Mechanisms for Providing Optical Bypass in WDM-based Networks

在过去的十年里，通信网络的使用和能力的增长改变了我们的生活和工作方式。随着我们进一步进入信息时代，对网络的依赖将会增加。随着数据流量的预期爆炸性增长，网络在传输和处理要求方面都将变得紧张。波分复用(WDM)正在成为主干网和接入网的主导技术。有了WDM，通过允许在多个波长(信道)上同时传输，光纤的容量显著增加，每个波长(信道)都以最大电子速率运行。目前正在部署40到80个波长的系统用于点对点传输。每根光纤有数十个波长，每个波长的传输速率高达10Gbps，可以实现接近每秒1万亿比特的容量。虽然这些WDM系统很可能满足未来的传输需求，但在网络节点以电子方式处理所有这些流量将是一个重大的瓶颈。幸运的是，没有必要对进入和离开每个节点的所有流量进行电子处理。例如，通过某个节点的大部分流量既不是从该节点发出的，也不是发往该节点的。为了减少必须在中间节点进行电子处理的业务量，未来的WDM系统将采用WDM分插复用器(WADM)和交叉连接，允许在节点分出和电子处理每个波长，或者光学地绕过节点的电子设备。该项目将开发为电子层提供光学旁路的机制，从而减少网络中电子交换机和路由器的尺寸和成本。本课程将探讨多种技术，每种技术都适用于不同的交通场景。对于低速率流业务的情况，将开发疏导算法来选择性地将多个低速率业务流复用到波长上，从而使每个节点必须处理的波长数量最小；对于突发分组业务，将开发拓扑重构算法来通过动态负载均衡来减少电子交换机和路由器的负载。最后，对于大型数据传输，将开发使用全光端到端连接绕过网络中所有电子设备的光流交换协议。上述机制的结合将降低电子交换机和路由器的尺寸、成本和复杂性，并将导致下一代互联网(NGI)所能支持的流量容量急剧增加。

Over the past decade the growth in the use and capabilities of communication networks has transformed the way we live and work. As we progress further into the information age, the reliance on networking will increase. With the expected explosive growth in data traffic, networks will be strained in terms of both transport and processing requirements. Wavelength Division Multiplexing (WDM) is emerging as a dominanttechnology for use in backbone and access networks. With WDM, the capacity of a fiber is significantly increased by allowing simultaneous transmission on multiple wavelengths (channels), each operating at the maximum electronic rate. Systems with between 40 and 80 wavelengths are presently being deployed for point-to-point transmission. With tens of wavelengths per fiber and transmission rates of up to 10 Gbps per wavelength, capacities that approach a Tera-bit per second can be achieved. While these WDM systems are likely to meet future transport demands, electronically processing all of this traffic at network nodes will present a significant bottleneck. Fortunately, it is not necessary to electronically process all traffic entering and leaving each node. For example, much of the traffic passing through a node is neither sourced at that node nor destined to that node. To reduce the amount of traffic that must be electronically processed at ntermediate nodes, future WDM systems will employ WDM Add/Drop multiplexers (WADMs) and cross-connects, that allow each wavelength to either be dropped and electronically processed at the node or to optically bypass the node's electronics. This project will develop mechanisms for providing optical bypass to the electronic layer thereby reducing the size and cost of electronic switches and routers in the network. A number of techniques will be explored, each of which is appropriate for different traffic scenarios. For the case of low rate stream traffic, grooming algorithms will be developed to selectively multiplex multiple low rate traffic streams onto wavelengths such that the number of wavelengths that must be processed at each node is minimized.For bursty packet traffic, topology reconfiguration algorithms will be developed to reduce the load on the electronic switches and routers via dynamic load balancing. Lastly, for large data transfers, Optical Flow Switching protocols that bypass all of the electronics in the network using all-optical end-to-end connections will be developed. The combination of the above mechanisms will reduce the size, cost and complexity of electronic switches and routers and will lead to a dramatic increase in the traffic capacity that can besupported by the Next Generation Internet (NGI).