During the past three years, I had product management responsibilities for products which covered the spectrum from hardware-centered to software-centered development. In telecom, there’s been an evolution in development models as solution providers have taken a series of steps to gradually move away from hardware. However, like many technical trends, there is a long tail as the older technology goes away only gradually. In this post and others to follow, I’ll review models for voice applications at a high level and consider some steps along the way which have led to the software-oriented nirvana sought by many solution providers.
In the Nineties, voice development was often done with PCs at the center and embedded board hardware was an important component. The CPUs of the PCs ranged from models like the 386 on up to Pentium. Voice applications entailed lots of media processing, so voice boards with lots of Digital Signal Processors (DSPs) were critical to get scalable applications. The DSPs did all of the heavy lifting for the media and the CPU of the PC was freed up to support the application side for solutions such as call centers, interactive voice retrieval and fax on demand. Many of the applications developed during this time are still being used, though the actual PCs or servers may have been replaced and there may also have been some upgrades on the voice board hardware. Nonetheless, thousands of voice boards are still being sold to support these applications. On the software side, there were efforts to create industry standard Application Program Interfaces (APIs) such as S.100 from the Enterprise Computer Telephony Forum (ECTF) and T.611 from the International Telecommunications Union, but most of the boards were controlled using private APIs supplied by the board vendors.
In the model above, the boards and applications were all designed to work over the circuit-switched telephone network, which ranged from analog services (POTS or Plain Old Telephone Service) to digital approaches which began with the Integrated Systems Digital Network (ISDN) and continued with the Signaling System 7 (SS7) network overlay. The phone companies worldwide assumed that these circuit-switched networks with Time-Division Multiplexing (TDM) and the related seven layer Open Systems Interconnect (OSI) models would be the focus going forward, replacing analog networks, and would perhaps be supplemented by new OSI stacks such as the Asynchronous Transport Method (ATM).
But a revolution had already begun as alternative flatter telecom stacks based on the upstart Internet Protocol (IP) protocols were being used both for existing applications such as email and new applications like the Worldwide Web. In the telecom industry, a few companies began to explore running voice over IP networks, thus creating a new Voice over IP (VoIP) technical and business model for phone networks. In the early days (from the late Nineties to the early 2000s), VoIP was mainly used to bypass existing long distance networks to reduce long distance charges, but the range of applications for IP soon began to expand.
At first, this looked like a great opportunity for the voice board manufacturers. Now, they could add IP support to their boards or potentially just give software developers access to Ethernet ports on PC. An important new board category was created: the media gateway. These early media gateway boards allowed developers to use the existing circuit networks for most of their connections, but also tap into new IP networks where they existed. Continuing on the same API trends, board vendors extended their private APIs to support IP in addition to TDM. So now solution developers could run their solutions over both existing TDM and new IP networks, using these new hybrid boards which often could support voice, fax and tones.
In my next post, I’ll talk about how media gateways helped to kick off a new voice development model which accelerated the separation between software and hardware for voice and the new application category which became Unified Communications.
If you participated in the evolution described here, please feel free to weigh in with your comments. If you’d like to explore strategies on how to evolve your solutions, you can reach me on LinkedIn.
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