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Network Working Group                                         K. SollinsRequest for Comments:  1107       M.I.T. Laboratory for Computer Science                                                               July 1989A Plan for Internet Directory Services                           Table of Contents   1. Introduction                                                  1        1.1. The Issues                                             1        1.2. Project Summary                                        3   2. Goals and Requirements for a White Pages Service              6   3. Pre-existing Services                                         9   4. Proposed Approach                                            11        4.1. Stage 1: The Field Test                               12        4.2. Stage 2: Implementation                               17        4.3. Stage 3: Deployment                                   17   5. Conclusion                                                   18Status of this Memo   This memo proposes a program to develop a directory service for the   Internet.  It reports the results of a meeting held in February 1989,   which was convened to review requirements and options for such a   service.  This proposal is offered for comment, and does not   represent a committed research activity of the Internet community.   Activity in this area is anticipated, and comments should be provided   promptly.  Distribution of this memo is unlimited.1. Introduction1.1. The Issues   As part of the planned growth of the Internet (in particular, in   support of the full science research community in the U.S.), an   increasing need is anticipated for various sorts of directory   services.  The increase in the size of the community served by the   Internet and the burgeoning demands for electronic mail lead to the   need for a service to find people's computer mailboxes and other   relevant facts, a so-called "White Pages" service.  At the user level   to date, there have been no such national or international white   pages services in general use.  As part of building the National   Research Network (NRN), it is important that such a service exist,   not only within the NRN community, but also crossing the boundaries   from the NRN to the more global network community.  This will enhance   communication not only among computer scientists, but also amongSollins                                                         [Page 1]

RFC 1107         A Plan for Internet Directory Services        July 1989   scientists and engineers in other fields as well.  Also important and   related is a so-called "Yellow Pages" service, which permits the   location of Internet resources based on their attributes.   A "White Pages" service is one in which one can look up people in   order to learn information about them for finding them.  In its   simplest form, a white pages service provides what the white pages   telephone book provides.  Based on a name, one can find an address   and a telephone number.  In a network environment, there may be many   other kinds of location information, such as electronic mailbox,   electronic calendar, or file server, where one might leave a file for   the recipient.  In addition, the electronic white pages may support a   much more sophisticated set of mechanisms for lookup.  One might   match on a more complex set of attributes than first and last name.   In addition, the searching might span more than one local white pages   service.  There are a number of naming and directory service   specifications and implementations in the field.  They have differing   functionality and mechanisms to address that functionality.   Within the the world of networking today, there are a number of   partial solutions to the directory service problem.  Examples of   these are the Internet Domain Naming Service (DNS), Clearinghouse,   DECnet Network Architecture Naming Service (DNANS), Profile, and   X.500.  The Domain Naming Service provides a directory service most   commonly used for host naming and mail delivery.  Clearinghouse and   DNANS are respectively the Xerox and DEC corporate naming services,   originally for mail delivery, although having other uses as well, in   both cases.  Profile is part of the work of Larry Peterson to explore   descriptive naming in a non-hierarchical structure.   There is a CCITT recommendation X.500 (ISO DIS 9594), which defines a   general directory service.  One of its primary goals is the naming   service needed for message handling (X.400).  While X.500 is still   developing, and would need further evolution to cover all the   requirements of a service for the Internet, it will have an important   impact on the Internet community.  It will form the basis of   commercial products, and it will almost certainly be the directory   service of many parts of the network world, which implies a need to   interoperate at a minimum.  There is some concern that despite the   fact that X.500 is a recognized standard, there are a number of gaps   and limitations of the approach, that in turn will cause it to be   inadequate for the needs of the NRN.   In this context, a meeting was held to review current requirements   and solutions for directory services.  This RFC reports the results   of that meeting, including the possibilities for a program of work in   this area.Sollins                                                         [Page 2]

