tailieunhanh - Fundamentals of Ethernet Technology

This white paper provides a brief tutorial on Ethernet – a family of standards that defines several well-established 10 Mbps networking technologies and three newer, high-speed offerings, Fast Ethernet, Gigabit Ethernet, and 10 Gigabit Ethernet. It is intended for carrier network professionals, experts in the circuitswitched technologies employed in public switched telephone networks (PSTN) but often new to Ethernet and data networking. | Fundamentals of Ethernet Technology WHITE PAPER Fundamentals of Ethernet Technology This white paper provides a brief tutorial on Ethernet - a family of standards that defines several well-established 10 Mbps networking technologies and three newer high-speed offerings Fast Ethernet Gigabit Ethernet and 10 Gigabit Ethernet. It is intended for carrier network professionals experts in the circuit-switched technologies employed in public switched telephone networks PSTN but often new to Ethernet and data networking. Why Study Ethernet Ethernet is becoming an important carrier network technology. For many years it was relegated to office LANs local area network connecting PCs servers and printers. Recent high-speed implementations however make Ethernet a viable candidate to provide new carrier-based services such as Voice over IP VoIP a technology that enables voice calls over data networks. This may one day eliminate the need for separate voice and data facilities. Metropolitan area networks MANs high-bandwidth pipes that can link company data centers over a 15 to 20 mile area Ethernet in the First Mile EFM an emerging standard that may compete with DSL and cable modems to bring voice video and data to homes The PSTN and Ethernet The PSTN and Ethernet were designed for very different purposes. The result is different technologies at least in two key areas switching techniques and network access methods. Figure 1. Circuit-Switched Network Circuit-Switching A Voice-Friendly Technology Have you ever heard a television news anchor question a distant reporter over a satellite link You probably have and it s quite likely that the moments of dead air between the question and the response made you uncomfortable. That s what latency does to conversation. Designers of the public telephone network understood this so they created circuit-switched networks to minimize it. In these networks an end-to-end circuit is established Figure 1 before a conversation begins and circuit .