Error detection/correction and fault detection/recovery – Pulse or data error handling – Transmission facility testing
Reexamination Certificate
1999-10-29
2002-11-12
Baker, Stephen M. (Department: 2133)
Error detection/correction and fault detection/recovery
Pulse or data error handling
Transmission facility testing
C370S241000
Reexamination Certificate
active
06480977
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to monitoring of optical links and, in particular, to monitoring the traffic of an optical communications network by monitoring an optical link of the communications network.
BACKGROUND OF THE INVENTION
It is known in the prior art to passively monitor the various protocols of information traffic flow at both ends of an information carrying link within a communications system such as a synchronized optical communications network (SONET). The prior art techniques for monitoring packets formed of information containing cells include capturing the packets from an optical link as the packets were being transmitted from one point in the network to another through the link. These prior art link monitoring devices are capable of capturing packets transmitted on a link until the available memory were full.
Usually when a packet is captured, it is time stamped. An exception is a transmission method wherein the cells of the packet are segmented at one end of the optical link prior to transmission and reassembled at the other end. Here each cell of the data packet is time stamped by the link monitoring device and a linked list of the order of the captured cells is maintained in order to permit the reassembly operation.
Link monitoring devices could include optical cards for performing such operations as the actual capture of information packets and the various conversions required for a host computer to perform analysis upon the captured packets. The analysis by the link monitoring devices included procedures such as statistical analysis. Within link monitoring devices of this type the host would supply memory blocks to the optical cards for containing intercepted information.
Another kind of analysis performed by the host computer on packets received from the optical card was quality analysis. When quality analysis was performed, a stream of traffic through an optical link was monitored at multiple locations throughout the network and the results were compared. Packet corruption and packet loss could be determined using the comparison. Usually the comparison required communication between different link monitoring devices. Quality analysis could be performed in parallel with the normal flow of information through the monitored optical link. Furthermore, it could be performed without having any impact on the normal information flow.
Baseline traffic flows through different parts of the optical network were also determined using the known link monitoring devices. Current traffic flows were then compared to the determined baselines in order to ascertain the current state of the network. The routing of the network traffic flow could then be adjusted according to the current state of the network. Additionally, archives of traffic flow data were developed and the archives were used to determine network behavior and to determine and predict traffic flow trends within the network. Traffic path data and frequency of routing path changes, or network connectivity, was also studied.
SUMMARY OF THE INVENTION
A method is taught for monitoring information traffic through a traffic link transmitting first and second differing information signals each having a plurality of information layers and first and second pluralities of information packets. The method is practiced in a monitoring system having monitoring circuitry and including processor circuitry and a server operating cooperatively with the monitoring circuitry. The method includes segmenting the information packets of the first and second pluralities of information packets into information cells to provide corresponding first and second pluralities of information cells and interspersing the information cells of the first and second pluralities of information cells with each other to provide interspersed first and second information cells. The method further includes intercepting a portion of the interspersed first and second information cells to provide intercepted interspersed information cells using an interceptor coupled to the traffic link and stripping an information layer from the intercepted interspersed information cells by the monitoring circuitry to provide a remaining information signal including portions of the intercepted interspersed information cells. The intercepted interspersed information packets of at least one of the first and second pluralities of information packets within the remaining information signal are reassembled to provide a plurality of reassembled information packets by the processor circuitry. An analysis is performed on the plurality of reassembled information packets by the server.
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Apisdorf Joel
Burden Keith
Baker Stephen M.
WorldCom, Inc.
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