Internet-Draft Thommy Eklof
Category: Informational Ericsson
Expires: December 25, 1999 Leslie L. Daigle
Thinking Cat Enterprises
June 25, 1999
Wide Area Directory Deployment Experiences
draft-eklof-dag-experiences-00.txt
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that other
groups may also distribute working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on December 25, 1999.
Abstract
The TISDAG (Technical Infrastructure for Swedish Directory Access
Gateway) project provided valuable insight into the current
reality of deploying a wide-scale directory service. This
document catalogues some of the experiences gained in developing
the necessary infrastructure for a national (i.e., multi-organizational)
directory service and pilot deployment of the service in an environment
with off-the-shelf directory service products. A perspective on
the project's relationship to other directory deployment projects
is provided, along with some proposals for future extensions of
the work (larger scale deployment, other application areas).
These are our own observations, based on work done and general project
discussions. No doubt, other project participants have their own list
of project experiences; we don't claim this document is exhaustive!
1.0 Introduction
1.1 Overview of the TISDAG project
As described in more detail in [TISDAG], the original intention of the
TISDAG project was to provide the infrastructure for a national
whitepages directory service. To be effective, such an infrastructure
needed to address the concrete realities of end-users' existing client
software, as well as the needs of information providers ("Whitepages
Directory Service Providers" -- WDSPs). These realities include the
existence of multiple protocols (so-called directory service access
protocols, as well as more general Internet application protocols such
as HTTP and SMTP). The project was also sensitive to the fact that
WDSPs have many good reasons for being reluctant to relinquish copies of
their subscribers' personal data.
1.2 Organization of this document
In an effort to communicate the experiences with this project, from
conception through implementation and pilot deployment, this
document is divided into 3 major sections. The first section
reviews specific lessons learned by the authors through the TISDAG
project and implementation of one conformant system. Next, some
perspectives are offered on the relationship of the TISDAG work to
other large-scale directory projects that are currently on-going, to
give a sense of how these efforts might possibly interact. Finally,
some preliminary thoughts on applying the DAG system to other
applications and deployment environments are outlined. More speculation
on useful development of architectural principles is provided in
a separate document ([DAG++]).
2.0 The TISDAG project itself
2.1 TISDAG overview
Briefly, the technical infrastructure proposed for the TISDAG
project (see [TISDAG] for the complete overview and technical
specification) provides end-user client software with connection
points to perform basic whitepages queries. Different connection
points are provided for the various protocols end-users are likely
to wish to use to access the information -- WWW (http), e-mail (SMTP),
Whois++, LDAPv2 and LDAPv3. For each client, a transaction will
be carried out within the bounds of the protocol's syntax and
semantics. However, since the TISDAG system does not maintain
a replicated copy of all whitepages information, but rather an
index over the data that allows redirection (referrals) to services
that are likely to contain responses that match the client's query, a
fair bit of background work must be done by the DAG system in order to
fulfill the client's query.
The first, and most important step, is for the system to make a query
against the DAG Referral Index -- a server containing index
information (obtained by the Common Indexing Protocol (see [CIP])
in the Tagged Index Object format (see [TIO]). This index
contains sufficient information to indicate which of the many
participating WDSPs should be contacted to complete the query.
Wherever possible, these referrals are passed back to the querying
client so that it can contact relevant WDSPs directly. This
minimizes the amount of work done by the DAG system itself, and
allows WDSPs greater visibility (which is an incentive for participating
in the system). Protocols which support referrals natively include
Whois++ and LDAPv3 -- although these may only be referred to
servers of the same protocol.
Since many protocols do not support referrals (e.g., LDAPv2), and
in order to address referrals to servers using a protocol other
than the calling client's own, a secondary step of "query chaining"
is provided to pursue these extra referrals within the DAG
system itself. For example, if an LDAPv2 client connects to the
system, a query is made against the Referral Index to determine
which WDSPs may have answers for the query, and then resources within
the DAG system are used to pursue the query at the designated WDSPs'
servers. The results from these different services are packaged
into a single response set for the client that made the query.
