This preview shows page 1. Sign up to view the full content.
Unformatted text preview: fairly static,
voice-oriented environment. Provisioning of the DACS, toll and access tandem
switches, and trunks is cumbersome but acceptable, as a result of fairly consistent
voice traffic patterns.
During the late 1980s and early 1990s, however, the rapid growth of distributed
processing and the Internet changed everything. Dial Internet access devoured
PSTN circuits with unexpected call duration times and resulted in diminished
quality of service (QoS), as voice users experienced “fast busies.” The avalanche of
Internet users forced carriers to invest in additional PSTN capacity, a costly
exercise—given that large circuit switches cost between $1 and $3 million and
DACSs between $100,000 and $250,000 for traffic that was providing little if any
In addition, the bursty characteristics and bandwidth demands (DS–1 to DS–3)
of data transmission were not well suited to the circuit-switched nature of the
PSTN and required few of its value-added voice features. Packet-switched
networks could accommodate the rapid growth and handle the bursty
characteristics of data applications more efficiently than the PSTN’s fixed 64–
kbps architecture. Carriers quickly concentrated their efforts on data-centric
architectures and constructed or expanded frame relay, ATM, and IP networks,
most of which rely on ATM as the core technology, in the underlying backbone of
the network. The specialization of voice and data or packet networks has resulted
in carriers supporting a large number of overlay networks (see Figure 1).
Figure 1. PSTN Architecture Web ProForum Tutorials
http://www.iec.org Copyright ©
The International Engineering Consortium 3/14 British Telecommunications PLC, for example, has no fewer than 17 overlay
networks, each of which requires separate network management and back-office
systems and support, and each of which has varied technical standards and
The explosive growth of data traffic also forced carriers to expand their data
network infrastructures constantly. The growth has been so rapid that companies
such as MCIWorldCom experience annual data backbone growth rates of roughly
800 percent, while vo...
View Full Document
This note was uploaded on 10/15/2011 for the course ECON 1102 taught by Professor Jahis during the Spring '09 term at University of Minnesota Crookston.
- Spring '09