S 2.181 Selection of a suitable fax server

Initiation responsibility: IT Security Officer, Head of IT

Implementation responsibility: Head of IT

A fax server generally consists of the following components: the IT system itself, the operating system, the communications component (e.g. fax modem, active or passive ISDN card and/or dedicated fax card) and the actual fax server application. In addition, the workstation computers may require a corresponding fax client under certain circumstances.

Before a fax server is procured, the key factors affecting its usage must be ascertained first. They include:

IT system

The choice of the IT system is generally determined by the performance characteristics required by the software and the operating system. In addition, the IT system selected must be compatible with the operating system selected. Depending on the fax server availability requirements, the use of additional protection mechanisms can be considered. Options for ensuring and/or increasing availability include:

Operating system

Fax server applications are available for all commonly used network operating systems such as Unix, Microsoft Windows NT and Novell Netware. When selecting the operating system, the extent to which integration into the existing network is possible and the requirements of the fax server application should be the decisive factors. If only one network operating system has previously been in use in an organisation, e.g. only servers which run under Unix are used, then, if possible, this network operating system should be selected and an appropriate fax server application should be purchased. Nevertheless, if a particular software application is the only one to offer a feature which is urgently required but which will only run on a different operating system platform than that used up to now, then that operating system should be chosen. A change in the network operating system means a significant increase in administrative effort. If different network operating systems are already in use on the network, then the one which offers the easiest path to integration should be chosen provided that the desired fax server application supports it.

Communications component

The communications components establish the connection between the server and the public switched telephone network. Communications are processed using the T.30 protocol. This protocol determines, amongst other things, the connection setup, the exchange of the sender's fax number and the transmission and acknowledgement of the document. Transmissions using Group 3 standard are generally carried out at 9.600 bps and 14.400 bps. In addition, the Modified Huffmann, Modified Read and Modified Modified compression procedures are used. The Group 3 standard is the one most widely used. There is also a Group 4 standard; however, this requires ISDN. Using this standard, transmission rates of 64 Kbit per second can be achieved. The Group 4 standard has not succeeded in becoming as well established in the last few years, because appropriate stand-alone devices are relatively expensive. Moreover, the Group 3 and Group 4 standards are not mutually compatible.

At the start of the communication, both the transmission rate and the compression procedure are negotiated between the devices. The highest transmission rate and the best possible compression procedure which are supported by both devices are selected.

The following communications components can be considered when using a fax server:

a) Fax modem

Fax modems are available at a reasonable price. However, they are not always sufficiently resistant to manipulations and, in addition, are not supported by all fax server applications in continuous operation. Therefore, their use should be confined to private usage and to individual workstations.

b) Passive ISDN cards

Passive ISDN cards have a simple structure and are hence inexpensive. The main communication load is borne by the computer. This can be a problem when heavy use is made of the fax server (e.g. in the event of serial faxes). With passive ISDN cards, transmission using the Group 4 standard is generally also possible assuming that the recipient has an appropriate device. If fax data has to be transmitted according to the Group 3 standard, then the respective data has to be converted accordingly. As in the case of fax modems, passive ISDN cards should be mainly used only on an individual workstation or in the private domain.

c) Active ISDN cards

Active ISDN cards, also referred to as ISDN controllers, have their own processors. This means that they can handle the ISDN protocol largely independently. According to the specification of the Common-ISDN-API (CAPI), the fax data must be transmitted to the ISDN card in Structured Fax File (SFF) format. Conversion must take place on the fax server. Like modems, active ISDN cards only support transmission rates of 9.600 and 14.400 bps in the Group 3 standard, using the Modified Huffmann compression procedure.

A major disadvantage of both fax modems and active as well as passive ISDN cards is the fact that they can also be used for other purposes than fax transmission, e.g. in modem operation or as a remote access component. With a fax server, however, exactly such a situation is not desirable for reasons of network security. Active ISDN cards can make up to 30 ISDN channels available. When active ISDN cards are used, the ISDN signalling possibilities for automatic fax routing are also available. Despite the fact that they can be used for non-fax operations, active ISDN cards are still highly recommended for use in fax servers.

d) Fax cards (if necessary, with ISDN interface)

Special fax cards are optimised for handling the T.30 protocol. They assume the tasks of establishing the connection and "negotiating" the communications parameters. Data conversion and compression can be performed on the card. Thus, the load on the fax server is reduced considerably. There are fax cards offering the transmission of fax data at transmission rates of 9.600 and 14.400 bps and the application of all three compression procedures. These cards also have the advantage that they can generally handle only the T.30 protocol and, thus, cannot be used either for modem operations or as a remote access component. Some fax cards are enhanced by an ISDN interface. The advantage of this is that ISDN signalling options can be used for fax routing.

In summary, only active ISDN cards and fax cards should be used as a rule. The card must be compatible with the application software, as not every card is supported by all fax server applications. The number of cards required depends on the utilisation of the fax server. Transmission of approx. 40-50 pages of fax data is possible per hour and line and/or per channel.

Fax server application

When selecting the application software, both the volume of faxes to be processed using the fax server and the number of users need to be considered.

If an e-mail and/or workflow system is already available in the organisation, then it should be possible to integrate the application software using these systems. In this case, it may be desirable that incoming faxes and outgoing faxes are exchanged between the user's workstation computer and the fax server using the existing workflow and /or e-mail system. In this context, it is also of interest whether and how any existing address books and/or distribution lists can be synchronised with the fax server's address books. Moreover, archiving of incoming and outgoing faxes should be possible in the existing workflow systems.

Another factor to be considered is how fax messages should be transmitted from the user's workstation to the fax server and at what point the data should be converted into a data format that is compatible with the fax server. Conversion of outgoing fax data at the workstation is usually carried out using a printer driver or a special fax client application.

The converted data can then be transmitted to the fax server either by e-mail or else using the fax client application. One option is that the user copies the converted data to a special directory on the fax server. Finally, there are fax servers for which a printer queue is configured in the network. In this printer queue, the fax data is written by the application software, e.g. a text processing program. In addition, it is also possible that full data conversion is performed on the fax server. In this case, the user creates the file which is to be sent as a fax using appropriate application software, e.g. a text processing program, and this file then has to be sent to the fax server. This can be done by e-mail, an appropriate fax client application or by copying to a shared directory on the fax server. It should be borne in mind that conversion of the fax data at the workstation uses up resources which are available there. In general, this is not a problem if only a few faxes are sent each day. However, for serial fax messages in particular, this can mean that the workstation computer is blocked for a longer period of time. On the other hand, if demand is high at the fax server, conversion on it will require corresponding high-performance hardware and software.

When selecting suitable application software, final consideration should be given to the logging options which are available on the fax server. In addition to the error reports, transmission reports are also of interest. As a first step, the transmission reports for the relevant fax messages should be made available to the users using the fax server. This is the only way to ensure that users respond promptly, e.g. to connection errors. Furthermore, it should be possible to calculate the charges incurred from the transmission reports and to distribute them to the relevant cost centres.

Another influencing factor regarding the selection of the application software is the question how incoming faxes reach the recipients. Digital forwarding of incoming faxes using the network is also referred to as fax routing.

The option which is the simplest solution to implement from a technical point of view is, of course, to print out incoming faxes at a central location (fax mail centre) and to forward the printout to the recipient. The advantage offered by this solution is that the incoming faxes are printed out centrally for the files. In addition, incoming fax messages can be archived both digitally and manually. Furthermore, existing substitution arrangements can be adopted without any problems. One disadvantage, however, is the workload at the fax mail centre which might result from this under certain circumstances. Moreover, this approach means that the fax data is then not available in electronic form at the workstations.

Another option is that the fax mail centre sends the incoming faxes to the respective recipients by e-mail. This solution has also the disadvantage of generating extra workload for the fax mail centre. Here, each incoming fax is not printed out automatically. If such a printout is required for organisational or other reasons, appropriate rules and regulations must be established.

The following options are available for the automatic forwarding of incoming fax messages to the recipients using the network:

a) Line routing

Under this method, a fixed recipient is assigned to each line. The number of the recipients who are directly accessible is limited to the number of lines available.

b) Processing and identification of the call subscriber ID

A second approach involves assigning faxes on the basis of the transmitted call subscriber identification (CSID - Call Subscriber ID) of an incoming fax. Here, the fax server is instructed that incoming faxes sent by certain senders should be forwarded to a particular recipient. The disadvantage of this approach is that only incoming faxes from senders already known to the system can be forwarded automatically. All other incoming faxes must be forwarded manually to the recipients. Another problem is that there are no constraints on the selection of call subscriber IDs by the senders of faxes and that these IDs are thus not reliable under certain circumstances.

c) Signalling using ISDN

If ISDN is used, there are other automatic fax routing options. Here, a distinction must be made between the "multi-device connection" and the system connection.

With a multi-device connection, 2 lines and up to 10 telephone numbers are available for each connection. The telephone numbers are assigned by the respective telephone company. If the fax server is equipped with an ISDN card or a fax card with an ISDN interface, the recipient can be identified on the basis of the telephone number used by the sender. Due to the upper limit of 10 telephone numbers, it is thus only possible to distribute incoming faxes to a maximum of 10 recipients.

With an ISDN system connection, a private branch exchange system is switched between the public telephone network and the organisation's internal telephone network. With this type of connection, the fax server can also identify the telephone number used by the sender and, based on this number, automatically route an incoming fax to the appropriate recipient. With this solution, the maximum possible number of recipients is considerably higher. It is implemented by giving a second direct dial number to each employee expected to receive incoming faxes by the fax server. The PBX system forwards incoming faxes which arrive on this second number directly to the fax server. The only disadvantage of this approach is that a higher load is placed on the organisation's pool of telephone numbers. Thus, the private branch exchange system's performance must be adequately high.

d) Processing and interpretation of the recipient using optical character recognition

Another, but still not commonly used method of automatically routing incoming faxes is optical character recognition (OCR). Here, an attempt is made to identify names or numbers contained in the incoming fax, e.g. in the address field. This method requires powerful OCR software and appropriate computing power as well as standardised address fields in the incoming faxes wherever possible.

e) Other procedures

There are two other procedures for automatic forwarding of incoming faxes, i.e. the dual-tone multi-frequency (DTMF) procedure and the direct inward dialing (DID) procedure. Since both procedures cannot be applied in Germany, they are simply mentioned here for the sake of completeness.

Automatic forwarding of incoming fax messages offers the advantage of reducing the workload of the employees in the fax mail centre. In addition, this means that incoming fax messages reach the respective recipient more quickly. The main disadvantage of using ISDN signalling is that heavy workloads are placed on the pool of telephone numbers. This is, however, the most effective way of implementing the automatic forwarding of incoming fax messages. When the volume of incoming fax messages is high, preference should be given to this solution. If incoming fax messages are only sent to a few workstations and/or groups and are mainly received by the same senders, processing and interpretation of the call subscriber ID is also a practicable solution. If there is only a low volume of incoming fax messages, then manual distribution may be a viable alternative.

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