TRAME (TRAnsmission of MEssages)Selga, J.M. « TRAME: A Packet Switching Computer Network for Power Systems». Proceedings of CIGRE (Conference Internationale del Grandes Reseaux Electríques), Paris Session 1978, Paper 35-03, September 1978. was the name of the second computer network in the world similar to the internet to be used in an electric utility. Like the internet, the base technology was packet switching; it was developed by the electric utility ENHER in Barcelona. It was deployed by the same utility, first in Catalonia and Aragón, Spain, and later in other places. Its development started in 1974 and the first routers, called nodes at that time, were deployed by 1978.Hoffmann M.G. and Selga J.M. «Line Control Unit for a Packet Switching Network». Proceedings of MIMI. Zurich, June 1978.Selga J.M. and Xampeny J. «Flow-Adaptive Updating Procedure for Dynamic Routing. Comparative Simulation Results». Proceedings of IEEE International Conference on Communications (ICC'80), pages. 23.6.1 to 23.6.6., Seattle (WA), USA, 1980.Selga J., Rivera J., Xampeny J. «Modelos analíticos y de simulación utilizados para el diseño de la red de conmutación de mensajes de ENHER». I Symposium Nacional sobre Modelado y Simulación en la Indústría y Servicios Públicos. Sevilla., 7–9 May 1980.Selga, J.M., Rivera.J., Xampeny, J. «Red TRAME de conmutación de paquetes». Revista Novática, Vol. VII, num.37, 1981. The network was in operation until 2016 (38 years) with successive technological software and hardware updates.
Beginnings
In 1974, packet switching was a technology known only in research circles. The concept began in 1968 in association with the United States' Advanced Research Projects Agency (ARPA) research project ARPANET. The idea of applying the packet switching concept to electric utilities control communication networks first appeared in 1974 when the Swedish power utility Vattenfall started to create its TIDAS packet-switching networkJerlhagen, T. and B. Leander, B., “A Message Switching Network Designed for Data Communication and Remote Control”, Proceedings of CIGRE, Paris France, Paper 35-01, August 1974. Cegrell, T. «[A Routing Procedure for the TIDAS Message-Switching Network]». IEEE Transactions on Communications, Volume 23, Issue 6, pag. 575-585, June 1975 and was followed by the Spanish electric utility ENHER,Sánchez i Vilanova, Llorenç. L’aventura hidroelèctrica de la Ribagorçana-ENHER i la seva influència en la transformació sòcio-econòmica de l’Alta Ribagorça”, Història i Cultura de l’Alta Ribagorça-Volum I (in catalan). La Pobla de Segur: Printer: Casa Torres S.A., Dipòsit legal: L-679-1991, Edits: Associació d’Amics de l’Alta Ribagorça., 1991. . which aimed to telecontrol and automate its high-voltage power grid. For this purpose, ENHER created a specific team of people to develop both the packet-switching network and the supervisory control and data acquisition (SCADA) system, also called the telecontrol system. By 1978 the first four TRAME routers were available and by 1980, eight of them were deployed and operating.Selga, J.M., Rivera, J., Xampeny, J. (Book coordinated by A. Alabau and J. Riera) (In Spanish. Red TRAME de conmutación de paquetes (Teleinformática y redes de computadores). Barcelona: Marcombo, p. 95 to 101, First Edition: 1982. Second Edition: 1984, ISBN 84-267-0427- 1. The printed circuit boards (PCBs) controlling the communication lines were connected to a shared memory PCB allowing them to exchange data and messages. The project was developed together with its main initial application, the Telecontrol or SCADA system SICL ()Ventosa, J.; Sanchez, M.; Casals, A.; Rivera, J.; Xampeny, J. «An Integrated Station Local Control-Telecontrol System in the Scenario of an Overall Telecontrol System». IEEE Power Engineering Review, Volume PER-6, Issue:10, pages. 39 - 40, 1986 Ventosa, J.; Sanchez, M.; Casals, A.; Rivera, J.; Xampeny, J. «An Integrated Station Local Control-Telecontrol System, in the Scenario of an Overall Telecontrol System]». IEEE Transactions on Power Delivery, Volume: 1, Issue: 4, pages. 159-165, 1986 Equipo TAC de ENHER «Sistema de Telecontrol integral para redes eléctricas. Una avanzada realización española». In Spanish. Mundo Electrónico. num.110., 1981. with which initially they shared a very similar hardware. The maximum link capacity was 9600 bit/s, which in 1980 was the maximum possible on a 4 kHz wide voice channel at the time. These channels were the basic unit of the then-analog communication systems in use. By that time power utilities used either telephone calls or low speed (below 1200bit/s) dedicated links for telecontrol, typically shared among ten high-voltage electrical substations.
Services
The basic service provided by the TRAME network was SCADA or Telecontrol to automate the high-voltage power grid, thus improving operational efficiency, which was until then operated manually with telephone communication between human operators. Each TRAME router was associated with one or more remote terminal units (RTUs) of the SICL telecontrol system. It also had connected screens, and later PCs, located in electrical substations to interchange messages between them and with the Control Center located in the well-known in Barcelona. It was a kind of predecessor to today's e-mail. Later, in the 1990s, other protocols (X.25, IP) were developed to include corporate information technology (IT) terminals, company physical surveillance systems and other services. Additionally, applications and terminals were developed for the transmission of voice and video over the TRAME network.F. Álvarez-Cuevas Figueroa, M. Bertran, Oller, F., J. M. Selga, «Voice Synchronization in Packet Switching Networks». IEEE Network Magazine, Volume 7; Issue: 5, p. 20-25, September 1993 J. Dalmau and J.M.Selga «Slow-Video Network». CIGRE SC35 Colloquium in Madrid, September 1995.
