Data communications system for the state of Nordrhein-Westfalen

Data communications system for the state of N ordrhein-Westfalen W KOhler outlines an open communications system developed prior to international standardization The common data communications system for the German federal state of Nordrhein-Westfalen has been established to provide communications between different vendors' computers within the state administration. The system uses manufacturer-independent protocols such as X.25 (Layer 3), EHKP4 as the transport protocol (Layer 4), and protocols for file transfer and dialogue (line-mode). Network management facilities, and a centre for testing services, protocols and interfaces are in operation. The virtual terminal protocol is described in some detail, as the service has only recently been developed.

with administrative responsibilities shared by the federal government and the federal states. The government of the federal state of Nordrhein-Westfalen (NRW)is based in DC~sseldorf, but the state administration's offices and institutions are spread over a wide geographical area, mainly focused in the larger towns. Within these locations there are hundreds of Data Processing (DP) systems, covering a wide range of specifications and capabilities, and supplied by a number of different computer manufacturers. To enable communication to take place between the various computer centres, the Department of the Interior (responsible for DP planning and coordination) gave the task of developing a state-wide data communications system to the Landesamt f(~r Datenverarbeitung und Statistik (LDS). The LDS is the main DP centre of the state administration I .

Keywords: data communications, Open Systems Interconnection, telecommunications, data processing, virtual terminal protocols

DATENVE RM IT'rLU NGSSYSTE M NORDRHEIN-WESTFALEN (DVS)

The Federal Republic of Germany (FRG) is divided into 11 federal states,

Work on the Datenvermittlungssystem Nordrhrein-Westfalen (DVS), the state telecommunication system, began in 1972. At that time, the International Organization for Standardization (ISO) Open Systems Interconnection (OSI) Reference Model had not yet been defined.

Landesamtfor Datenverarbeitungund Statistik Nordrhein-Westfalen, Postfach 1105, 4000 DOsseldoffI, FRG

Consequently, the system's structure and communication protocols had to be developed and implemented by the LDS. The DVS is based on a network using packet-switching techniques (layers 1, 2 and 3), chosen for the following reasons: • end-user connections to the DVS had to be on an on-line basis only; • the physical line had to be capable of handling connections for various partners simultaneously; • the data network had to accommodate connections between partners with different line capacities. A packet-switching network was set up, based on three communication controllers and Deutsche 8undespost leased lines. Since mid 1980, the German P-l-I- has offered an X.25 packet-switching data network (DATEX-P), and this service is also used as much as possible. To provide user services, higher layer protocols were developed by the LDS. Some of these protocols have been adapted as German prestandards: Einheitliche HOhere Kommunikations Protokolle (EHKP), i.e. Common Higher Communications Protocol (see Reference 2 for a detailed description). EHKP is implemented in more than a thousand DP systems, e.g. the hosts in the interactive videotex system (Bildschirmtext-daten-bank-rechner). Today, DVS protocols and software

0140-3664/89/0301 67-04 $03.00 © 1989 Butterworth & Co (Publishers) Ltd vol 12 no 3 june 1989

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NRW State DP-centre (LDVZ) Databases Geology JURIS DIMDI FI Z - T e c h n i k GENIOS STN data-star Bertelsmann

Ecology/ forest a f f a i r s Education

Civil s u r v e y i n g Statistical offices

Finance, c o n s t r u c t i o n , trade/industrial inspection

Federal Statist. Office Statist. Offices of Federal States

Civil s u r v e y i n g , agriculture

Justice

Other s u b s c r i b e r s

Water and waste affairs

Universities Local authorities Federal press office

NRW parliament

WFA

Finance DP-centre

LIS

GGRZ Koln GGRZ Hagen

Figure 1. Data communication system for the state of Nordrhein-Westfalen (NRW). GGRZ: Gemeinsames Gebietsrechenzentrum (Common Regional Computing Centre); LIS: Landesamt fgr Immissionsschutz (Pollution Research and Inspection Office); WFA: WohnungsbaufOrderungsanstalt (Housing Promotion DP Centre) modules are in use not only within the NRW state administration (see Figure 1), but also in: • communications systems of state and federal statistical offices; • local authorities, e.g. DCisseldorf, Stuttgart, Steinfurt; • the communications system of the largest private German bank, the Deutsche Bank; • the JURIS database (the main German legal information database based at SaarbrCicken) and in DIMDI (the medical information/ documentation database, based at KOln); • the Hochschulinformationsystem GmbH (HIS) (universities' information system) based at Hannover; • the Universities of D~isseldorf and WCirzburg; • the Federal Press Office in Bonn. DVS services As a result of both the project's

