X.500 Directory Services

Introduction

Amount of information available online is exponentially exploding
This wealth of information is only useful if you can locate what you are after
Searching for information on that obscure product in Zimbabwe?
Looking for that printer in the head office of a multinational corporation to send your resume to?
Directory Services to the rescue!

Data Defense Network Network Info Center
- Assigns and tracks IP addresses
- Large central DB
- Slow, inacccessable if one link goes down
Domain Name Service (DNS)
- Map names to IP (Internet Protocol) addresses (ie. fsj.cpsc.ucalgary.ca = 136.159.2.10)
- Distributed, backup machines
- Fast, well suited to task
- Not suitably flexible to track other information
- Poor search capabilities

Primarily business oriented ITU-T (International Telecommunications Union - Technology, formerly the CCITT) standard
Globally distributed hiearchical directory database
Decentralized maintenance (each site responsible for it’s own tree
Powerful search engine allows complex queries
Sinlge homogenus namespace; more expandable and flexible than that used by DNS
Enforced standard allows for easy and universal application access (Lotus Notes, SAP)

Database consists of entities belonging to object classes; each entity contains standard and definable attributes
Examples of object classes: Country, Organization, Organizational Unit
The object classes define permissable DB structures
The Directory Information Tree (DIT) stores all data
The complete tree is dsitributed globally across the world
Users can directly access the directory through a Directory User Agent (DUA) client
Portions of the DIT can be replicated on numerous servers for efficiency
Extensive security features allow selective access to specific areas of the tree depending on the user id
Aliasing allows a relational component to be added to the DB
Tree design is very complex, many tradeoffs and design philosophies
Reorganization of the tree structure can be enormous undertaking (X.700 anticipated to remedy this however)

Technology of Star Trek computers
- "locate xxx", tell me about "yyy" and computer will be able to
Best suited to static data, but pointers can be created to handle dynamic information
Boasting a very high utility, X.500 provides an excellent solution to the biggest problem facing the information highway.

References/Further Information:

Sample X.500/WWW Gateways to non-production X.500 directories

Other sections: