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Network Working Group                                          L. DaigleRequest for Comments: 2970                                      T. EklofCategory: Informational                                     October 2000Architecture for Integrated Directory Services - Result from TISDAGStatus 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.Abstract   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     program").     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.Daigle & Eklof               Informational                      [Page 2]

RFC 2970       Architecture for IDS - Result from TISDAG    October 2000     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     protocols.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          supported.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   as:      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, insection 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 theDaigle & 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.Daigle & Eklof               Informational                      [Page 5]

RFC 2970       Architecture for IDS - Result from TISDAG    October 20003.3 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   syntax.3.4 Perceived benefits   Apart from the potential to divide and conquer service aspects, as   described above, this approach has many perceived benefits:      - For multi-protocol environments, it requires on the order of        N+M inter-protocol mappings, not NxM.      - distribution of development      - distribution of operation      - eventual possibilities of hooking together different        systems (of different backgrounds)      - separation of              - architectural principles              - implementation to a specific application              - 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).Daigle & Eklof               Informational                      [Page 6]

RFC 2970       Architecture for IDS - Result from TISDAG    October 20004.0 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   case).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         information      2. requirements      3. expected behavior   System architecture:      1. nature of deployment -- distributed, security requirements,         etc.      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)Daigle & Eklof               Informational                      [Page 7]

RFC 2970       Architecture for IDS - Result from TISDAG    October 2000      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         modules   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 representation5.0  Illustrations5.1 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         scope.      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         LDAPv3      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 dataDaigle & Eklof               Informational                      [Page 8]

RFC 2970       Architecture for IDS - Result from TISDAG    October 2000   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].Daigle & Eklof               Informational                      [Page 9]

RFC 2970       Architecture for IDS - Result from TISDAG    October 2000      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         distributed.      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.Daigle & Eklof               Informational                     [Page 10]

RFC 2970       Architecture for IDS - Result from TISDAG    October 2000        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  <-------------->         |                          |        |       |         |                          +--------+       |         +-------------------------------------------+   where      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 WDSPsDaigle & Eklof               Informational                     [Page 11]

RFC 2970       Architecture for IDS - Result from TISDAG    October 20005.3 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 involveDaigle & Eklof               Informational                     [Page 12]

RFC 2970       Architecture for IDS - Result from TISDAG    October 2000         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 |   |         |                            +----------+   |         +-------------------------------------------+   where      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 IndexDaigle & Eklof               Informational                     [Page 13]

RFC 2970       Architecture for IDS - Result from TISDAG    October 20006. 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:      - lightweight; CAPs, SAPs should be able to be quite small      - flexible enough to carry queries of different paradigms, results        of different types      - able to support authentication, authorization, accounting and        audit mechanisms -- not necessarily native to the protocol      - able to support encryption and end-to-end security within the        DAG system      - 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.Daigle & Eklof               Informational                     [Page 14]

RFC 2970       Architecture for IDS - Result from TISDAG    October 20007. 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.Daigle & Eklof               Informational                     [Page 15]

RFC 2970       Architecture for IDS - Result from TISDAG    October 200010. 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      bjorn.x.larsson@era.ericsson.se11. Authors' Addresses   Leslie L. Daigle   Thinking Cat Enterprises   EMail:  leslie@thinkingcat.com   Thommy Eklof   Hotsip AB   EMail: thommy.eklof@hotsip.com12. 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              Progress.   [WAP]      The Wireless Application Protocol,http://www.wapforum.orgDaigle & Eklof               Informational                     [Page 17]

RFC 2970       Architecture for IDS - Result from TISDAG    October 200013.  Full Copyright Statement   Copyright (C) The Internet Society (2000).  All Rights Reserved.   This document and translations of it may be copied and furnished to   others, and derivative works that comment on or otherwise explain it   or assist in its implementation may be prepared, copied, published   and distributed, in whole or in part, without restriction of any   kind, provided that the above copyright notice and this paragraph are   included on all such copies and derivative works.  However, this   document itself may not be modified in any way, such as by removing   the copyright notice or references to the Internet Society or other   Internet organizations, except as needed for the purpose of   developing Internet standards in which case the procedures for   copyrights defined in the Internet Standards process must be   followed, or as required to translate it into languages other than   English.   The limited permissions granted above are perpetual and will not be   revoked by the Internet Society or its successors or assigns.   This document and the information contained herein is provided on an   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Acknowledgement   Funding for the RFC Editor function is currently provided by the   Internet Society.Daigle & Eklof               Informational                     [Page 18]