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目前最主要的光交换方式有:光电路交换(OCS)、光突发交换(OBS)、光分组交换(OPS)。从长远来看全光的分组交换(OPS)是发展方向,然而OPS需要光存储器,交换颗粒小以及交换节点需要精确同步,所以在短期内难以实现。光突发包交换(OBS)是电路交换向分组交换的过渡技术。OBS使用的带宽粒度介于电路交换和分组交换之间,比电路交换灵活、比光分组交换更贴近实用,但是OBS也存在着不足之处。因为缺乏光随机存储器,而且光纤延迟线只能提供有限固定的时延,不能有效对光突发进行缓存,突发丢失率较高,从而导致IP包丢失率高。目前交换领域中一个很热的研究重点是把MPLS(多协议标签交换)的概念扩展到光传送网,MPLS既具有IP的灵活的路由能力,又有ATM的面向连接的服务质量保证,将这种具有流量工程能力和虚拟专网支持能力的技术与光交换技术相结合,将传统的MPLS面向光网络进行功能扩展,不仅能以波长为粒度进行标签交换(MPLmS)、还能以数据包/分组、时分复用的时隙、光纤等为粒度进行标签交换,由此形成并提出通用多协议标签交换(GMPLS)技术。GMPLS技术结合光纤本身的超大带宽特性,从而能同时满足传统电信业务、数据业务和视频业务的需要,并为未来的新型业务提供了一个具有适应性的统一的技术平台。
Currently the most important optical switching methods are: optical circuit switching (OCS), optical burst switching (OBS), optical packet switching (OPS). In the long run, all-optical packet switching (OPS) is the direction of development. OPS, however, requires optical memory, small switching granularity, and precise synchronization of switching nodes, making it difficult to achieve in the short term. Optical Burst Packet Switching (OBS) is a transitional technology from circuit-switched to packet-switched. The bandwidth granularity used by OBS is between circuit switching and packet switching. It is more flexible than circuit switching and more practical than optical packet switching. But OBS also has some shortcomings. Because of the lack of optical random access memory, and fiber optic delay line can only provide a limited fixed delay, can not effectively buffer the optical burst, the burst loss rate is higher, resulting in high IP packet loss rate. At present, a hot research topic in the field of exchange is to extend the concept of MPLS (Multi-Protocol Label Switching) to the optical transport network. MPLS has both the flexible routing capability of IP and the connection-oriented quality of service of ATM. The combination of technology with traffic engineering capability and virtual private network support capabilities and optical switching technologies extends traditional MPLS for optical networks with the ability to perform label switching (MPLmS) at wavelength-granularity and packet / Packet, time-division multiplexed time slot, optical fiber and so on for the granularity of label exchange, which formed and proposed a universal multi-protocol label switching (GMPLS) technology. GMPLS technology combined with the ultra-wide bandwidth of the optical fiber itself to meet the needs of traditional telecom services, data services and video services at the same time and provide an adaptable and unified technology platform for new services in the future.