. distribution of operation
  3. eventual possibilities of hooking together different

systems (of different backgrounds)

  1. separation of
    1. architectural principles
    2. implementation to a specific application
    3. configuration for a given service
 It is not the goal to say that a standardized system architecture can
 be made so that single components can be built for all possible
 applications.  However, this approach in general permits the
 decoupling of access protocols from specific applications, and
 facilitates the integration of necessary infrastructure independently
 of access protocol (e.g., referrals, security, lookup services,
 distribution etc).

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4.0 Proposed service architecture

 Pictorially, the DAG architecture is as follows:
   "a" |         |                +--------+       |
 <----->  CAP a  |                | SAP A  |       |
       |         |                |        |       |
       |---------+                +-+------+---+   |
       |                            |(Internal)|   |
       |           "DAG/IP"         | Server i |   |
       |                            +----------+   |
       |                                           |
       |                                           |
       |                          +--------+       | "B"
       |                          | SAP B  <-------------->
       |                          |        |       |
       |                          +--------+       |
       |                                           |
 Note that the bounding box is conceptual -- all components may or may
 not reside on one server, or a set of servers governed by the
 provider of the service.
 As we saw in the TISDAG project, the provider of this DAG-based
 service may be only loosely affiliated with the remote services that
 are used (Whitepages Directory Service Providers (WDSPs) in this

4.1 Using the architecture

 Building a service on this architecture requires:
 Service implementation:
    1. definition of the overall application to be supported by the
       system -- whitepages, web resource indexing, medical
    2. requirements
    3. expected behavior
 System architecture:
    1. nature of deployment -- distributed, security requirements,
    2. identification of necessary CAPs -- in terms of access
       protocols to be supported, different service levels to be
       provided (e.g., secure and unsecure connections)

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    3. identification of necessary services -- e.g., proxying to
       remote information search services, lookup services, "AAA[A]"
       (Authentication, Authorization, Accounting, [and Access])
       servers, etc
    4. definition of the transaction process for the service:  insofar
       as the CAPs represent the service to client software, CAP
       modules manage the necessary transactions with other service
 Data architecture:
    1. selection of schemas to be used (in each protocol)
    2. definition of schema and protocol mappings -- into and out of
       some DAG/IP representation

5.0 Illustrations

5.1 Existing TISDAG Project

 Consider the TISDAG project in the light of the above definitions.
 Service implementation:
    1. A national-scale subset of Whitepages lookups, with specific
       query types supported: only certain schema attributes were
       permitted in queries, and the expected behavior was limited in
    2. Requirements: the service had to support multiple query
       protocols (from clients and for servers), and be capable of
       searching the entire space of data without centralizing the
       storage of records.
    3. Given a query of accepted type, provide referrals to whitepages
       servers that might have information to fulfill the query; if
       necessary, proxy the referrals (chain) to retrieve the
       information for the client.
 System architecture:
    1. distributable components
    2. publicly accessible CAPs in HTTP, SMTP, Whois++, LDAPv2, and
    3. referral proxies to Whois++, LDAPv2 and LDAPv3 WDSPs, as well
       as a referral query service
    4. the basic transaction process, uniform across all CAPs, is:
            - query the RI for relevant referrals
            - where necessary, chain referrals through SAPs of
              appropriate protocol return, in the native protocol, all
              remaining referrals and data

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 Data architecture:  see the spec.
 In the TISDAG project, the above diagram could be mapped as follows:
    CAP a           LDAPv2 CAP
    SAP A           the Referral Index (RI) interface
    Server i        the Referral Index (RI)
    SAP B           LDAPv3 SAP
 Note that, in the TISDAG project specification, the designation SAP
 referred exclusively to proxy components designed to deal with
 external servers.  The Referral Index was considered an entity in its
 own right.  However, generalizing the concepts of the TISDAG
 experience lead to the proposal of regarding all DAG/IP-supporting
 service components as SAPs, each designed to carry out a particular
 type of service functionality, and whether the server is managed
 internally to the DAG system or not is immaterial.

