Optical communications – Multiplex – Optical switching
Reexamination Certificate
2000-05-30
2004-10-26
Chan, Jason (Department: 2633)
Optical communications
Multiplex
Optical switching
C398S051000
Reexamination Certificate
active
06810211
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates generally to optical network systems and, more particularly, to all-optical packet-switched routers. Even more particularly, the present invention relates to an asymmetric WDM all-Optical packet-switched router architecture and method for generating the same.
BACKGROUND OF THE INVENTION
One of the major problems in the design of all-optical packet-switching routers is reducing the overall number of components in the router, and thus reducing the number of components a signal must pass through, without effecting the teletraffic performance of the network. The number of router components required is imposed in large part by the degree of blocking probability desired. Blocking occurs when two or more competing packets at the input of a router are destined for the same output. Buffering, deflection routing, wavelength translation and link dimensioning are some of the techniques that can be used to resolve data packet conflict.
Router teletraffic performance, and the optimization of the number of components needed in a router, are usually analyzed assuming an isolated node. Furthermore, a uniform distribution is typically assumed to assign the outlet destinations of incoming data packets. The consequences of these assumptions are that router architectures require balanced wavelength conversion capability and equal buffer depths for each outlet. These assumptions thus result in a greater than necessary number of components in current WDM routers.
An optical WDM router architecture designed using the assumptions discussed above typically employs tunable wavelength conversion and symmetric optical buffering. These symmetric WDM router architectures are not designed to optimize the number of components used to solve contentions between data packets. Due to a typical optical network's topology, packets in current WDM routers may generate traffic bottlenecks produced by a tendency of the routing scheme to send packets with different destinations along preferred paths. This effect increases the traffic load, and hence the probability of blocking at the output links of specific routers, in the network. A large buffer depth, or an increase in the number of fibers per link, is therefore needed to reduce the blocking probability.
However, typical network traffic behavior is not uniform (symmetric). Asymmetric wavelength conversion capabilities and asymmetric buffering capacity more closely follow network traffic patterns and can more efficiently solve contentions. Isolated analysis based on a single network node cannot yield an optimized router architecture. An integrated analysis that considers the network topology, routing scheme, dynamic traffic distribution and multiplexing gain of the routers in a network in a single optimization module is needed to obtain an optimum all-optical router architecture and network design. Sharing of components, such as output buffers, can also reduce the number of components in a router to a preferred level. The basic idea of integrated analysis is to simultaneously optimize decision variables of different functions that have traditionally been optimized in an isolated way.
SUMMARY OF THE INVENTION
Therefore, a need exists for an asymmetric WDM all-optical packet-switched router, with or without shared buffers, that can maintain performance comparable to that of current optical routers, with a reduced number of components as compared to current optical routers.
A further need exists for a method for determining a preferred all-optical packet-switched router architecture that can analyze the teletraffic performance and optimization of a network over multiple nodes.
A still further need exists for a method for generating a preferred all-optical packet-switched router architecture that does not assume a uniform distribution in assigning the outlet destinations of incoming data packets.
An even further need exists for a method for optimizing optical router architectures that can significantly reduce the number of components required to route data packets in a manner comparable to present all-optical packet-switched routers.
Still further, a need exists for a method for performing an integrated analysis that considers network topology, routing scheme, dynamic traffic distribution and router multiplexing gain within a single optimization model to determine an optimum all-optical router architecture for a given network design.
Even further, a need exists for a method for determining a preferred WDM all-optical packet-switched router architecture using an integrated analysis that simultaneously optimizes decision variables of different functions that have traditionally been optimized in an isolated way.
The present invention provides a preferred WDM all-optical packet-switched router architecture, with or without shared buffers, and a method for determining the same that substantially eliminate or reduce the disadvantages and problems associated with previously developed all-optical packet-switched routers and methods for optimizing router component count and router placement in a network.
More specifically, the present invention provides a preferred WDM all-optical packet-switched router architecture, with or without shared buffers, and an integrated analysis method for determining said architecture. The method of the present invention includes the steps of simulating, with a network simulator, the operation of a desired network topology having at least one baseline router, establishing a steady state in the network simulation, applying a router and network dimensioning algorithm to the desired network topology for a predetermined number of clock cycles, and determining the preferred network router architecture based on the predetermined number of clock cycles. The baseline router used in the method of this invention can be a WDM all-optical packet-switched router, and the preferred network router architecture can be a WDM all-optical packet-switched router architecture with or without shared buffers.
One embodiment of the preferred router architecture of this invention comprises: at least one input fiber for receiving one or more optical data packets; a plurality of input demultiplexers for demultiplexing the data packets based on wavelength; an optical-to-electric converter associated with the output of each input demultiplexer for converting header information from each of the data packets into electric form; a control unit for processing the header information and generating control signals to control data packet routing through the router architecture; a space switch block for routing each data packet based on a current output status; a wavelength conversion module for assigning a different internal wavelength to data packets selected for conversion based on their current output status; a secondary space switch block for routing the wavelength converted data packets based on their current output status; a buffer (which can be shared), for applying a preset level of delay to data packets selected for delay (by the space switch block and the secondary space switch block) based on their current output status; a secondary demultiplexer associated with the output of the buffer for demultiplexing data packets selected for delay; a delay space switch block for routing the delayed data packets based on their current output status; and at least one output fiber for outputting the data packets from the router architecture.
The embodiment discussed above can be a WDM switched router architecture, and the one or more input fibers and at least one output fiber can be WDM fibers.
A technical advantage of the asymmetric WDM all-optical packet-switched router of the present invention is the ability to maintain performance comparable to that of current optical routers using a reduced number of components.
Another technical advantage of the method for determining a preferred asymmetric WDM all-optical packet-switched router of this invention is the ability to analyze the teletraffic performance and optimizatio
Alcatel
Chan Jason
Gray Cary Ware & Freidenrich
Li Shi K.
Sewell V. Lawrence
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