RFC 1107         A Plan for Internet Directory Services        July 1989   For two days, a group representing academic, commercial, and   government interests in directory services discussed both alternative   candidates for a white pages service and the issues in building any   such service.  The meeting was kept small by inviting only a small   number of representatives of each perspective.  By the conclusion of   the second day, a consensus was reached on how one could achieve a   white pages service in three years.  This is summarized in the next   section.1.2. Project Summary   The consensus of the meeting can be summarized in the following five   points:      1. The standards and implementations are close enough to being         complete that it is reasonable to undertake provision of an NRN         "White Pages" service.      2. Although we are close, an effort is needed to experiment with         different levels of service, to flesh out the standards, and to         develop code.      3. An initial evaluation experiment is needed before making final         detailed plans for a production version of the service.      4. With strong funding and encouragement, a production service is         possible in three years.      5. It is important to act now to provide a coherent solution.         This means both having an impact on the evolving standards         and providing a unified, wide-spread solution before a plethora         of differing solutions appear.   Although it has clearcut drawbacks, X.500 was identified as the most   likely candidate directory service.  The reasons for this are that it   has rich semantics and is becoming the accepted international   standard.  However, there are problems with its incompleteness and   with its strict hierarchy.  Therefore, in order to explore these and   become convinced of its viability, the consensus at the meeting was   to propose field trials, as the project's first stage.  The field   trials would be limited in the user community, perhaps restricted to   computer science departments because of their familiarity with the   problems, and would be based on experimental or new software.  They   would include experiments with at least an X.500 implementation,   Profile, and DNANS.  Each of these services has strong points that   must be considered as part of the evaluation.  They are:Sollins                                                         [Page 3]

RFC 1107         A Plan for Internet Directory Services        July 1989      X.500:  International standard, hierarchy, search rules and              filters for searching attributed based names.      Profile:  Descriptive naming with a richer semantics for                describing search criteria, an arbitrary network                of servers.      DNANS:  Access control, replication, caching, hierarchy.   In summary, the plan would fall into three stages as follows:      - Stage 1:  Field Trials.         There are two aspects to the field trials.  The first is to         explore several different architectures for a white pages         service.  To this end, implementations of X.500, Profile, and         DNANS should be included.  The second aspect of the field         trials is to distinguish issues inherent in the X.500         specification from artifacts of a particular implementation of         it.  Therefore, if possible, two implementations of X.500         should be included.  Only one such implementation, Quipu, was         identified as developed enough to be included in a field trial         at present, but others are under way, and will follow.  This         stage must also include a careful and objective review of the         field trials.      - Stage 2:  Implementation.         This stage will include work on both the service and user         interfaces.  The field trials could result in one of a variety         of conclusions about the service.  These may range from         concluding that one or another of the services suits the needs         of the NRN to proposing a compromise position based on a         combination of shortcomings of any one service and the features         of others to address those shortcomings.  Because X.500 will         become the standard in other domains, an interface to X.500         will be necessary.  Since all of these implementations are         still under development, in order to provide production quality         code, more implementation work will be needed.         Although some work will have been done on the user interfaces,         much more will be needed in this stage to provide a variety of         interfaces.  Much emphasis should be placed on this in Stage 2.      - Stage 3:  Deployment.         Deployment of the full white pages service requires information         gathering in order to fill the directory service, placement ofSollins                                                         [Page 4]

RFC 1107         A Plan for Internet Directory Services        July 1989         servers, distribution of and training for use of client code,         placement and management of services, and delegation of         authority within the service for authority over the contents.         Data collection and some delegation of authority as well as         training for users of the client code would begin during the         field trial.  This stage would begin concurrently with the         other two.  During the second year, detailed planning for         deployment must take place.  This stage would conclude in three         years, at which time widespread deployment would have occurred.   In order to undertake this three stage program effectively, the group   identified the following major projects:      - Further implementation of code for the field trials.         In each case (e.g., Quipu, Profile, and DNANS), programs exist,         although modifications are likely to be necessary.  For         example, each will need to be modified to utilize the common         file format into which the input data about users will be         gathered.      - Design, development and evaluation of user interfaces.      - Design and development of data gathering and management tools.      - Oversight and evaluation of the field trials.         Careful thought and planning must go into the field trials, to         guarantee that we learn what is needed to make an evaluation         and to plan for the white pages service.  The evaluation must         also produce a document that is both a general specification         (assuming no one alternative is chosen wholesale) and profiling         information, in order for later interoperability and         conformance testing.      - Detailed planning and later management of deployment.         This includes delegation of authority over parts of the         namespace and arbitrating the shape of the namespace         (addressing the questions about who gets what sorts of names).         This is in addition to the continued and extended data         collection and management, distributing the data, placing the         code, documentation and user education.      - Standards participation is an important part of the program.         It is critical as X.500 changes during the next 4 year study         period that the United States take a strong stand on anySollins                                                         [Page 5]