The architecture that was developed in order to support the required
functionality separated the system into distinct components
to handle incoming queries from client software ("Client Access
Points", or CAPs), a referral index (RI) to maintain an index over
the collected whitepages information and provide referrals, based
on actual data queries, to WDSPs that might have relevant information,
and finally components that mediate access to WDSP whitepages
servers to perform queries and retrieve results for the client's
query ("Service Access Points", or SAPs). Several CAPs and SAPs
exist within the system -- at least one for every protocol supported
for incoming queries and WDSP servers, respectively.
Designed to be implementable as separate programs, these components
interact with each other through the use of an internal protocol --
the DAG/IP. Pragmatically, the use of the protocol means that
different components can reside on different machines, for reasons
of load-balancing and performance enhancement. It also acts
as a "common language" for the CAPs, SAPs and RI to express queries
and receive results.
This outlines the planned or ideal behaviour of the system; once
designed, a pilot phase was started for the project to compare
reality against expectations. Two independent implementations of the
software were created, and a test deployment was set up within the
Swedish University Network (SUNET). More detail on the project and its
current status can be found at http://tisdag.sunet.se/.
The rest of this section outlines some conclusions drawn from
making a reality of the proposed architecture -- both successes and
surprises.
2.2 Some successes
Implementation and pilot deployment of software meeting the TISDAG
technical specification did demonstrate some important successes
of the approach.
Most notably, the system works pretty much as expected (see exceptions
below) to provide transparent middleware for whitepages directory
services. That is, client software and WDSP servers were minimally
affected -- from the point of view of behaviour and configuration,
the DAG system looked like a server to clients, and a client to servers.
The DAG system does demonstrate that it is possible to build
referral-level services at a national level (although the deployment
has yet to prove conclusively that it can, in its current
formulation, operate as a transparent query-fulfillment proxy
service).
The success of the implementation demonstrated that it is possible,
in some sense, to do (semantic) protocol mapping with N+M complexity
instead of NxM mappings. That is, protocol translations had to
be defined for "N" allowable end-user query access protocols to/from
the DAG/IP, and "M" supported WDSP server protocols, instead of
requiring each of the N input components to individually map to
the M output protocols.
As a correlated issue, the prototype system demonstrated some
successes with mapping between schema representations in the
different protocol paradigms -- in a large part because system's
schemas were kept simple and focused on the minimal needs to support
the base service requirements.
2.3 Some surprises
Over the span of a dozen months from the first "final" draft of
the specification through the implementation and first deployment
of the software system, a few surprises did surface. These
fell into two categories: those that surfaced when the theoretical
specification was put into practice, and others that became apparent
when the resulting system was put into operation with commercial
software clients and servers.
More detail is provided in the Appendix concerning specific
software issues encounterd, but some of the larger issues that surfaced
during the implementation phase are describe below.
2.3.1 LDAP objectclasses and the "o" attribute
It came as a considerable surprise, some months into the project,
that none of the "standard" LDAP person objectclasses included
organization ("o") as an attribute. The basic assumption seems to be
that "o" will be part of the distinguished name for an entry, and
therefore there is little (if any) cause to list it out separately.
This does make it trickier to store information for people
across multiple organizations (e.g., at an ISP's directory server) and
use the organization name in query refinement. (Roland Hedberg caught
this issue, and has flagged it to the authors of the "inetorgperson"
objectclass document).
2.3.1 The Tagged Index Object
The Tagged Index Object ("TIO"), used to carry indexes of WDSP
information to the RI, is designed to have record (entry) tags to
reduce the number of false positive referrals generated when doing a
search in the RI. One of the features of the first index object type,
Whois++'s centroid (see [centroid]) was the fact that the index object
size did not grow linearly with the size of data indexed -- i.e., at
some point the growth of the index object slowed as compared to that of
the underlying data set. At first glance, this also seems to be the
case for the TIO. However, as the index grows in size the compression
factor of the TIO may not achieve the same efficiency as the centroids.