5.2 Operator service

 Consider the case of "number portability" -- wherein it is necessary
 to determine the current service provider of a specific phone number.
 The basic assumption is that phone numbers are assigned to be
 globally unique, but are not in any way tied to a specific service
 provider.  Therefore, it is necessary to determine the current
 service provider for the given number before being able to retrieve
 current information.  For the sake of our illustration, let us assume
 that the management of numbers is two-tiered -- suppose the system
 stores (internally) the mapping between these random digit strings
 and the country in which each was originally activated, but relies on
 external (country-specific) services to manage the updated
 information about which service provider currently manages a given
 number.  Then, the service data need only be updated when new numbers
 are assigned, or national services change their access points.
 We can look at a grossly-simplified version of the problem as an
 illustration of some of the concepts proposed in this service
 architecture.  We couple it with the "name search" facet of the
 TISDAG example, to underscore that a single service ("operator") may
 in fact be supported by several disjunct underlying activities.
 Service implementation:
    1. Retrieving service information for a particular (unstructured)
       phone number digit sequence, or searching for numbers
       associated with a particular name (or fragment thereof).
    2. Requirements:  support IP-telephony through HTTP-based
       requests, wireless device requests through WAP [WAP].

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    3. Expected behavior:  given a name (fragment), return a list of
       names and numbers to match the fragment; given a phone number,
       return appropriately-structured information re. the current
       service mapping for that number.
 System architecture:
    1. Publicly accessible through CAPs; components widely
    2. Need one CAP for HTTP, one for WAP.
    3. Support services include:  an internal service for lookup of
       number strings (to identify nation of origin of the number), a
       proxy to access national services for registration of numbers
       and service providers, and a proxy for remote service provider
       for retrieval of detailed information regarding numbers.  For
       the name searching, we also need a referral index over the
       names, and a proxy to whatever remote servers are managing the
       whitepages directories.
    4. Now, 2 different types of transaction are possible:  search for
       name, or look-up a number.  In the name search case, the CAP
       receives a name or name fragment, looks it up in the internal
       referral index, and finds associated numbers through external
       whitepages services (WDSPs).  To look-up a number, the CAP
       first uses the internal look-up service to determine the
       country of origin of the number, and then uses a SAP to access
       that nation's number-service provider directory, and finally
       uses a different SAP to access the current service provider to
       determine the information required to make the call.
 Data architecture:
      [Out of scope for the purposes of this illustration]
      Note that some elements of the system architecture are
      deliberately vague.  Per the requirements, no structure is
      expected in the number string, and therefore the lookup server
      must maintain an index of number-to-country mappings and relies
      on an external number-to-service mapping service (in each
      country).  However, were there any structure to the numbers, the
      lookup server could make use of that structure in the indexing,
      or in distribution of the index itself.  This would have no
      effect on the CAPs, which have no inherent reliance on how the
      lookup server performs its task.

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      Pictorially, the example can be rendered as follows:
   "a" |         |                +--------+       |
 <----->  CAP a  |                | SAP A  |       |
       |         |                |        |       |
       |---------+                +-+------+---+   |
       |                            |(Internal)|   |
       |           "DAG/IP"         | Server i |   |
       |                            +----------+   |
       |                                           |
       |                          +--------+       | "B"
       |                          | SAP B  <-------------->
       |                          |        |       |
       |                          +--------+       |
       |                                           |
       |                          +--------+       | "C"
       |---------+                | SAP C  <-------------->
   "b" |         |                |        |       |
 <----->  CAP b  |                +--------+       |
       |         |                                 |
       |---------+                +--------+       |
       |                          | SAP D  |       |
       |                          |        |       |
       |                          +-+------+---+   |
       |                            |(Internal)|   |
       |                            | Server j |   |
       |                            +----------+   |
       |                                           |
       |                          +--------+       | "E"
       |                          | SAP E  <-------------->
       |                          |        |       |
       |                          +--------+       |
    CAP a           HTTP CAP
    CAP b           WAP CAP
    SAP A           the number-nation lookup interface
    Server i        number-nation lookup server (what country)
    SAP B           nation-service lookup SAP (what service provider)
    SAP C           service-number information lookup SAP (current
                    service details)
    SAP D           referral index interface
    Server j        referral index service
    SAP E           proxy for chaining queries to remote WDSPs