RFC 1107         A Plan for Internet Directory Services        July 1989         changes we envision.  It is encumbant on us to utilize         effectively the results of the largest field trials of this         work in the international arena.  The group agreed that this         could take up to one half of one person's time in a year.      - A task force or working group is necessary to provide a forum        for communication and discussion.   It is important to pursue this path now, both to architect a unified   solution before a collection of ad hoc solutions is deployed, and to   provide effective input into the X.500 standards work based on the   field trials.2. Goals and Requirements for a White Pages Service   The requirements of a white pages service are the following:      - Functionality:         The simple form of a white pages service is straightforward;         one should be able to query the service with the name of a         person, and have returned attributes of the person such as         network mail address and phone number.      - Correctness of information:         The information in a white pages service is useless and         untrusted if it is not updated regularly.  A white pages         service will not be used, if the information it provides is out         of date or incorrect.  This will require a set of management         tools.  Data integrity is an especially difficult challenge in         this area, in contrast with information that is syntactically         correct.      - Size:         The science and research community has been estimated at ten         million users.  The number of organizations in the United         States is on the order of ten to one hundred thousand.      - Usage and query rate:         In comparison with the typical telephone book pattern of about         one lookup a week per person, users of electronic mail in the         science and research community will send more electronic mail         messages than they currently make phone calls, leading to an         estimate of ten searches a week per user for electronic as well         as paper mail and telephone information.  This leads to a querySollins                                                         [Page 6]

RFC 1107         A Plan for Internet Directory Services        July 1989         rate of 10**8 queries per week or 170 per second on average,         with much higher peak rates.  The average could probably be         handled by a single server, but not the peak rates and this         would leave little room for growth.  Therefore, a distributed,         multiple server solution is the only one that make sense.      - Response time:         The issue of overall query behavior must be considered         carefully.  The issue arises when queries, in particular         searches, are not limited to tightly constrained sets of         entries.  Since the number of queries generated will be         proportional to the number of users (and the size of the         system), the white pages design must avoid costs per query that         are related to the size of the system.  The consequence,         otherwise, will be quadratic behavior in response time.         The response time of the service must also reflect the expected         usage.  A phone book style query must respond in the waiting         time tolerable to a user, perhaps ten seconds maximum, or one         second desirable.  If the service is incorporated as a         component of a larger service, then the needs of that service         determine the response time.      - Partitioned Authority:         The white pages service under discussion would be used by a         wide variety of organizations, ranging from small and large         companies, to network service providers, to government         agencies.  Many of these would find it unacceptable to delegate         the authority over their namespaces to some other organization.         Therefore, partitioned authority including some access control,         name assignment, and information management must be possible.      - Access Control:         The access control required by the white pages falls into two         categories, read access control, and write or modify access         control.  There are at least two reasons that read access         control must be available.  One is that organizations may         require limiting the access to the actual entries or parts of         them.  This would be comparable to organizations not being         willing to distribute their corporate phone books or personnel         records.  The other reason is that some organizations do not         want to publicize or make public their organizational         structure.  Write and modify access control is necessary         because both individuals and organizations may want to prevent         inadvertent or malicious creation or modification ofSollins                                                         [Page 7]

RFC 1107         A Plan for Internet Directory Services        July 1989         information.  Access control is an issue for both organizations         wanting to retain local control of personnel information and         individuals wanting to control access to private information         about themselves.      - Multiple Transport Protocol Support:         Within the next three years, one cannot expect all the         organizations in the USA to convert to the OSI protocols.  On         the other hand, some will.  It is therefore important that any         white pages service provide interfaces on top of both OSI         protocols and TCP/IP.  There currently exists a partial OSI         suite know as ISODE on top of TCP.  This is being distributed         widely enough that perhaps this should also be supported.   In addition to these requirements, there are a number of features   that would make a white pages service more useful.  These are:      - Additional Functionality:         Descriptive naming with sophisticated searching based on         attributes would support a more flexible human interface than         simple name translation.  Descriptive naming also would support         a general yellow pages style service.         The form of a yellow pages service is less certain.  One         definition of a yellow pages service is a directory that stores         a number of pre-computed inversions of the directory database,         so that entries can be retrieved very efficiently using these         predetermined attributes of the data.  Another definition of a         yellow pages service is one that provides a very powerful set         of search primitives, somewhat in common with a relational         query language, to support retrieval of entries that match         complex attribute conditions.  In other words, one view of a         yellow pages service is that it is constructed to avoid         expensive searches, the other is that it is to facilitate         general searches.      - Accountability:         Accountability is important both for allocation and recovery of         costs.  Vendors may provide commercial directory services,         therefore depending on accounting as part of their successful         commercial ventures.      - Multiple Interfaces:         There should be both human and programming interfaces to theSollins                                                         [Page 8]