One reason for this is that the tagged lists can get quite long,
depending on the ordering of the assignment of tags to the underlying
data. That is, the tagging as defined allows for a compressed
expression of tag "ranges" -- e.g., "1-500" instead of "1,2,3,[...]500".
Thus, it might be interesting to explore an optimal "sorting" of
underlying data, before applying tags, in order to arrange the
most common tokens have consecutive tags (maximal compression of the
tag lists). It's not clear if this can be done efficiently over
the entire set of records, attributes, and tokens, but it would bear
some investigation, to produce the most compressed TIO for transmission.
Additionally, in order to make (time) efficient use of the tags in the
RI in practice, it is almost necessary to "reinflate" the index object
to be able to do joins on tag lists associated with tokens that match.
Alternatively, the compressed tag list can be stored, and there is an
additional cost associated with comparing the tag lists for matching
tokens -- i.e., list comparison operations done outside the scope of a
base database management system. There was an unexpected tradeoff to
be made.
2.3.3 Handling Status Messages
Mapping of status messages from multiple sub-transactions into a single
status communication for the end-user client software became something
of a challenge. When chaining a query to multiple WDSPs (though the
SAPs), it is not uncommon for at least one of the WDSP servers to
return an error code or be unavailable. If one WDSP cannot be reached,
out of several referrals, should the client software be given the
impression that the query was completed successfully, or not? Most
client protocol error handling models are not sophisticated enough to
make this level of distinction clear.
2.3.4 Deployment with Commercial Software
When it then was time to test the resulting software with standard
commercial client and server software, a few more surprises came
to light (primarily in terms of these softwares' expected worldview
and occasional implementation shortcuts). Again, more detail
is provided in the Appendix, but highlights included client
software that could only handle a very small subset of a protocol's
defined status message lexicon (e.g., 2 system messages supported),
and client software that automatically appended additional terms
to a query specified by the user (e.g., adding "or email=<what
the user typed in to the query>").
2.4 Some evolutions
To date, the TISDAG project has been "alive" for just over two years.
During that time, there have been a number of evolutions -- in
terms of technologies and ideas outside the project (e.g., user
and service provider expectations, deployment of related software, etc)
as well as goals and understanding within the scope of the project.
Chief among these last is the fact that the project set out to
primarily fulfill the role of a national referral service, and
gradually evolved towards becoming more of a transparent protocol
proxy service, fulfilling client queries as completely as possible,
within the client protocol's semantics. This evolution was probably
provoked by a number of reasons -- existing client & server software
has a narrower range of accepted (expected) behaviour than their
protocol specs may describe, once the technology was there for
some proxying, going all the way seemed to be within reach, etc.
From the point of view of providing a national whitepages service,
this is a very positive evolution. However, it did place some
strains on the original system architecture, for which some
adjustments have been proposed (more detail below). What is less
clear is the impact this evolution will have on the flexibility
of the system architecture -- in terms of addressing other applications,
different protoocols (and protocol paradigms), etc. That is,
the original intention of the system was to very simply fulfill an
unsophisticated role -- "find things that sort of match the input
query and let the client itself determine if the match is close enough".
As the requirements become more sophisticated, the simplicity of the
system is impacted, and perhaps more brittle. (Some proposals for
avoiding this are outlined in [DAG++], which attempts to return to
the underlying principles and propose steps forward at that level).
In terms of impact within the TISDAG project, this evolution lead
to the following technical adjustments:
. The latest version of the technical specification makes
a distinction (in the internal protocol grammar) between
queries directed at the Referral Index, and those passed
to SAPs to fulfill a query. This distinction keeps the
query-routing queries simple, but allows more sophistication
in expressing a query designed to fulfill the client's
original semantic expression.
