A Legacy of Innovation in Networking
This history documents key dates, decisions, and milestones in the evolution of IPSANET technology. While technical details of the underlying APL and networking systems are covered in depth elsewhere, this narrative emphasizes the development, expansion, and innovation that defined IPSANET.
Early Developments (1966–1969)
In summer 1966, I collaborated with Larry Breed and Richard Lathwell to implement a multi-user APL system on the IBM/360. By winter 1968, Ken Iverson demonstrated this system to Ian Sharp, who immediately recognized the commercial potential of a time-sharing service based on APL. Persuaded by his vision, the IPSA board acquired a computer specifically to run APL\360.
The initiative quickly gathered momentum. IPSA secured a rental agreement for an IBM 360/50 equipped with a 2703 Communications Controller—sourced from IBM Canada—and sublet space from AGT Data. With the strategic support of Harris & Partners (now part of RBC Dominion Securities), private investments totaling C$500,000 were raised to fund this project and others.
By June 1969, the IBM 360/50 was installed in the same facility as AGT’s Spectra 70. Initial telecommunications facilities used Bell Canada’s large cabinets, each outfitted with thirty 103A2 dialup modems operating local Toronto lines and foreign exchange lines for cities including Montreal, Ottawa, and Hamilton. Remote access was provided by IBM 2741 terminals or their clones, connecting via low-speed modems operating at 134.5bps.
Pioneering Time-Sharing and Global Connectivity
In late summer 1969, IPSA launched its time-sharing service by partnering with Scientific Time Sharing Corporation (STSC) in the USA. STSC facilitated the connection between the Toronto datacentre and their Washington hub using TelTech time division multiplexors and Milgo modems.
By 1971, advancements in terminal communications led IPSA to replace the IBM 2703 with a Memorex 1270, introducing support for 300bps ASCII terminals. This upgrade featured an innovative “Autospeed” capability, which automatically determined terminal speeds based on the initial character received—a feature that, despite its occasional limitations with digital multiplexors, represented a significant technical breakthrough.
When STSC inaugurated its own APL time-sharing service in 1972, an extended version of APL\360—co-developed by IPSA and STSC personnel—enabled IPSA to expand its customer base in both Canada and the United States. During this period, IPSA established links with multiple cities using a variety of technologies including digital multiplexors, frequency division multiplexors, and Trans Canada Telephone’s DataRoute system.
In 1973, IPSA expanded transatlantic service to London, utilizing a Codex 810 digital multiplexor that provided channels at 134.5bps and 150bps. However, regulatory concerns in the United Kingdom led to the temporary deactivation of a key messaging command (APL\360’s )MSG), highlighting early challenges in balancing technical capability with public policy.
Advancements and Network Modernization (1975–1985)
The mid-1970s marked a period of intense network evolution. In September 1975, IPSA upgraded its hardware by replacing several Memorex 1270 terminal controllers with a more versatile IBM 3705 Communication Controller. This new configuration optimized channel address allocation, enabling far greater terminal connectivity and providing dynamic support for users across multiple time zones.
Simultaneously, development on what would become IPSANET began in early 1975. With key contributions from Michael Harbinson and his team at Intersystems BV in Amsterdam, a prototype system emerged using a Computer Automation Inc Alpha LSI-2/20. By 1976, software enhancements—such as the introduction of the Harbinson protocol—allowed the system to support multiple network links and handle nearly 200 network calls concurrently. The network’s reliability steadily improved as logging and remote load support were added, setting the stage for robust, global connectivity.
Throughout the late 1970s and into the early 1980s, IPSA continued to innovate with specialized protocols, flexible routing, and integration with emerging technologies like X.25 and SDLC/HDLC. Upgrades such as the Macrodata BV Universal Modem Multiplexor (UMM) and later refinements with Intel chips further solidified the network’s stability, even as IPSA expanded services across North America, Europe, and beyond.
The Transition to Modern Networking (1986–Early 1990s)
By 1985, design work on the Beta node—an IPSA initiative to modernize the network using IBM PC-AT technology—began to take shape. Installation started in 1987, marking the gradual transition from older Alpha systems to newer, more flexible architectures. Innovations like the Network Shared Variable Processor (NSVP) emerged, enabling seamless variable sharing between systems and extending email and file transfer capabilities.
As the network matured, IPSANET’s software evolved to embrace an all-virtual call scheme. This shift eliminated obsolete routing information and allowed dynamic, independent call routing—an essential upgrade in the face of rapidly expanding network demands. By 1982, IPSANET encompassed 143 links and 131 nodes, and by the early 1990s, the network had peaked with over 300 nodes.
A Lasting Impact
The evolution of IPSANET is a testament to early visionaries who foresaw the potential of time-sharing and digital communication networks. Its technological innovations laid the groundwork for the global, interconnected systems we rely on today. From humble beginnings with APL systems on IBM/360 to pioneering transatlantic links and advanced network protocols, IPSANET’s history reflects a remarkable journey of technological ingenuity and adaptability.