Why Did Broadband-ISDN Really Die?

There are positive reasons for the smooth uptake of IP, such as the easy availability of the TCP/IP stack as compared with competing proprietary data protocols, the relative simplicity of the basic Internet architecture, and the prior existence of enterprise multiprotocol routers that could be used directly as Internet routers.
Perhaps more important, though, were the problems with ATM. In the 1980s when ATM was being designed, the dominant usage mode was seen to be the multimedia successor to the phone call—human beings making videophone calls. As we saw above, interactive multimedia is the most challenging application for packet networks, requiring a complex infrastructure of signaling, terminal capability negotiation, and QoS-aware media transport. It was not until the mid-nineties that large ATM switches capable of supporting the required signaling and media adaptation came to market—too expensive and too late.

Even worse, the presumed videophone usage model for B-ISDN was highly connection-oriented, assuming relatively long holding times per call. So ATM was designed as a connection-oriented protocol with substantial call set-up and tear-down signaling required for every call to reserve resources and establish QoS across the network. This required per-call state to be held in each of the transit network switches. For comparison, millions of concurrent calls (sessions or flows) transit a modern Internet core router and that router knows nothing whatsoever about them.

It turned out that critical enabling technologies for the Internet, such as DNS, require brief, time-critical interactions for which a connection-oriented protocol is inappropriate. Even for connection-oriented applications such as file transfer, which use TCP to manage the connection, connection state is held only in the end systems, not in the network routers, which operate in a connectionless fashion. This has allowed the Internet to scale.

So in summary, ATM had too narrow a model for how end-systems would network, and backed the wrong connection-oriented solution that couldn’t scale. Because ATM was designed against a very sophisticated set of anticipated, predicted requirements, it was very complex, which led to equipment delays, expense, and difficulty in getting it to work. The world moved in a direction not anticipated by the framers of B-ISDN and it was stranded, and then discarded.

Architecture vs. Components

The Internet was put together by many people and organizations, loosely coupled through standard protocols developed by the IETF. Some of it works well, some Internet services are beta or worse. The world of the Internet is exploratory, incremental, and sometimes revolutionary and it’s an open environment where anyone can play and innovate. The libertarian ideology associated with the IETF theorizes this phenomenon. The IETF saw (and sees) itself as producing enabling technologies, not closed solutions. Each enabling technology—security protocols, signaling protocols, new transport protocols—is intended to open the door for new kinds of applications. To date, this is exactly what has occurred.
Add a note hereThe Internet model is disaggregated—the opposite of vertically integrated. Because the Internet is globally accessible and presents support for an ever-increasing set of protocols (equating to capabilities), anyone with a new service concept can write applications, distribute a free client (if a standard browser will not do), and attempt to secure a revenue stream. This creates a huge dilemma for carriers. In the Internet model, they are infrastructure providers, providing ubiquitous IP connectivity. In the classic tee-shirt slogan “IP over everything,” the carriers are meant to be the “everything.” But “everything” here is restricted to physical fiber and optical networking in the network core; copper, coax, and radio in the access network; plus an overlay of routing/forwarding and allied services such as DNS. When it comes to end-user services, whether ISP services such as e-mail and hosting; session services such as interactive multimedia, instant messaging, file transfer; or E-business services such as Amazon, eBay, e-Banking, there is no special role allocated for carriers—the Internet model says anyone can play.
Add a note hereThis thought is entirely alien to the carriers, who have long believed they were more in the services business than mere bit transporters. Carriers have always wanted to move “up the value chain” whether they were offering network-hosted value-added services or integrated solutions to their enterprise customers. As the carriers came to terms with the success of the Internet, and the collapse of Broadband ISDN, they attempted their own theorisation of the Internet. Not in the spirit of the libertarian open model of the IETF, but more akin to the vertically-integrated and closed models they were used to. They proposed to integrate
§  Add a note hereData and media transport
§  Add a note hereInteractive multimedia session management
§  Add a note hereComputer application support
Add a note hereinto one architecture where everything could be prespecified and would be guaranteed to work. And so arrived the successor to Broadband ISDN, the Next-Generation Network (NGN).
Add a note hereThe advantages of the NGN, as the carriers see it, include a well-integrated set of services that their customers will find easy to use, and a billing model that keeps their businesses alive. The disadvantage, as their critics see it, is the reappropriation of the Internet by carriers, followed by the fixing-in-concrete of a ten-year roadmap for the global Internet. The predictable consequence, they believe, will be the stifling of creativity and innovation, especially if the carriers use their NGN architecture anti-competitively, squashing third-party Service Providers, which is technically all too possible.
Add a note hereWe should be clear here: anyone offering an Internet service has to develop a service architecture. In the IETF’s view of the world, it is precisely the role of Service Providers to pick and choose from the IETF’s set of protocol components and to innovate architecturally. There is absolutely no reason why the carriers shouldn’t do their architecture on a grand scale through the NGN project if they wish. Critics may believe it’s overcomplicated, non-scalable, and ridiculously slow-to-market. If they are right, Service Providers with lighter-weight and nimbler service architectures will win in the marketplace, and the all-embracing NGN initiative will fail. “Let the market decide” is the right slogan, but the market must first of all exist, which means that the Internet’s open architecture must be preserved and not be closed down. Many carriers have significant market power and might be tempted to use it in order to preserve what they take to be their NGN lifeline against effective competition, so this is an issue for both customers and regulators. Thankfully, there are reasons to be hopeful as well as fearful.