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starting date and user demands, the following application sen/ices have been designed, and are currently offered: • file transfer (including Remote Job Entry (RJE) and remote printing); • low level interactive processing (communications between an application and the user at a terminal); • network management functions; • testing facilities; • a mailbox service. The functions of Layers 5, 6 and 7 are combined in one software module called the DVS-Dienstleistungs prozess (DVS-Application Process). File transfer The DVS file transfer process is available on every system shown in Figure 1. The protocol is concerned with the transfer, access and management of files to and from

remote systems, including the RJE and remote printing functions. The transfer of multiple types of files is provided, as are checkpointing and restart procedures. In addition, there are batch and interactive user interfaces, and data security and privacy features are integrated into the system 3. Low level interactive processing (dialogue protocol) In the DVS a dialogue protocol for line-oriented interactive processing with simple functions on Layers 5 and 6 is in operation. The DVS dialogue protocol also supports full screenoriented applications, as long as the applications handle fixed-field definitions. These screens have to be defined and stored in the endsystems in advance. This type of communication has proved to be highly advantageous as it offers full screen support with a minimum data transfer charge.

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Network management functions A communication system covering a large number of applications and using many different DP systems (such as that shown in Figure 1) cannot be kept in operation only by providing protocols and application processes. The protocol implementations have to be complemented by DP-aided management functions and test procedures, both of which are provided by the DVS. Test centre A test centre for the DVS was established by 1981, enabling DP-aided tests of services, protocols and interfaces. Since 1985 the centre has been used for the initial testing of implementations of the ISO transport protocol. In addition, tests have been carried out with the GMD in Darmstadt and the UK National Computing Centre (NCC) in Manchester. In the meantime, OSl Layer 4 software products provided by the manufacturers IBM, Tandem, Digital and Nixdorf have also been tested. Mailbox service The LDS provides a mailbox system that can be accessed and handled from each DP system connected to the DVS. There are plans to enhance the DVS mailbox using a Consultative Committee on International Telephone and Telegraph (CCITT) X.400 system in 1989.

SERVICES U N D E R PREPARATION

The services described above are currently in operation, and have been well accepted by users within the administration. However, additional requirements have been identified within the state administration, and one additional service in particular has become available within the last six m o n t h s - - t h e Virtual Terminal Protocol (VTP). VTP implementation From the outset of this project, the ambitious goal existed of enabling

vol 12 no 3 june 1989

access from any terminal equipment to any DP equipment. During the course of this project, several proposals for universal terminals were made by other institutions4,s, particularly by different university research projects 6' 7. The implementations, however, have covered only the simple class (line mode). Starting with simple applications, e.g. RJE, the standardization committees worked out a basis for a wide range of applications 8. In particular, in Layer 6 a common data presentation model has been proposed. In the German prestandard Common Higher Communication Protocol (CHCP)-62, the concept of the Presentation-Image (PI) has been laid down. The PI is the view of the data structure which application entities want to refer to in their dialogue, along with a set of actions performed on this data structure. The PI is therefore the description of the current state of the communication as seen by the user processes. According to this view, a process does not see its communication partner but its image in the presentation layer. Communication between the image and the Layer 7 process takes place via the service interface of Layer 6, and communication between the two copies of the PI takes place via the Level 6 protocol data units. This communication via PIs has been described in detail in the CHCP Layer 6 9, where the Structure Elements (SE) and the protocol-dataunits have also been defined. Using that model, a protocol has been developed for the connection of the interactive videotex-com munication switching system (BildschirmtextVermittlungsrechner) to the computers of the extemal data suppliers (i.e. databases). The specification of the VTP, and the interfaces between a PI and the dialogue subsystems in two DP systems (the IBM system with MVS/XA, and the Siemens system with BS200), have been defined by the LDS1°. In addition to the two mainframes, the VTP is also being implemented on Unix machines. The implementation is divided into two parts, the central (VZ) and local (VL)

parts, each containing three layers: e Layer 7 - - the dialogue application as the interface to the subsystem or terminal control program; e Layer 6 - - the PI consisting of the SEs for the dialogue application (see Figure 2); 5 - - the ISO session e Layer protocol. To develop the facilities of the two dialogue subsystems mentioned above, it was necessary to define additional protocol data units, activity start

acknowledge, activity interrupt acknowledge, and activity resume acknowledge. It has been decided not to implement the awkward concatenation, but more than one activity within each session will be supported. The three layer entities will take the form of one program consisting of well separated modules. As there are many Unix machines participating in the computer network, many users will then have access to both types of central processors, i.e. IBM MVX/XA and Siemens BS2000, with either the 3270 or 9750 terminal interfaces. Figure 2 shows the PI structure and SE-type definitions.