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5.3 Medical application

 The service architecture is useful for applications outside the scope
 of "telecoms".  In another hypothetical illustration, consider the
 case of medical information -- records about patients that may be
 created and stored at a variety of institutions which they visit.  It
 is not unusual to need to access all information concerning a
 patient, whether or not the person can recollect (or communicate)
 conditions that were treated, procedures that were performed, or
 medical institutions visited.  The data may include everything from
 prescriptions, to X-rays and other images, to incident reports and
 other elements of medical history, etc.  Typically, the information
 is stored where it is collected (or by an agency authorized by that
 institution) -- not in a central repository.  Any service that looks
 to provide complete answers to queries must deal with these
 realities, and clearly must function with a strong security model.
 Service implementation:
    1. Retrieving all medical information for a particular person.
    2. Requirements:  must retrieve, or at least locate, all
       available information, regardless of its storage location;
       cannot require central repository of information; must
       implement authorization and access controls.  Must
       support a proprietary protocol for secure connections
       within hospitals, wireless access for personnel in
       emergency vehicles (not considered secure access).
    3. Expected behavior:  given a patient's national ID, and
       authorized access by medical personnel in secure locations,
       determine what kinds of records are available, and where;
       given a request for a specific type of record, retrieve
       the record.  Given a patient's national ID, and authorized
       access from a wireless device, provide information re.
       any known medical flags (e.g., medicine allergies,
       conditions, etc).
 System architecture:
    1. Only 2 CAP types are needed, but instances of these will
       be established at major medical institutions.
    2. Need one CAP to support the proprietary protocol, one
       to support wireless access.
    3. Support services include:  an internal server to support
       security authentication and access control determination;
       an internal server to act as referral index for finding
       information pertinent to a particular patient, and one
       or more proxies for accessing remote data storage servers.
    4. The basic transaction requires that the first step be
       to authenticate the end-user and determine access privileges.
       In the case of wireless access, this last will not involve

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       a specific lookup, but rather will be set to allow the
       user to see the list of publicized medical conditions.
       Depending on the query type, the next step will be to
       contact the referral index to determine what records
       exist, and then track down information at the remote sources.
 Data architecture:
         [Out of scope for the purposes of this illustration]
 Pictorially, the example can be rendered as follows:
   "a" |         |                +--------+       |
 <----->  CAP a  |                | SAP A  |       |
       |         |                |        |       |
       |---------+                +-+------+---+   |
       |                            |(Internal)|   |
       |           "DAG/IP"         | Server i |   |
       |                            +----------+   |
       |                                           |
       |                                           |
       |                          +--------+       | "B"
       |---------+                | SAP B  <-------------->
   "b" |         |                |        |       |
 <----->  CAP b  |                +--------+       |
       |         |                                 |
       |---------+                +--------+       |
       |                          | SAP C  |       |
       |                          |        |       |
       |                          +-+------+---+   |
       |                            |(Internal)|   |
       |                            | Server j |   |
       |                            +----------+   |
    CAP a           CAP for proprietary protocol, secure clients
    CAP b           WAP CAP, for roaming access
    SAP A           authentication and ACL lookup interface
    Server i        authentication and ACL lookup server
    SAP B           remote service SAP -- probably LDAPv3
    SAP C           Referral Index interface
    Server j        Referral Index

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6. Requirements for the future DAG/IP

 The role of the DAG/IP is less as a query protocol, and more as a
 framework or structure for carrying basic query-response transactions
 of different (configurable) types.
 Whatever the syntax or grammar, the basic requirements for the DAG/IP
 include that it be:
  1. lightweight; CAPs, SAPs should be able to be quite small
  2. flexible enough to carry queries of different paradigms, results

