ISDN: Where did it go wrong?

The last couple of newsletters discussed some of the background surrounding ISDN.  Today, we’ll discuss why ISDN didn’t do well in the market. The motivation for this discussion is to drive a better understanding of why some technologies don’t live up to their hype.

It’s possible to say that ISDN was at least as star-crossed as Romeo and Juliet from the start.  Except in this case, the Montagues and Capulets turned out to be packet switching and circuit switching – or the fundamental differences between data and traditional voice.

ISDN was very elegantly designed by the service provider community for the world that it understood – circuit switched voice. It also was great for a world where data communications was primarily text-based between a “dumb” terminal and intelligent centralized computers, and nobody ever attached a 10M-byte PowerPoint presentation to an e-mail message. And, for all practical purposes, at the time that ISDN was being developed Ethernet didn’t exist. The need to transport data at more than 64K bit/sec, or 128K bit/sec in extreme circumstances, simply was not part of the reigning computing paradigm.

Then the world of PCs and LANs began to emerge. At that time, a “LAN” was a now antiquated shared 10M-bit/sec connection.  However, in a few short years the norm became to ship larger and larger files, requiring higher and higher speeds and eventually dedicated LAN connections.  The applications that must be supported today were no more than a dream for the ISDN designers. 

The bottom line is that ISDN did not do well in the marketplace because the marketplace changed dramatically from when ISDN was first being discussed to when it was widely deployed – a period of roughly 10 years.  The clear learning from this is that any technology that takes too long to go from concept to production is likely to fail.