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过去几年中,LANt WAN中出现了很多技术发展成果,包括带宽、服务质量(QoS)、组播和可用性。在LAN中,以太网成为了占优势地位的技术;这不仅是由于它很简单、具有成本优势而且普遍存在,而且还由于它能够逐渐提高速度。在过去4年中,整个行业从共享的10-Mbps发展到了交换100 Mbps和交换1Gbps,则在则达到了10Gbps。因此,LAN网络管理员增加了网络容量,以支持越来越多的公司业务操作。在WAN中,服务供应商采用密波分复用(DWDM)等技术来扩展他们的长途网络,因此能够在他们现有的光纤基础设施上承载更多流量。这使服务供应商能够更加经济高效地利用他们在光纤基础设施中的投资。 但是,相比之下,城域网(MAN)直到现在还很沉寂。城域服务供应商大都依赖他们的同步光网络(SONE)基础设施来提供数据业务。尽管人们很了解SONET而且它也在如期运行,但是它不完全适用于数据业务。随着WAN和LAN对带宽的要求不断提高,我们有必要使LAN和WAN的容量与MAN中的传输速度相适应。
Over the past few years, there have been many technological developments in LANt WAN, including bandwidth, Quality of Service (QoS), multicast, and availability. Ethernet has become a dominant technology in LANs not only because it is simple, cost-effective and ubiquitous, but also because of its ability to progressively increase speed. Over the past four years, the entire industry has evolved from shared 10-Mbps to 100 Mbps and 1 Gbps for exchange, at 10 Gbps. As a result, LAN network managers have increased network capacity to support more and more corporate business operations. In the WAN, service providers expand their long haul networks with technologies such as dense wavelength division multiplexing (DWDM), enabling them to carry more traffic on their existing fiber infrastructure. This enables service providers to capitalize on their investment in fiber infrastructure more cost-effectively. However, in contrast, the MAN remains silent. Metro service providers rely heavily on their Sone infrastructure for data services. Although people are well aware of SONET and it is also running on schedule, it does not fully apply to data services. As bandwidth requirements for WANs and LANs continue to increase, it is necessary that we adapt LAN and WAN capacity to the transmission speed in MAN.