of different types

  1. able to support authentication, authorization, accounting and

audit mechanisms – not necessarily native to the protocol

  1. able to support encryption and end-to-end security within the

DAG system

  1. sophisticated enough to allow negotiation of capabilities –

querying & identifying application type supported (e.g.,

      whitepages vs. service location vs. URN resolution), query types
      supported, results types supported
    This also means:
 Better support for query-passing/other query semantics (need to
 balance that against the fact that you don't want DAG-CAPs/SAPs to
 have to know a multiplicity of semantic possibilities.
 Security infrastructure -- ability to establish security credentials,
 maintain a secure transaction, and propagate the security information
 forward in the transaction (don't want to reinvent the wheel, just
 want to be able to use it!).
 Ability to do lookups, instead of searches -- might mean connecting
 to different services than the RI and/or presenting things in a
 slightly different light -- e.g., lookup <blat> in the <foo> space,
 as opposed to search for all things concerning <blat>.
 Ability to access other services -- e.g., Norwegian Directory of
 Directories [NDD] -- beyond just for specific characteristics of the
 service (e.g., security).
 In short, the model that seems to stand out from these requirements
 one of a protocol framework that looks after establishing secure and
 authenticated (authorized, accountable, auditable...) connections,
 with transaction negotiation facilities.  Within that framework, it
 must be possible to identify transaction types, provide suitable
 input information (negotiation?) for those transactions, and accept
 transaction result objects back.

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7. Revisiting TISDAG – for the future

 In the light of the above proposals, we can revisit the way the
 TISDAG CAPs would be defined.
 The whitepages-application service known as TISDAG could have SAPs
 that supported 2 types of query, and 2 types of result sets:
         query types:
                 . token-based
                 . phrase-based
         result types:
                 . result data
                 . referrals
 The Whois++ CAP would be configured to contact LDAPv2 and LDAPv3 SAPs
 because they are identified as providing that kind of service (i.e.,
 if referral protocol == LDAPv2 connect to a particular service).  The
 query paradigm will be phrase-oriented -- NOT because the Whois++ CAP
 understands LDAP, but because that is one of the defined query types.

8. Applicability Limitations

 As it stands, this type of service architecture is limited to query-
 response type transactions.  This does account for a broad range of
 applications and services, although it would be interesting to
 consider broadening the concept to make it applicable to tunneling
 other protocols (e.g., to connect a call through a SAP, in the number
 portability example above).

9. Security Considerations

 This document takes a high-level perspective on service architecture,
 and as such it neither introduces nor addresses security concerns at
 an implementation level.
 A distributed service built following this approach must address
 issues of authentication of users, authorization for access to
 material/components of the system, and encryption of links between
 them, as befits the nature of the information and service provided.

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10. Acknowledgements

 In discussing this perspective on the evolution of DAG/IP, it seemed
 to us that the requirements for DAG/IP are falling into line with the
 proposed text-based directory access protocol that has variously been
 discussed.  Whether it survives in a recognizable form or not :-)
 some of the above has been drawn from discussions of that protocol
 with Michael Mealling and Patrik Faltstrom.
 The work described in this document was carried out as part of an on-
 going project of Ericsson.  For further information regarding that
 project, contact:
    Bjorn Larsson

11. Authors' Addresses

 Leslie L. Daigle
 Thinking Cat Enterprises
 Thommy Eklof
 Hotsip AB

12. References

 Request For Comments (RFC) and Internet Draft documents are available
 from numerous mirror sites.
 [ALVE]     Alvestrand, H., "Definitions for Talking about
            Directories", Work in Progress.
 [TISDAG]   Daigle, L. and R. Hedberg "Technical Infrastructure for
            Swedish Directory Access Gateways (TISDAG)", RFC 2967,
            October 2000.
 [DAGEXP]   Eklof, T. and L. Daigle, "Wide Area Directory Deployment
            Experiences", RFC 2969, September 2000.
 [DAG-Mesh] Daigle, L. and T. Eklof, "Networking Multiple DAG servers:
            Meshes", RFC 2968, September 2000.

Daigle & Eklof Informational [Page 16] RFC 2970 Architecture for IDS - Result from TISDAG October 2000

 [NDD]      Hedberg, R. and H. Alvestrand, "Technical Specification,
            The Norwegian Directory of Directories (NDD)", Work in
 [WAP]      The Wireless Application Protocol,

Daigle & Eklof Informational [Page 17] RFC 2970 Architecture for IDS - Result from TISDAG October 2000

13. Full Copyright Statement

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 This document and the information contained herein is provided on an


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Daigle & Eklof Informational [Page 18]

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