RFC 1107         A Plan for Internet Directory Services        July 1989         white pages.  For example, in addition to human lookups, mail         services could effectively use a naming service allow users to         include human oriented names than the current electronic mail         addresses that are required, such as full domain names.      - Multiple Clients:         Several different clients should exist both to provide for a         variety of styles of human usage, and to support selection of         the most commonly used computer environments (e.g., UNIX, VMS,         MSDOS, OS2, MAC/OS).3. Pre-existing Services   This section identifies other naming services that have been proposed   or implemented for naming people.  Implementations of all of these   exist, although some are still only experimental.      Internet Domain Naming Service         The Internet Domain Name Service [6,1] is used today to name         host machines.  It is implemented to address the query rates         and database sizes consistent with looking up hosts as part of         mail delivery.  It provides a hierarchy with delegation of         authority within the hierarchy.  Aliases are also available.         There is no access control, and the service is widely         distributed throughout the Internet.  It supports management of         distribution, replication and caching.  It is operational, and         provides a rich base of practical experience.  It was         originally intended to be extensible to cover naming of people.         It runs on a variety of different operating systems and         utilizes the TCP/IP protocol suite.      The DECnet Network Architecture Naming Service (DNANS)         There is a rather well developed specification [5,3] for a         naming service that is part of the DECnet architecture, which         in turn arose from work at the DEC SRC in Palo Alto.  This         architecture addresses some problems not yet covered by X.500,         such as access control, replication, and caching.  It was         explicitly defined to have great scalability and management         features.  It provides a global hierarchy of names, which are         mapped into properties.  Therefore, operations of searching         based on properties or attributes may be expensive and         difficult.  At present it is only implemented on VMS using the         DNA protocols, but will be moved to UNIX and TCP in the next         year.Sollins                                                         [Page 9]

RFC 1107         A Plan for Internet Directory Services        July 1989      Clearinghouse         This service [7,2] is part of the Xerox network environment.         It operates today as a global service for Xerox.  They have         considerable experience with its operation, including problems         of scale.  Clearinghouse provides a three-level hierarchy of         names that are mapped to sets of properties.  Loose consistency         is provided through slow propagation of updates.  Both this         service and the DEC service mentioned above are to some extent         based on an earlier Xerox service called Grapevine.      Profile         A project at the University of Arizona run by Larry Peterson         [8] has produced a white pages name service called Profile.  It         supports descriptive naming and sophisticated lookup tools.         Profile assumes the existence of some other service such as the         DNS to navigate among Profile servers.  This navigation service         need not restrict the relationship among Profile servers to a         hierarchical organization; Profile supports a non-hierarchical         global structure.  Names in Profile consist of sets of         attributes.  Experimental implementations are in operation         today, and the largest site currently contains about 10,000         entries.  The Profile code has been available for long enough         that it has become stable.  The implementation is UNIX-based         only and uses TCP.      X.500         X.500 is the CCITT recommendation (also ISO/IEC/DIS 9594) [4]         for a directory service.  Because it is a CCITT recommendation,         it evolves in four year study periods, one of which has         recently come to a close.  Thus, X.500 has a stable definition         for the next four years.         In X.500, the set of all objects forms a single hierarchy, with         each object being named relative to its parent and a single         root as the topmost parent.  An object consists of a set of         attributes.  Searching can be done by use of a logical         combination of attribute values, known as a filter.  A subset         of these attributes comprise an object's distinguished name         relative to its parent.  The hierarchy as described in the         CCITT recommendation is geographic at its top level and         organizational within that.  Alternatives can also be defined,         although they are not part of the CCITT or ISO documents.  In         addition, there is no proposed mechanisms for distributing         information about other attribute types or object classes.  As         with the other services, X.500 is a distributed service.  ItSollins                                                        [Page 10]

