PDF of this tutorialCertainly, broadband solutions—primarily DSL and cable—are making an impression on customer choice for Internet access, and their impact will only grow over time. However, growth in new subscribers utilizing PSTN dial-up as their Internet access technology of choice is continuing as well and is not forecast to peak until 2005 (see Figure 1). It will take years for broadband to begin supplying relief to the PSTN from Internet access.
Figure 1. Access Technology Evolution
Equally concerning for the PSTN, call hold times for Internet access are increasing along with the number of dial-up users. Actual usage data indicates that average Internet session length increased 16 percent (55 to 64 minutes) in the first quarter of 2000 versus the same period in 1999. In terms of PSTN load in centum call seconds (CCS), forecasted subscriber growth multiplied by the increase in hold time nets an increase above 30 percent in data traffic over just the past year. Extrapolating an even more conservative 8 percent CAGR through 2005 predicts PSTN load increasing to more than 300 percent of what it was in 1999 (see Figure 2).
Figure 2. PSTN Impact of Increasing Hold Times
Under the weight of Internet traffic passing through the conventional Class-5 switch and tandem architecture, the PSTN collapses, leaving us with increasing busy-outs as bandwidth is consumed and the network overloaded. The dreaded “We’re sorry, all circuits are busy” message is becoming increasingly common.