. The additional constraints in the SAP query language
is still not enough to allow the internal protocol to
express very sophisticated queries. Originally intended
only for query-routing queries, the DAG/IP expects all
queries to be token-based (whereas LDAP queries are
phrase-oriented). This means that SAPs have to do
a good deal of "post-pruning" of WDSP result sets to match
the DAG/IP query sent by a CAP for query fulfillment.
And, CAPs must in turn do more post-pruning to match
the DAG/IP results (from the SAPs) to the original query
semantics.
The real strength of the TISDAG project was that it separated
the technical framework needed to support the service from
the configuration required in order to support a particular
application or service -- query & schema mapping, configuration
for protocols, etc. Future improvements should focus on
evolving that framework, maintaining the separation from the specific
applications, services, and protocols that may use it.
3.0 Related Projects
The TISDAG project is not alone in attempting to solve the problems
of providing coordinated access to resources managed by multiple,
disparate services.
3.1 The Norwegian Directory of Directories (NDD)
Described in [NDD], the Norwegian Directory of Directories project
also aims to provide necessary infrastructure for a national
directory service. It assumes LDAP (v2 or v3) accessibility
of WDSP information (provided by the WDSP itself, or through
other arrangements), and aims to resolve some of the trickier
issues associated with hooking together already-operational LDAP
servers into a coherent network: uniform distinguished naming
scheme, and content-based referrals. It also addresses some of the
pragmatic realities of being compatible with different versions
of LDAP clients -- e.g., v2, which does not support referrals, and v3,
which does.
At the heart of the system is the "Referral Index and Organizational
information" (RIO) server, which provides a searchable catalogue
over Norwegian organization. This faciliates the location of
whitepages servers for individual organizations (assuming the
query includes information about which organization(s) is(are)
interesting).
This work can be seen as being complementary to the TISDAG work,
in that it provides a more focused service for integrating LDAP
directory servers. However, there is still some requirement that
one knows the organization to which a person belongs before doing
a search for their e-mail address. This may be reasonable for
seeking mail addresses associated with a person's work organization,
but is less often successful when it comes to finding a personal
e-mail address -- in an age where ISPs abound, a priori knowledge
of a user's ISP identification is unlikely.
3.2 DESIRE Directory Services
The EC funded project DESIRE II (http://www.desire.org) is developing a
distributed European indexing system for information on Research and
Education. The Directory Services work undertaken by DANTE and SURFnet
proposes an architecture applied to a server mesh structure to create a
wide-area directory service infrastructure.
This service is intended to support both whitepages information with
LDAP servers at WDSPs, as well as a Web-search meshes at various places
using Whois++ for information about resources and routing of queries to
other index-based services.
Like the TISDAG project, the DESIRE directory services project
aims to act as a focal point for queries, allowing client software
to access appropriate resources from a wide range of disparate
services.
There are architectural differences between the approach used in
the TISDAG project and the DESIRE directory service project, but
many of the driving needs are the same, and the approach of using
content-based indexing and referrals was also selected.
4.0 Some Directions for TISDAG Next Steps
The fun thing with technology is that there are always more tweaks
and changes that can be made. However, a service should evolve
in response to specific customer needs, and there are 2 critical
ways in which the TISDAG service itself should advance. These are
outlined below, without specific recommendation for underlying
technology changes that would be necessary to fulfill them.
4.1 Integrating multiple DAG networks: mesh.
The Common Indexing Protocol is designed to facilitate the creation
not only of query referral indexes, but also of meshes of
(loosely) affiliated referral indexes. So far, the TISDAG project
has focused on creating a single referral index; the obvious next
step is to integrate that into a larger set of interoperating services.
Two different possibilities are possible for extending the TISDAG
service to a mesh model (or some combination of both). First, it
should be possible to create a mesh of DAG-based services. Or,
it might be interesting to use the mesh architecture to incorporate
access to other types of services (e.g., the Norwegian Directory
of Directories).