RFC 1107         A Plan for Internet Directory Services        July 1989         specifies cooperating servers or Directory Server Agents (DSAs)         under local control and management each of which knows about         one or more parts of the hierarchy.  The clients are known as         Directory User Agents (DUAs).  It is defined to run on top of         the OSI protocol stack.  The demonstrations of X.500 in the         context of Internet run on top of the ISODE package, which         provides OSI transport on top of TCP.         X.500 is incomplete in that there are a number of identifiable         areas in which the standard says nothing, but that need to be         specified for a successful implementation.  Some examples of         these are: access control (although authentication is         supported), replication, caching, the database itself (the         shape of the hierarchy), tools to limit the scope and cost of         searching, and database management tools.         There are currently a small number of implementations of X.500         in progress at such locations as University College London (the         Quipu project, on UNIX using ISODE), the University of British         Columbia (UNIX based using their own full OSI suite), MIT         (experimental, Symbolics Lisp Machine based, Lisp using TCP),         The Wollongong Group (offshoot of Quipu), The Retix         Corporation, NIST, and at least several underway in Italy and         Japan.  There are probably others and a number of other         American corporations have discussed building their own.  Each         of these must make its own decision in the areas in which X.500         is silent.  Quipu is probably the most complete implementation         of X.500 to date.  The pilot version has about 20 DUAs in seven         countries with an estimated 20,000 entries total.4. Proposed Approach   The conclusion of this report is that some form of X.500 is the most   likely candidate.  The reasons for this decision are that it has a   rich semantics and will become the international de facto standard.   There are, however, serious problems with its incompleteness and with   its strict hierarchy.  Therefore, in order to explore these and   become convinced of its viability, the attendees at the meeting   agreed on field trials, as a first stage.  Initially, this would   include experiments with at least one X.500 implementation (Quipu),   Profile to explore a non-hierarchical structure and richer   descriptive naming, and DNANS in order to explore some of the   incomplete aspects of X.500 for which DNANS has architected   solutions.   A three-stage plan, with all three stages beginning coincidentally   and as soon as possible, would provide such a service within the NRN.   The first stage should be complete in a year, the second in two, andSollins                                                        [Page 11]

RFC 1107         A Plan for Internet Directory Services        July 1989   the third in three.  Stage 1 would be field trials of three   approaches to naming with an emphasis on distinguishing between the   specification and a particular implementation of X.500, as well.   Stage 2 would be a more complete implementation of a white pages   service base on the conclusions from Stage 1.  Stage 3 would be   widespread deployment of the implementation developed in Stage 2.   The planning for Stage 3 is not outlined here in detail, because that   plan would be part of the proposed work to be done.  If the field   trials were to lead to the conclusion that none of the services is   adequate, the plan for the remainder of the work would need to be   rescheduled.   If the Internet community is to adopt X.500 (or any other standard),   it is necessary to make a number of design and management decisions,   above and beyond the implementation decisions for the DSA.  Since   there are a number of such decisions to be resolved, and some of   these are significant, the group recommended that this planning and   management function should be recognized as a distinct activity.4.1. Stage 1: The Field Test   It was agreed that field trials would be a valuable form in which to   explore the issues of building a white pages service for two reasons.   First, the software is still in early stages of development or   deployment.  Some of it is production code, but still first release;   the rest is part of research projects.  Second, it is important to   learn from experience with a limited and sympathetic community.  The   suggested community was the computer science community, in   particular, computer science departments.  That will not be the case   completely, since the computer science community in general does not   use DECnet.  Therefore, for experiments with the DNANS, the NASA/DOE   community was recommended.  They will be using DNANS in any case, as   they move to DECnet Phase V.   The twofold purpose of the field trials is to explore differing   directory service architectures and to refine the study of X.500   specifically, to distinguish architectural aspects of it from   features of a particular implementation of X.500.  Initially, the   trials would include the Quipu implementation of X.500, Profile, and   the DNANS.  A second implementation of X.500 should be identified and   included as soon as possible.  Part of the emphasis of the field   trials would be on gathering and maintenance of naming information.   To ease this, a single common file format for storage of and access   to the naming information and use of a single set of data management   tools was recommended, although no particular set was identified.   The various directory services would need to be retrofitted to this   file format.  Such consistency in file format would mean that the   services could all be co-resident, sharing files, thus permittingSollins                                                        [Page 12]

