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4.3. The Production Phase
The production phase started January 1, 1995. According to the results of the introduction phase it was
immediately clear that we need a much more powerful machine for this phase. But to minimise costs as well as
administration overhead we continued to run all services on a single machine which was sponsored by GMD.
We placed the machine on a separate service net.
Figure 1: System structure
Via a firewall system this service net is linked to GMD's IP backbone [Chapman and Zwicky 95]. As a member
of GMD's Technopark gekko is also connected to the central backbone. Beside the service machine we
installed a modem pool at the service net which users can connect to for retrieving information from the
servers. Our infrastructure is completed by an ISDN router which is connected to GMD's backbone. One of its
interfaces is reserved for use by DW only to transfer raw text material from DW to gekko for conversion into
HTML as well as to give some selected employees of DW full Internet access via GMD.
We used standard software (NCSA's httpd, ftpd from the Washington University in St. Louis, freeWAIS and
sendmail [NCSA 95, Liu et al. 94, Costales et al. 93]) for realising all services due to their rich functionality
and widely usage within the Internet community. Especially, we used a public domain Web server because no
matured commercial server was available at that time.
Also the migration to our new server machine at the beginning of the production phase was smoothly and
nearly transparent to the users. One service after the other was transferred by changing its DNS entry after
preparing the service on the new machine. At the beginning, some users and programs (especially Web crawler
for indexing entire Web sites) continued to use the old IP address. Thus, for a transitional period we kept the
old servers running but pointing any users to the new machine.
To guarantee and to verify our quality of service agreements we monitor the hardware with our internal
SNMP-based network management system [Eisenblätter et al. 93, Case et al. 1990]. Using these mechanisms
we are also able to detect any violations of agreed resource limits (like e.g. Internet bandwidth) and to obviate
them if necessary. For the beginning we also manage DW's ISDN connection to GMD. We keep access data for
all services as well as the router utilisation in order to produce our monthly usage statistics. Backups of the
data areas are made automatically over night.