WASD Hypertext Services - Technical Overview
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1 - Introduction
As of July 1997 High Frequency Radar Division (HFRD) underwent a change of
role and name. It is now Wide Area Surveillance Division (WASD). This package
has been renamed in accordance with that.
This document provides an technical overview of the WASD VMS HyperText
Transport Daemon environment. It is primarily written for use internal to
WASD and assumes that perpsective without apology. Any additional usage is
subordinate to its role within WASD. The software has been written expressly
for supporting an intra-organisational hypertext environment on a VMS
platform (June 1997 note: since first writing this the industry has settled
on the term Intranet). It too, is unreservedly tailored to
this purpose and the requirements of WASD. All programs were designed only
to specifically comply with the requirements of VAX C and DEC C, within a DEC
TCP/IP Services for VMS environment.
The document assumes a basic understanding of the
hypertext technologies and uses terms without explaining them (e.g. HTTP,
HTML, URL, CGI, SSI, etc.) The reader is refered to documents specifically
on these topics (these are often best consulted on-line, on the Internet WWW).
Also see
WASD Hypertext Environment
for information on using the WASD VMS hypertext facilities.
Reasons For a Local HTTPd
Reasons for developing a local HTTPd server are few but compelling:
- The WASD (then HFRD) Web implementation begain mid-1994 (October 1997
note).
- It was prefered to support the hypertext environment on a VMS platform.
This is currently (1995) the most widely used and accessable environment
within WASD.
- Existing servers (and there are quite a few variations) are largely Unix
based, although it is being supported (to a greater or lesses extent) across a
wide range of platforms. Ports to VMS, if they exist, are often in progress
or half-baked, employing Unixisms that don't translate elegantly
to the VMS environment.
- The VMS version of the CERN server (3.0-6) was evaluated during mid-1994:
- It is not multi-threaded under VMS (i.e. cannot support concurrent
clients). For example, a lengthy search may delay other clients for
unacceptable periods.
- Its performance was good with document transfers, but became poor when
running a script.
- It is acknowleged in the release notes that it cannot handle a client
cancelling a data transfer (a not-uncommon action). This was confirmed
experimentally.
Future versions of this server should be evaluated periodically as it is
receiving a good deal of support and attention.
- HyperText Transport Protocol, in its current form, is relatively simple
to implement to the level required to support intra-Divisional requirements.
- As of December 1995 the server has worked extremely
well and has a number of facilities tailored for the VMS environment. It can
continue to be utilized until there are overwhelming reasons for implementing
something else.
- As of June 1997 the server and its associated software
continues to evolve and provide a stable and effective VMS Web environment,
even with the advent of a small number of commercial VMS Web products.
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