RFC 1107         A Plan for Internet Directory Services        July 1989   single locations to participate in several parts of the field trials.   This, in turn, would allow for direct comparisons.   There are a number of issues, which are not addressed in X.500, that   would need to be resolved for a large scale deployment such as a   white pages for the NRN.  In particular, these are: clients of the   service; data collection and maintenance; distribution, replication   and caching of information; access control, accountability, and   information integrity; and support by non-OSI protocols.  Each of the   name services included in the field trials would include decisions in   these areas, albeit different ones.  The field trials will allow for   evaluation of these different mechanisms.   There are two other major issues that must also be addressed:   functionality and size.  Functionality encompasses both the first   point of the nature of the interfaces to the service as well as the   structure of the namespace (e.g., hierarchy).  A discussion of size   must include not only the number of entries handled by the service as   a whole, but how those entries are distributed and the query and   update patterns.   In general, all of these issues are tightly coupled, but are   separated here for the purposes of understanding the field trials and   its potential effectiveness.  They would also be the issues that   would be the basis for the work done in Stage 2 of the project.      - Functionality:         X.500 and DNANS make strong statements about the organization         of the namespace.  In both cases, it is a single, absolute         hierarchy with soft links or aliases and attribute-based naming         useful both in searches of subtrees of the hierarchy and for         storing information about the objects in the hierarchy.  The         searches are based on logical combinations of attribute values.         Quipu implements the naming structure and search functionality         as specified in X.500.  In contrast, Profile, provides a more         general facility that supports any form of relative names, not         just hierarchical, and a small programming language to express         the functions for searching.  By including Profile in the field         trials, these more general facilities can be tested.         X.500 specifies that the service is separated into two parts         for implementation of the service, known as the Directory         Service Agent (DSA), and the client, known as the Directory         User Agent (DUA).  DUAs can be implemented independently of the         implementation of the white pages service.  Quipu, Profile, and         DNANS have taken different approaches to the presentation model         for DUAs, so the three implementations will allow forSollins                                                        [Page 13]

RFC 1107         A Plan for Internet Directory Services        July 1989         additional experience.      - Size:         As discussed earlier, a white pages service must be prepared to         handle a minimum of 10**7 entries, although they may be         distributed, and a query rate of hundreds per second.  It must         also be prepared to handle much higher peak rates.  If the         address lookup that is presently provided by the DNS is also         supported by the white pages service, the query rate will be         much higher.  The designers of the field trials must determine         whether or not such usage will be part of the final service and         therefore must be examined in the field trials.  If so, caching         may be part of the solution.  In addition, the response time         for DUAs must be reasonable for a human sitting at a console.         Furthermore, modifications to the data should occur in         reasonably short periods of time, although this could be         measured in hours.         The field trials must allow for experimentation under such         stressful conditions.  The environment for testing must have         both large and small nodes, as well as both heavy and light         load querying and situations in which reorganization can be         tested.  Such reorganization may be a simple as moving one         piece of the hierarchy to another point and handling naming         conflicts in the new environment.  X.500 does not address this         issue, but it will be needed by the NRN.      - Distribution, replication, and caching:         These are areas in which X.500 has very little to say, but a         great deal of work has been done in other distributed, network         naming services, in particular both the DNS and DNANS.  There         seems to be general agreement that distribution of naming         services should be done on the basis of nodes in the naming         structure, which also provide the basis for administrative         partitioning.  All the naming services described here support         distribution, partitioning of the information for placement on         cooperating servers.  Neither X.500 (and therefore Quipu) nor         Profile is prepared to redistribute portions of the namespace,         for reallocation of administrative responsibilities or load         balancing, although this should be possible and DNANS is         prepared to do so.  Replication is necessary for accessibility         in a large-scale or global namespace, although again X.500 does         not address this issue.  Quipu has taken a stand on this, by         defining master and slave copies of the data; it is similar to,         but not the same as, the approach taken in the DNS.  Caching is         barely touched on in X.500 and not at all in Profile, but ourSollins                                                        [Page 14]

RFC 1107         A Plan for Internet Directory Services        July 1989         experience with the DNS indicates that caching is critical to         effective operation of a distributed name service.  The DNANS         has an architected solution based on objects in the namespace         as the unit of distribution and replication.  Again, the DNANS         solution should be explored in the field test environment.      - Access control, accountability, and integrity:         Access control and accountability require some degree of         authentication.  X.500 supports authentication based on using         an RSA public key algorithm, but does not address issues of         universal registration, nor issues of access control or         accountability themselves.  These are left as a local issue,         although depending on the design of the system, they may have         global implications.  The problem of integrity of the         information in the name service is nowhere addressed.  Profile         also does not address these issues, although it uses         authentication based on UNIX authentication, involving user ids         and passwords.  DNANS takes a strong stand on access control,         architecting it in at the level of individual entries.  Field         trials will force these issues out into the open.      - Structure of the naming tree:         In the deployment of the DNS, about one year was lost to         arguments about the actual structure of the naming hierarchy.         People form strong opinions about their name, and fight for or         against certain hierarchical structures.  The same issue will         arise here, and advanced planning to deal with the problem is         required.         In this case, the problem is made harder by the fact that the         hierarchy will be global; X.500 is an international standard,         based on the assumption that there is only one example of the         tree, partitioned by country.  Probably the American White         Pages Service, at least at its root, will be run by the NIST or         its contractor.  We must deal with the problem that in the         short term, various implementations may not interwork, and we         must work with NIST to support the needed services.         Specific issues that come up related to the naming tree are:            * How is delegation of control of the tree managed?              For example, who decides what DSA holds what parts              of the tree?            * How is the creation of new parts of the tree              (e.g., an organizational entry) controlled?Sollins                                                        [Page 15]

RFC 1107         A Plan for Internet Directory Services        July 1989      - Support for Tree Search:         Regardless of the defintion of the white pages service in the         NRN, it will need to interface to the X.500 world.  The X.500         naming hierarchy can be expected to become very large, and         guidance is needed for users to help them navigate the tree.         Users need help to find their way to unknown parts of the         namespace.  As in other naming services, a feature of X.500 is         that additional entries, aliases (similar to links in file         systems) can be installed to provide an easy path for a user in         one part of the tree to find other interesting parts of the         tree.  By establishing a consistent policy for the use of alias         entries, learning how to navigate the tree can be made much         easier for a user.  As part of setting up the tree, therefore,         these sorts of policies need to be defined.      - Definition of database structures:         There are a number of data structures that need to be defined         as part of setting up each of the services.  These include, for         example, the types of information stored for the entry about a         person.  This information must be stored in the servers, and         passed to the clients.  These structures must thus be         specified.  In other words, the schema defining attributes and         object classes must be specified for the NRN.      - Load balancing:         The dynamic performance of the Internet system must be         estimated, so that the servers can be sized properly.         Especially at the root of the tree, the query rate must be         estimated carefully.  Caching will have a strong influence on         this.  Therefore, traffic patterns are very dependent on the         details of implementation.      - Supporting multiple protocol suites:         At least three protocol suites are and will continue to be used         in the NRN environment.  They are DECnet, TCP/IP, and the OSI         suite of protocols.  Since the white pages service is at the         applications layer, it must run on top of at least these three         protocol suites.  It is important to understand the         requirements of the white pages service for its transport         protocols.   By addressing these issues within the field trials, we will be   preparing for the further development of Stage 2.  A result of Stage   1 will be a detailed specification of the white pages service,Sollins                                                        [Page 16]

RFC 1107         A Plan for Internet Directory Services        July 1989   possibly an extension to or modification of X.500.  This should   dovetail with the activities specifying the details required for   implementation (known as "profiling") by the NIST Workshop for   Implementors of OSI.  In addition, in order to run the field trial,   the information capture problem must be addressed, providing the some   of the preliminary work of Stage 3.4.2. Stage 2: Implementation   If the evaluation of Stage 1 concludes that some form of X.500 is   acceptable, at least one of the two X.500 implementations included in   the field trials should provide the basis for a production quality   implementation of X.500 for general deployment.  Further work will   likely be needed on the basis of the evaluations of the field trials.   A production version of an implementation requires both reliable   servers as well as a variety of clients to provide differing   interfaces on a mixture of hardware and operating systems.   In addition, especially because of the inclusion of Profile and   DNANS, a variety of different DUAs will be explored by definition.   Further investigation into the DUAs should begin in parallel with or   in conjunction with the field trials.  There should be distinct DUAs   for both programs and humans.  In addition, there probably should be   human-user DUAs geared both to the naive user with simple usage   patterns and the more sophisticated user who wants to perform complex   queries.  It is also important to design DUAs that do not require a   great deal of computing power for the small machines still in use in   great quantity.  Much of the user community may not be able to afford   expensive equipment upgrades.   Assuming that X.500 is deemed to be the specification of the service,   the field trials will address many issues not included in X.500 as of   1989.  Since it is important for the NRN to support interconnectivity   beyond its own bounds, it behooves us to feed what has been learned   back into the standards activities.  This was identified as a   separate activity because of the intellectual as well as time   commitment that must be made to do this effectively.4.3. Stage 3: Deployment   A plan is required to develop the schedule of service introduction,   and to co-ordinate the deployment as it is undertaken.  This includes   mediating service problems, a significant task in its own right.   The details of deployment were not discussed at the meeting, although   several of the seeds of deployment lie in Stages 1 and 2.  The first   of these is the capture and management of information.  The second is   DUA development.  Both of these must be included Stage 1 in order toSollins                                                        [Page 17]

