Recent developments have established LDAP as a popular access method to directory systems. X.500 DAP is perceived by some people as being too complex and bearing too heavy a requirement on hardware. The flipside to this is that though the competing technologies are simpler, they often lose out in terms of flexibility and overall functionality.
X.500 (the Isode Limited implementation in particular) has been adopted as the base technology for EuroView because of its ability to interoperate in an environment employing several transport protocols. This is a very important factor as the set of validation sites are connected via different networks, using either TCP/IP or X.25. Having said this, the infrastructure will utilize the Internet for basic connectivity. Users of X.25 will in effect be patched in to the service using gateway services.
It should be noted that use of a single implementation would not be recommended in a wider service, in order to promote real interoperability and to promote vendor competition.
Service access will be provided using a range of access protocols, including DAP, LDAP, and HTTP.
Well designed service infrastructure is the most important aspect of any networked service. This is especially true of the EuroView service due, mainly, to problems presented by the multi-protocol environment of the pilot users. The requirement for rapid response times (ideally in the range of a few seconds) aggravates this. The directory contrasts with services like electronic mail where relatively lengthy latency times between request initiation (mail submission) and completion (mail receipt) are the norm. As a result, acceptable service levels are somewhat more difficult to attain.
Factors affecting integration and performance are:
• Network connectivity/available bandwidth.
• Transport protocols used, and the resulting need for gateways.
• The number of systems involved.
• Level of data replication employed.
• Database sizes, and how well implementations cope with these.
• Security requirements, especially with regards to use of firewalls.
Much of the detail of this document is a direct response to the needs of the validation sites as reported in the "EuroView User Survey". Case by case detail is provided where necessary, especially when the needs of a particular site are problematic or unusual.