以太网是目前全球使用最广泛的局域网技术。它成功的原因在于,在过去２０年里,其标准一直随着网络的需求不断改进。作为ＩＰ网络的一种极具吸引力的解决方案,以太网具有下列关键特性:可扩充性;灵活的部署距离,支持从短程局域网(大约１００ｍ)到长距离城域网(４０ｋｍ以上)的各种网络应用;成本低;灵活性和互操作性;易于使用和管理。这些因素使以太网成为４种关键网络的实现技术。 Ethernet is by far the most widely used LAN technology in the world. The reason for its success is that its standards have been constantly evolving with the needs of the web over the past two decades. As an attractive solution for IP networks, Ethernet has the following key features: scalability; flexible deployment distance, from the short-range local area network (about 100m) to the long-distance metropolitan area network (40km and above) Network applications; low cost; flexibility and interoperability; easy to use and manage. These factors make Ethernet a key enabler for four key networks.