RFC 1107         A Plan for Internet Directory Services        July 1989   support a usable environment for the trials.  In addition, the   information that will have been captured in Stage 1 could be printed   producing a hard copy of the white pages information.  That could be   distributed to all scientists and engineers involved; such a project   would provide an early white pages service.  During the initial   periods of both Stages 1 and 2, planning for deployment would also   have to proceed, in order to provide a smooth transition to this   third stage in the project.5. Conclusion   The consensus of the meeting was that following a path that included   X.500 was both the correct direction and feasible, although X.500   needs further elaboration.  There were several important items for   further study.  The first is that there are many issues left   unresolved in X.500 that have been addressed in other naming   services, and the NRN should take advantage of the solutions in those   other services.  The second is that there was some reservation about   certain features of X.500, especially in the area of the imposition   of a hierarchy for naming, and only limited flexibility in   descriptive naming.  The participants believe that is important   understand whether X.500 provides enough mechanisms to work around   such problems by finding a higher common ground that includes the   best features of all the naming services included in the field   trials.  The final issue with respect to X.500 was that there was   agreement that X.500 will be an accepted and utilized standard in at   least part of the networked community and therefore interfacing to it   will be necessary.  Given that, and the other reasons for choosing   X.500, the consensus was that the plan described above would bring   the NRN and its community of users a useful and usable white pages   service.References   1.  Austein, R., "The Internet Domain Name System", Proceedings of       USA Decus, Massachusetts Institute Technology/LCS, 1987.   2.  Demers, A., D. Greene, C. Hauser, W. Irish, J. Larson, S.       Shenker, H. Sturgis, D. Swinehart, and D. Terry, "Epidemic       algorithms for replicated database maintenance", Proceedings of       the 6th Symposium on Principles of Distributed Computing, ACM,       Vancouver, B.C., Canada, pp. 12-21, August 1987.   3.  Digital Equipment Corporation, "DNA Naming Service Functional       Specification Version 1.0.1", Order number: EK-DNANS-FS-001,       Digital Equipment Corporation, 1988.   4.  International Organization for Standardization, "InformationSollins                                                        [Page 18]

RFC 1107         A Plan for Internet Directory Services        July 1989       Processing Systems - Open Systems Interconnection - The       Directory", Draft Standard (In 8 parts), Also CCITT       Recommendation X.500, 1988.   5.  Lampson, B., "Desiging a Global Name Service," Proceedings of the       5th Symposium on Principles of Distribute Computing, ACM,       Calgary, Alberta, Canada, pp. 1-10, August 1986.   6.  Mockapetris, P., "Domain Names - Concept and Facilities",RFC1034, USC/Information Sciences Institute, November 1987.   7.  Oppen, D., and Y. Dalal, "The Clearinghouse:  A Decentralized       Agent for Locating Named Objects in a Distributed Environment",       Tech. Rept. OPD-T8103, Xerox Corporation, Palo Alto, CA, October       1981.   8.  Peterson, L., "Profile: A System for Naming Internet Resources",       Tech. Rept. 20, Department of Computer Science, University of       Arizona, June 1987.Author's Address       Karen R. Sollins       Massachusetts Institute of Technology       Laboratory for Computer Science       545 Technology Square       Cambridge, MA 02139-1986       Phone: (617) 253-6006       EMail: SOLLINS@XX.LCS.MIT.EDUSollins                                                        [Page 19]