Protocols
The TRAME routing system, like that of the original ARPANET, was based on the Bellman-Ford algorithm but with "split-horizon" as in the Swedish TIDAS network, but with an original improvement. This protocol allows optimal paths to be found in meshed networks for each packet to be transmitted, allowing the shared use of the same network by multiple services. In contrast, traditional circuit-switched technology used to establish dedicated circuits for each service or communication. The addressing of routers and terminals used a proprietary system with a 16-bit address; it would be the equivalent of the well-known IP (Internet Protocol) version 4 (IPv4), still in use on the internet today, which uses 32-bit addresses. It is necessary to take into account that in 1978, the IPv4 protocol did not yet exist since the IPv4 version used on the internet did not appear until 1981, and in fact, did not reach the general public until much later.
The line protocols were also proprietary and were called UCL (, 'line control unit'), which linked the routers together, and UTR (), the access protocol. They were designed to offer the highest quality of service required by the telecontrol/SCADA function in terms of data integrity and availability set by the International Electrotechnical Commission (IEC) IEC-870-5-1 and ANSI C37.1. standards, and because the protocol used at the time in corporate computer networks, HDLC (high-level data link control), did not offer enough quality for critical industrial applications.Selga, J.M. and Rivera «HDLC reliability and the FRBS method to improve it». IEEE Seventh Data Communications Symposium Mexico, 1981.Selga, Josep Maria «Contribucions al disseny i optimització de xarxes d’ordinadors» (Contributions to the design and optimization of computer networks). In Catalan. Doctoral Thesis, September 1985. Later on, other protocols like X.25 and IP were also made compatible with the aforementioned TRAME protocols. In 2000, the UTR protocol was replacedCabezas, R.;Selga, J.M.;Samitier, C. «Experience in the implementation of a Telecontrol network based on the IP technology». Proceedings of CIGRE (Conference Internationale des Grandes Reseaux Electriques) Paris Session, Paper 35-201, September 2000. by the international standard IEC 60870- 5-101/104.
Initially network flow control was based on the management of eight data priorities in head-of-the-line (HOL) waiting queues. Later and after some experimentation,Selga J., Xampeny J. «Congestion Control Method for the TRAME network. Description and Simulation Results». IEEE Proceedings of the Mediterranean Electrotechnical Conference MELECON'83. Athens(Greece), 23–25 May 1983. a flow control method based on a bit indicating route congestion and management of the gap between packets when accessing the network was adopted. This required measuring the capacity of the route bottleneck.Selga, J.M. «Optimum Control of Packet Switching Networks». Electronic Letters. Vol.19., pag. 794-795,15 September 1983. Selga, J.M. «Flow Control Method for Packet Networks». Proceedings of the 8th International Conference on Computer Communications ICCC 1986. München, p. 625-630,15-19 September 1986.Selga, J.M., Altemir, S. «Uso de redes de conmutación de paquetes en telecontrol» (In Spanish). Proceedings de les Primeres Jornades sobre Telecontrol Industrial. Escola Universitària d'Enginyeria Tècnica Industrial de Barcelona, 3–5 April 1984.Selga, J.M. «Optimización del uso de redes de conmutación de paquetes» (In Spanish). VI Congreso de Informática y Automática. Madrid., 15–18 October 1985. An end-to-end protocol was also added for some flows requiring order preservation like X.25.
Evolution
To last for 38 years, the technology had to endure intense evolution. There were essentially four TRAME generations which are summarized in the table.
Concept TRAME 1 TRAME 2 TRAME 3 TRAME + Development started 1974 1993 1998 Deployment started 1978 (4 routers in operation) 1988 1990 (fully deployed) 1995 1999 Processor Zilog Z80 Intel 80286 Intel 80386 i960CA i960RM Maximum link speed 9600bit/s 64kbit/s 2Mbit/s 10Mbit/s Hardware 16 processors sharing a common memory 16 processors sharing a common memory 16 processors sharing a common memory distributed among the 16 PCBs. A single processor with a shared multimaster 1Gbit/s bus to communicate I/O boards. Hardware developer/manufacturer ENHER/ISEL (INI) ENHER/ISEL (INI) DIMAT, S.A. DIMAT, S.A. Addressing field 14 bits · 256 routers (8 bits) · 64 terminals per router (6bits) 16 bits · 256 routers (8 bits) · 64 terminals per router (6bits) · 4 interconnected networks (2 bits) 16 bits, as in TRAME 2 16 bits, as in TRAME 2 Managed priorities 8 8 8 8 Inner link protocols UCL (proprietary) UCL improved for 64kbit/s (proprietary) UCL improved for 64kbit/s (proprietary) UCL improved for 2Mbit/s (proprietary) Access link protocols UTR (proprietary) · IPv4 (1999) · X.25 · Proprietary: UTR · International Electrotechnical Commission's IEC 60870-5-101/104 · IPv4 · X.25 · Ethernet The same as for TRAME 3 Network size evolution 1978: 4 routers 1980: 8 routers
1983: 27 routers
1987: 32 routers 1994: 50 routers 2004: 222 routers 2014: some 3000 routers (several networks) Router appearance
A description of the four generations of TRAME is provided below.
TRAME 1
The project began in 1974 and in 1978 a first network with four routers was already installed and in operation at the electric utility ENHER. In 1980, the network had eight nodes in operation (see Figure I). The hardware was based on the Zilog Z80 processor and had a multiprocessor structure with 16 processors sharing a common memory. The software was developed at ENHER's headquarters located in the well-known Casa Fuster, , 132, Barcelona, using the Z80 assembly language. Beyond 1980 the software began to be written in C programming language and an HP64000 Logic Development System emulator was used for the purpose. The hardware was produced by ISEL, an INI () company.