US Government Technology: "Phone Lines are not like Computers"

In a March 16 article on The Hill, “Limbaugh prompts healthcare calls, ties up House phone lines”, the US House of Representative’s Chief Administrative Officer’s spokesman, Jeff Ventura, is quoted:

Our phone system is nearing capacity . . . Unlike computers, which can be scaled to accommodate something like this in real time, phone lines are hard-wired, so you have your capacity and once the capacity is full, you’re going to get the good old-fashioned busy signal.

The funny part is that the White House’s telephone system most certainly IS a computer (i.e., a digital PBX or a small telephone switch, like a DMS10). And unlike most computers, PBXs and telephone switches are built for scaling up. They’re designed for growth!

Further, most computers cannot be scaled up without a lot of design put into the scaling.

Ventura’s attitude reflects a few common misconceptions:

  • Telephone lines aren’t computer systems.
  • Telephone lines aren’t as flexible as general computers and networks.
  • Computers can be easily added on demand, for any application.

Telephone Lines ARE Computer Systems

Every phone system available for at least ten years is a digital computer with some specialized hardware to connect to the PSTN. Many of them are based on ordinary Windows-PC-type components, like an Intel processor and a hard drive. Many of the new VoIP-based systems are just software running on a PC-based server.

Telephone lines ARE as flexible as general computers and networks

Old-school ISDN, TDM, or loop-start analog telephone lines are different than typical computing. In regular computing and networking, there are no guarantees that data will get through. But in telephony, the network is built to guarantee that after a call has started, it will continue.

In general, you have the same sort of design flexibility with telephony that you do with general computing, but you DO have to retain this imperative; i.e., you can’t drop or degrade calls after they start. VoIP systems do this through careful planning.

Computers cannot be easily added on demand, for any arbitrary application

If you want to scale up a computer system to accommodate more capacity, the system has to be carefully designed to accommodate that scaling. You can’t just add computers and connect them to the same network.

Obviously each new computer has to have the same software running on it. It needs access to the same data. And, if it’s a real application that changes that data, it has to keep the data in sync with all the other computers in the cluster. It’s no trivial task.

Fortunately, many designers build this kind of scaling into their applications. But it’s certainly not as easy as just adding more servers. Ventura is probably accustomed to computer systems that have this scalability designed into every application.