In this retrospective article, Ron Angner takes us to a telco’s central office (a.k.a. telephone exchange) where we see the change in technology over the last 25 years. From floors of noisy equipment to today’s software in the cloud, network technology has transformed from the physical to the virtual.

Now You See Me, Now You Don’t – The Journey of Switching Office Technology

The first time I walked into an Electronic Switching System (ESS) office the quietness was deafening. I remember saying to myself, “Wow, this is so quiet!” Not only that, but it provided two to three times as much switching capacity as the old legacy technology. Equipment that use to take up floors of a central office was now being provided on a single floor – and sometimes less. The old legacy technology of course was the step-by-step and crossbar-switch technology.

Before I go on, let me briefly explain: network switching technology enables us to make those calls (and nowadays, texts, video, and more) that connect us to our loved ones from handset-to-handset. There used to be a lot of hardware to make that happen.

By 1991, ESS offices were a common sight. Wireline operators had already replaced most of the old mechanical switches and with it, a change in skills too. Before, switch technicians had to be mechanically inclined to keep things running smoothly. Now, the new breed of technicians had to be savvy with electronics and computers.

With electronic switching came speed in call completion and an incredible set of new services. Local service completion was always ‘somewhat fast’. Now with computers in the network, coast-to-coast calls could be completed in just milliseconds. With computer technology in the signaling systems (SS7), signaling control points (SCP) and the signaling transfer point (STP), calls could be moved about and routed in what seemed like instantaneously. Imagine a call going from coast-to-coast could receive routing information from three or four sources as it made its way across the United States.

The ‘electronics age’ of the 90s brought an entirely new set of services to both residential and business customers. Features such as speedy touch-tone dialing, voice mail, call transfer and hold amazed the consumer while toll-free numbers, VPN, SDN and other services completely changed the way businesses operated. Toll-free 800 number services, for instance, routed calls from anywhere in the country to a common point by performing a computer data base “dip” to determine routing information – in the mere flick of an eyelash.

In the late 90s a funny thing began to happen in networks – as the Internet exploded, suddenly there were little gremlins, known as packets, running about at great speeds and taking up more capacity than voice calls. This was the advent of the second transformation in switching – the introduction of Internet Protocol (IP) technology. All of a sudden voice and data could be intertwined and carried over a common platform – the IP network. Voice was being whisked around networks in packets with quality equivalent to that provided by the legacy switched network. The concept of Voice over IP (VoIP) was with us.

So walk with me now into one of the industry leading switching offices – or is it even a switching office anymore? We walk into the office and what do we see? Do we see the lineup of frames that used to make up the electronic switching system? The STP or the SCP? No, we see a series of computer-like boxes that people call “soft switches”. IP switches that are completely changing the technology landscape. Good hot, strong coffee is always available in these offices, so let’s grab a cup and talk to the tech. As we talk to some of them, they talk of Media Gateways, Media Gateway Controllers and Session Initiation Protocol (SIP). We begin to realize that they are actually software technicians – what is this world coming to?!

But it’s not just the electronics in the network that are providing major changes for consumers and businesses. With VoIP, carriers can replace the aging copper lines in the access network (from the central office to the customer premises) with shiny new fiber. Those copper lines were spec’d to carry voice frequencies from 300 - 3000 Hz. The fact that they can now also be used for broadband is amazing, but fiber is faster still and much cheaper to maintain. Many carriers have plans in place to replace the majority, if not all, of their copper plant in the next 5 – 7 years. Looking back over the years, it was almost unimaginable to think of a tiny thread of glass carrying gigabits of information. It’s a world away from when the telephone lines to homes and business were the battleship grey lines coated in lead – and that did not even keep the squirrels at bay!

As we return from the break room, I see papers spread out all over the technician’s desk. I turn to the technician to see what this is all about and he says, “This is the project plan I have been given to implement.”

In addition to the project documents, I also see lease termination agreements. In amazement, I turn to the technician and ask, “Where is everything going to go if you are moving out of this building?” With a grin on his face, he says to me, “It is going to the cloud – we are moving to the virtual world now.”

Enter network virtualization, the third transformation of switching which is just starting to take hold: the Central Office Re-architected as a Data Center (CORD). Vendors are virtualizing the functions of today’s soft switches so that they can run as software on generic computer servers. Using new technologies such as Software Defined Networking (SDN), Network Function Virtualization (NFV), and Lifecycle Service Orchestration (LSO), CORD promises to free operators from the inflexible networks and tap into the elastic, scalable, agile world of cloud computing. In this new world there’s no need for customized switching equipment. So, you ask, what is left in the central office?

Well, in spite of all the virtualization and everything else we have accomplished, there’s still a need to connect all of the lines (or fibers) from customers back to the network. The physical layer of the network is the component that will be left in what used to be called the central office. This means that you’re still going to need some technical sites, just less of them and without the huge space and power requirements of the past.

So, on our journey, we went from floors of mechanical equipment to a single floor of electronics and then to virtual elements in the cloud. Along the way, operators have reinvented their networks to add features, reduce costs and launch new services. One wonders what networks will “look” like and what they’ll be able to achieve in the next 25 years? <>

To mark Cartesian’s 25 years in the telecoms, media, and technology sector, we asked our consultants to reflect on industry topics and write about how they have changed over the last few decades. Click here to receive your copy of our anniversary eBook: 25 Years – A retrospective on innovation in the telecoms, media, and technology sector