No other network in the world can compare to the reliability of the U.S. switched network. (Granted, a handful of disasters have disrupted PSTN services in specific regions, but these are the exceptions, not the rule.) Such reliability, however, comes at a high price: The cost of the switched network, particularly recurring (per-minute) charges, is the highest in the world. Regional toll and international calling using the PSTN are the most highly reg- ulated switched network services. This means high regulatory fees in addi- tion to recurring usage charges. But VoIP greatly reduces and may eliminate these types of charges.
The PSTN-VoIP baseline
The quality of service and high performance of the switched network have rarely been in question in the past fifty years. It is only natural that this qual- ity, which we’ve come to accept and expect, would be considered a baseline, or standard, that VoIP needs to live up to.
Living up to the quality standards of the PSTN presents a problem for VoIP. Remember that VoIP is unregulated, which means it has no enforceable qual- ity standards. Quite frankly, VoIP can’t meet the level of quality set by the PSTN in each and every network design, and therefore VoIP is not for every- body. This will change as VoIP replaces the traditional telephony services and customers demand acceptable quality standards.
As it is now, VoIP runs best when implemented on a private, dedicated net- work. With this in place, any company can utilize any of the other transports to place and receive telephony calls at low or no cost. (The dedicated network options are covered in detail in Chapter 7.) In this chapter, I clarify the three switched transports (POTS, ISDN, and DSL) that may be used to deliver rea- sonably good quality VoIP to the consumer market, to smaller companies, and to those in the home seeking to connect through their company’s larger corporate network.
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