Principal Investigator Eytan Modiano
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 dominant technology 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. Our research in the area of optical networks include survivable network design, access network architecture, and mechanisms for optical bypass of the electronic layers.
Mechanisms for optical bypass: While WDM systems are likely to meet future transport demands, electronically processing all of the 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 intermediate 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. Our research in this area is focused on developing mechanisms for providing optical bypass to the electronic layer thereby reducing the size and cost of electronic switches and routers in the network. These mechanisms include traffic grooming of low rate streams, logical topology reconfiguration, and optical flow switching.
Cross-Layer Survivability: Modern communication networks are constructed using a layered approach, with one or more electronic layers (e.g., IP, ATM, SONET) built on top of an optical fiber network. This multitude of layers is used in order to simplify network design and operations and to enable efficient sharing of network resources. However, this layering also gives rise to certain inefficiencies and interoperability issues. Networks often rely on the electronic layers to provide most protection and restoration services. However, in a layered network, the protection mechanisms provided at the electronic layer may not be robust in the face of failures in the underlying optical layer. For example, SONET networks typically provide protection against single link failures using a ring network architecture, and protection in general “mesh” networks (e.g., ATM, WDM) is typically provided using disjoint paths. However, even electronic topologies that are designed to be tolerant of single link failures, once they are embedded on the physical (e.g., fiber) topology, may no longer be survivable to single physical (fiber) link failures. This is because the failure of a single fiber link can lead to the failure of multiple links in the electronic topology, which may subsequently leave the electronic topology disconnected. Thus, network survivability mechanisms often cannot provide their claimed level of protection and restoration, when embedded on a physical topology. The goal of this project is to develop a fundamental theory for understanding cross-layer survivability, and mechanisms for providing survivability in layered networks.