IT Baseline Protection Manual - The Information Warfare Site

Safeguard Catalogue - Communications Remarks
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S 6.69 Contingency planning and operational
reliability of fax servers
Initiation responsibility: Head of IT Section, IT Security Management
Implementation responsibility: Administrator, fax mail centre
Measures for contingency planning and operational reliability of fax servers
depend on the volume of material processed over the fax server(s) and the
required availability of this service.
As a first step all configuration parameters for the communications cards,
operating system and fax server application used must be documented.
Whenever the configuration is changed, the documentation must be updated
accordingly. Only in this way will it be possible to reinstall a fax server in the
shortest possible time in an emergency.
Moreover, data backups should be performed at regular intervals, as stipulated
in the data backup policy and the security policy. Backups should not be
confined to the data partitions but also cover the partitions on which the
operating system and the fax server applications are located.
The fax transmissions stored on the fax server must be backed up at regular
intervals. Where permanent archiving of fax data is desirable, this should be
performed not on the fax server but on external data media.
One or more conventional fax machines should be held in reserve so that in
the event of failure of the fax server or the network it is still possible to send
and receive faxes. The number of machines required depends on the volume
of incoming and outgoing fax transmissions in emergencies. It is sensible to
keep the fax machines which were used prior to installation of the fax server
as an emergency fallback.
All other available measures aimed at increasing operational reliability are
expensive and should therefore only be considered where availability is very
important. Such measures should be considered on a case-by-case basis.
As a first step, the IT system on which the fax server is installed can be
equipped with a RAID system. This entails merging several hard disks into a
single pool and distributing the data contained on them in such a way as to
ensure data redundancy. With RAID level 5, this means that if one hard disk
fails no loss of data occurs. However, when RAID technology is used, it has
the effect of reducing the overall capacity of the hard disks due to the creation
of redundancy. It should also be remembered that this solution is no substitute
for external data backups, nor does it protect against total failure of the
system.
Operational reliability can also be achieved through the use of several fax
servers. If one server fails, the load can be distributed over the other servers.
Another advantage of this solution is that the load is split so that the danger of
overloading one individual fax server is reduced. On the other hand, any
incoming fax transmissions which are located on the failed server will not be
available at least for the duration of the failure.
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IT-Baseline Protection Manual: Oktober 2000
Document configuration
parameters
Regular data backup
Hold conventional fax
machines in reserve
Use of RAID systems
Use of several fax
servers