CONCLUSION

As a result of the early start of the DVS system project, the computer network does not use standardized protocols; they are, however, functional equivalents to those of the ISO OSI Reference Model. In future years, some changes will be made to the different layers, because DP suppliers will offer products based on ISO standards or CCITT recommendations. The necessary changes can be carried out without disrupting services to users. It is expected that the application processes will be used for many years to come, as they are well proven, and are incorporated into accounting and securiL-y routines. In summary, the DVS is a ~ computer network using national prestandards; the architecture is that of an open .communications system.

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Parameters of terminal session Data transfer function VL-I~VZ State of terminal Control

Cursor Command to local VT-process VZ-~VZ Terminal control Data

ROOT

Presentation area

Presentation description 1

Window 0 i

I I

( Format mode)

i Presentation description j

I

I Presentation description n l Data

Logical line 0 Window s

~ Presentation description Presentation description

[

I

(Line mode) i

i Logical line u Data Presentation description ] System line

Presentation description

k

Presentation description m Identification card reader P-key 0 Programmable keys -I "

I Download font

P-key q Character 0

1 ,

Character p Field mark 0

Marking

I ]

Field mark r

REFERENCES 1 Benker, A 'Stand der Datenverarbeitung im Landesbereich unter Ber~cksichtigung der gesetzlichen Entwicklung und der besonderen Aufgabenstellung des LDS' AKD Aktuell Ausgabe 10 special (1987) pp 12-15 2 K6hlet, W 'Common data communications protocols in the FRG' Comput. Commun. Vol 6 No 6 (December 1983) pp 283-290 3 KOhler, W 'Schutzmassnahmen in Offenen Kommunikationssystemen' Proc. Online 86 Hamburg, FRG (1986) 4 Virtual Terminal Service (ISO DIS 9040 and 9041) ISO, Geneva,

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1 t

Figure 2. Presentation Image (PI) Structure Elements (SE) of the DVS Virtual Terminal Parameters of terminal session: describes common parameters defining the minimal presentation environment Control: points to SEs defining the cursor position plus commands from VL to VZ, and vice versa. Presentation area: connects a sequence of windows. System line: describes a system line. Identification card, reader: contains data being read by an id-card reader. Command VL to VZ: points to SEs defining data transfer function and terminal state. Data transfer function: contains requested transfer function and echoed sequence number. State of terminal: describes the state of local data terminal equipment Cursor: contains cursor position at the time of data transfer request plus terminal output time. Command VZ to VL: points to SEs defining the command to local VT process and terminal control Command: contains the command to local VT process and the sequence number to be echped. Control of terminal: contains terminal control information. Presentation description: describes the manner of related data presentation. Data: contains data. Programmable keys: points to a sequence of SE-defining programmable keys. P-Key: contains p-key assignment Download font" points to a sequence of SEs defining download characters. Character: defines typographic definition of a character. Marking: points to a sequence of SEs defining field marks. Field mark: is a field mark. Window: describes the presentation of an area on the local device (e.g. terminal). It contains a sequence of dependent SEs describing data and its presentation. The only valid dependent SEs are 'data" and 'presentation description'. Logical line: describes the attributes of presentation and contents of a logical line

Switzerland (1986) 5 Basic Class Virtual Terminal-Generic Virtual Terminal: Service Description and Protocol Definition ECMA-87/-88 standard (1983) 6 Black, W 'Session on fu/Iscreen services' CompuL Networks & ISDN Syst. Vol 13 (1987) pp 225 7 Gilmore, B 'A user view of virtual terminal standardization' Cornput. Networks & ISDN Syst. Vol 13 (1987) pp 229-233 8 Melendez, W A and Petersen, E L 'The upper layer of the ISO/OSI Reference Model (Part 1)' CompuL Stand. Interfaces Vol 5 No 1 (1986) pp 13-46 9 Einheitliche HOhere Kommunikationsprotokelle Ebene 5 und 6 Vieweg-Verlag, FRG (1983)

10 Virtual Terminal Protocol LDS internal report, D(Jsseldorf, FRG (1987) Wilfried Kohler studied physics and physical chemistry at the University of Munich, FRG, and graduated in 7958. He was involved in research at the Technical University of Munich until 1966, when he moved to the laboratories of the Atomic Energy Agency in Austria. Since 1971 Dr KOhler has been at the LDS NordrheinWestfalen, engaged in the development of communication protocols. He is currently interested in using OSI application protocols in public administration projects.

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