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Internet Phone Services Simplified by Neil Anderson, Jim Doherty

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Chapter 4. Knowing Your Limits

Along with all sunshine, a little rain must fall. You need to be aware of some limitations of broadband phone services. Two major categories of limitations exist: reliability and 911 services. These are discussed in the sections that follow.

Reliability

As we discussed in Chapter 1, “Traditional Phone Systems,” the public switched telephone network (PSTN) has been designed, engineered, and reengineered to achieve the five 9s of reliability (also known as 99.999 percent uptime). In real terms, this means that, on average, the system has no more than about 5 minutes of downtime per year. For the most part, the PSTN lives up to this incredible standard.

So the obvious question is “Are broadband phone services as reliable ...

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