Special Report: Next Generation Internet Applications
Replacement of infrastructure technologies causes some network components to be displaced from the network. The need for backward compatibility with remaining equipment and the need for continuing support of older services force functions previously provided by displaced components to appear as functions within the new equipment that displaced them. Many times communications standards developed within one service cycle persist in subsequent cycles because the standards provide legacy support for mature services or because the standards continue to perform useful functions within a new service. For example, Signaling System 7 (SS7) first appeared within the telephone network as an enhancement to the telephone routing and voice-oriented service delivery. SS7 continues to grow in scope by providing the control plane for new Internet-related services like Integrated Services Digital Network (ISDN), Digital Subscriber Line (DSL), fiber-in-the- loop, and voice-over-IP services.
Therefore, new service cycles replace obsolete equipment with more sophisticated higher capacity equipment. New equipment often provides legacy support for older services and frequently employs standards adopted during an earlier service cycle. The rapid growth in data-oriented services defines the prevailing Internet services cycle. Rapid data service growth challenges the capacity of monochromatic fiber and electronic switching. It is tipping the financial scale from telephony-based circuit switching to dataoriented packet switching. Data services growth is driving the introduction of photonic equipment throughout the communications infrastructure. The Internet services cycle is creating a new set of technology transitions within the infrastructure. Most obvious among the transitions is the rapid conversion from copper to fiber optic cable. Fiber optic cables are the foundational technology for data service growth. Fiber optic cable provides greater transmission capacity and superior transmission quality at lower cost than the equivalent copper cable. Enterprises frequently create high capacity campus area and metropolitan area networks using only fiber optic cable.
3.1 Emergence of Ethernet Network Access Services Ethernet, in its many forms, dominates enterprise networks. Enterprise networks consist largely of local area networks (LANs), campus area networks, and metropolitan area networks (MANs). LANs are almost uniformly 10 Mbps or 100 Mbps (10/100) Ethernet systems operating over twisted-pair copper or fiber optic cable. In most cases, enterprises lease the wide area portions of their networks from the public common carriers by subscribing to ATM, frame relay, or dedicated line services (T1, T3, etc.).
Gigabit (1 Gbps) Ethernet is becoming popular as an enterprise communications backbone technology. As mass production lowers the cost, Gigabit Ethernet will eventually trickle down to the desktop. Ten Gigabit (10 Gbps) Ethernet will soon be appearing within the enterprise networks, primarily as a backbone communications protocol. Ethernet will, for the foreseeable future, be popular as a communications protocol operating along the periphery of high capacity wide area networks. It is only natural that service providers are beginning to offer 10 Mbps and 100 Mbps Ethernet access services, referred to by Qwest Communications as "transparent LAN services." Transparent LAN services acknowledge the prevalence of Ethernet as the dominant enterprise network technology. Ethernet access services relieve the customer of the complexity of wide-area network (WAN) router management.
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