The basic principle for establishing a mesh is that interoperating
services should exchange index objects, according to the architecture
of the mesh (e.g., hierarchical, or graph-like, preferrably without
loops!). As is outlined in the CIP documentation ([CIP]), many
possibilities exist for mechanisms for creating indexes over multiple
referral servers -- for example, WDSP index objects could be passed
along untouched, or a referral index server's contents could be
aggregated into a new index object, generating referrals back to that
server.
The proposal is that the mesh should be constructed using index
objects aggregated over participating services' servers. That is,
referrals will be generated to other recognized services, not
their individual participants. This can be done as a hierarchy
or a level mesh one-layer deep, but the important reason for
not simply passing forward index objects (unaggregated) is that
individual services may support different ranges of access protocols,
have particular security requirements, etc. Referrals should
be directed to a CAP or CAPs -- either the standard ones used
by the DAG system, or new ones established to support particular
semantics of remote systems (e.g., other query types, etc). Within
a given DAG system, referrals to these remote servers will look
just like any other referral, although a particular SAP or SAPs
may be established to provide query fulfillment (again, to
enable translations between variations of service, to allow
secure access if the relationship between the services is restricted,
etc).
It will be necessary to make use of the "polled-for" and "polled-by"
constructs of the DAG/IP to allow individual CAPs to navigate
around the mesh -- if no referrals are found in the local server,
what other servers might be canvassed?
It may be useful to allow individual WDSPs to indicate whether they
are willing to have their data included in a DAG system's aggregated
index object (i.e., allowing the DAG system to receive referrals
from other systems in the mesh).
4.2 Security support
There is a need for security considerations when making use of a
wide-scaled directory system in other application areas than
the public white-pages application of the TISDAG project. There
are issues whether the directory service is distributed across the
Internet, or even if it functions completely within an internal,
closed network.
In the medical area, searching for patient information over multiple
hospitals and other institutions within the health-care community, the
requirements for security are very high. The DAG-system applied to
medical application should only be integrated with the existing security
model already implemented in the health-care community; the use of
DAG in a medical application will have impact on the DAG-system's
security architecture. Proposals for such a system are presented
elsewhere, but some of the specific requirements are listed below.
In an internal closed hospital network, it is possible to expect
dedicated, application-specific interfaces and protocols. For
this client software, the specific steps of achieving authorization
and carrying out the transaction should be welded into a single
service interaction. The DAG-system needs support for a uniform
authentication and authorization service interface for facilitating
access control decisions and requesting access control information
about users, roles, organisations.
For example, access control requirements of a medical application
may include:
- authentication of the user, e.g. doctor
- authorization, classified by roles for individual users, roles and
organizations
- time availability, e.g. time of the day or day of the week
- encryption of the information
- required confidentiality/integrity information protection
based on relation to users, roles and organisations.
- secure network communications, host properties
Security in updates and CIP index objects is provided by encryption and
signature of objects from registered WDSPs. Using CIP index objects
inherits the security considerations of CIP, for more details see [CIP].
5.0 Other applications of DAG
One of the tests of flexibility of an architecture is to see how
well it stands up when tried in new environments. In that light,
we present 2 completely different applications in which DAG-like
systems can be considered.
5.1 DAG as applied to medical applicationns
As alluded to above, the need for accurate and complete information is
very large within the health-care community. The information about
patients can not be centralized from all different institutions
that own and administrate the data. Patients do not always face the
same doctor or even go to the same hospital or clinic within the
community. Instead of requiring centralized mirroring of complete
information and to avoid rebuilding the whole structure for information,
the DAG can be used as a gateway which interconnects the different
patient records databases within a hospital or within a geographical
area.
There is some architectural differences to apply DAG to medical
application such as definition of schemas and security considerations.
5.2 Wireless access to DAG
The ability to provide differentiated forms of access to directory
service information will be very important in the future. Particularly
in the context of wide-area directory deployment (such as white pages
services for companies and operators, but also over multiple operators,
etc) will be very important in the future. Users will demand to access
information from their PC at work or at home, from PDA's and from
cellular phones (wireless).
Wireless Application Protocol -- WAP, as specified in [WAP] and other
forms of access are providing new ways to access the Internet. Cellular
phones that can handle WAP (i.e browser functionality in the phone)
are already on the market, as well as operators running WAP server
functionality in their cellular phone networks.
The architecture of DAG is very modular and facilitates the addition
of new CAPs, such as a "WAP-CAP" or other supported protocol by WAP
servers.
Using WAP as an access mechanism would enable a person to have access
to their personal address book, a company or operator's directory
service. This information could be used for several other services:
voice calling, click to dial, click to buy etc. The advantage here is
that the directory service provides a context for the user. This
context, or the search to the directory service, must be limited,
for example to avoid an overgeneralized query and too many hits
for the query.
Providing this type of service will also be useful in the context
of Unified Messaging Services. Unified Messaging services are becoming
more and more used today -- the user recieves an email which is
forwarded to their cellular phone. A wide area directory system, such
as a DAG system, could be used to facilitate things like searches for,
or lookup of the E.164 number for an email adress. Of specific
interest is that this would allow searches for information over
multiple operators.
Like the TISDAG project's pilot deployment, this section only describes
"read-only" access from different clients to the DAG-system. In
the longer term, it would be useful to distinguish between reads,
searches/lookups and writes. This suggests that proper integration
with the Authentication, Authorisation and Accounting (AAA policy)
is needed for the different accesses to DAG. This security issue have to be
addressed again and more about that is provided in a separate document
([DAG++]).
6.0 Some conclusions
Although fewer people now hold out the hope of a unified global
directory service, based on standardize protocols, it is interesting
to see more projects providing infrastructure that permits unified
access to what is otherwise an unforgivingly diverse and dislocated
set of information servers. What cannot be dictated (in standardized
protocols and schemas) may yet be accommodated through service
infrastructure. The right approach seems to be to build better and
better frameworks for supporting such diversified services, without
making the framework architecture dependent on specific technologies.
7.0 Acknowledgements
This document outlines the perspectives and opinions of the authors,
based on experience as well as many fruitful and enlightening
discussions with others: Roland Hedberg, Torbjorn Granat, Patrik
Granholm, Rikard Wessblad and Sandro Mazzucato.
8.0 Authors' Addresses
Thommy Eklof
Ericsson
S-126 25 STOCKHOLM
Sweden
Email: thommy.eklof@ericsson.com
Leslie L. Daigle
Thinking Cat Enterprises
Email: leslie@thinkingcat.com
9.0 References
Request For Comments (RFC) and Internet Draft documents are available
from numerous mirror sites.
[CIP] J. Allen, M. Mealling, "The Architecture of the
Common Indexing Protocol (CIP)," Internet Draft
(work in progress), November 1998.
[CIP] J. Allen, M. Mealling, "MIME Object Definitions for
the Common Indexing Protocol (CIP)," Internet Draft
(work in progress), June 1997.
[CIP] J. Allen, P. Leach, R. Hedberg, "CIP Transport
Protocols," Internet Draft (work in progress), April
1999.
[DAG++] L. Daigle, T.Eklof, "An Architecture for Integrated
Directory Services, "Internet Draft (work in
progress), June 1999
[TISDAG] L. Daigle, R. Hedberg "Technical Infrastructure for
Swedish Directory Access Gateways (TISDAG)," Inter-
net Draft (work in progress), June 1999
[centroid] Deutsch, et al., "Architecture of the WHOIS++ service",
RFC 1835, August 1995.
[NDD] R. Hedberg, H. Alvestrand, "Technical Specifica-
tion, The Norwegian Directory of Directories
(NDD)," Internet Draft (work in progress), May 1999
[TIO] R. Hedberg, B. Greenblatt, R. Moats, M. Wahl, "A
Tagged Index Object for use in the Common Indexing
Protocol," Internet Draft (work in progress),
December 1998.
[WAP] The Wireless Application Protocol,
http://www.wapforum.org
Appendix -- Specific Software Issues and Deployment Experiences
The following paragraphs outline practical deployment experiences
in an anecdotal fashion. This is not meant to be construed as
an exhaustive, authoritative evaluation of existing client software,
but rather an indication of the types of challenges the average
implementation team may expect to encounter in a development and
deployment effort.
Character encoding
------------------
One client's addressbook sends iso-8859 encoding (depending on the
font configuration in the browser) when querying a directory server but
the directory server responds with Unicode (UTF-8) encoding. This means
that the LDAP CAP would have to handle different character set
encodings for request and response.
Referrals
---------
Today there appears to be only one commercial addressbook supporting
LDAPv3. All the others support only LDAPv2. However, this LDAPv3
client software does not handle referrals correctly -- the client
couldn't handle server the result contains "response code 10"
(designated for referrals). From what was observed, there was
now way for the client or the end-user to decide if, or which,
referrals to follow-up. It is therefore not clear how the LDAP
clients handle a combination of both referrals and results -- but
the supposition is that it doesn't work.
Objectclasses in LDAP
---------------------
No objectclass is defined in the query to the DAG-system from the
LDAP-clients. This means that the DAG-system doesn't see any differences
between "inetOrgPerson" and "organisationalRole" when attribute "cn" is
representing both "name" and "role". This is not so much a problem
as that it has interesting side effects. Namely, although most
directory user interfaces (found in browsers, mail programs) claim
only to support person-related queries, in practise a user of the
client could use the interface to send a query with role in the name
entry.
Query with attribute Organisation
---------------------------------
It is possible to send a query with attribute "organisation" but it
would result in no hits because of that the organisation attribute is
not included in the objectclass "inetOrgPerson". Roland Hedberg has
proposed a change for the next (latest?) release of the objectclass
definition document.
To provide the desired ability to narrow search focus to some
range of organization names (attribute values), there are three
possible approaches with differing merits/detractions:
Recommend the use of the "locality" attribute -- although
a more standard definition would be required (locality is
currently used for everything from organization to county
to map coordinates).
Recommend or require that the attribute organisation should be
inherited in objectclass "inetOrgPerson".
Build the LDAP DAG-SAP to submit 2 query to the WDSP. The second
is the same as the first, with only cn filters if the entire
query including "o" results in no hits (i.e., back off from
the organization filtering if it doesn't seem to be supported).
Configuration
-------------
It is not possible to see what character set a LDAP client want to use.
The recommendation so far in he project has been to define a unique
port for each character set. This requires extra end-user configuration
of client software, and proper advertizing of the port number-charset
mapping provided in the service.
DN
--
When the user wants to look-up more information about a person found
in a preliminary search, the LDAP client uses the entry's DN together
with host and port to the DAG system. Not only does that mean
that the client submits a non-compliant query to the DAG system,
as DNs are not part of any of the defined queries for the service,
it simply does not provide the desired effect of getting to the
user's entry.
Response Codes
--------------
The LDAPv3 client that was used does not support more than 2 response
codes -- "success" and "size limit exceeded". All the other response
codes are translated to "size limit exceeded", although no
results are returned. That is, if the error was in fact that
the size limit was exceeded, the results up to the size limit are
presented. If it was another response code mapped to that one,
no results are presented.
Sending and loading CIP Index Objects
-------------------------------------
At least one server is quoting the CIP-object incorrectly for
the Swedish characters Ê,ý, Ù. Sending quoted printable CIP-objects
with PINE mail software works.
Source - Labeled URI
--------------------
The original plan for the use of the labeled-URI attribute was
to use it to return a pointer to the WDSP that provided the user
information. However, the standard use of the labeled-URI attribute,
which may in fact be populated in the data returned by a WDSP, is
to contain the URI for more private related homepages.