Passive monitor for broadcast communication network
First Claim
1. A method for passively monitoring an operating data communications network, the network including a plurality of stations, the stations communicating by exchanging data and control information in accordance with a protocol, the method for monitoring comprising the steps of:
- storing information which represents an expected sequence of control information exchanged between two stations in the network;
passively detecting sequences of control information actually transmitted over the network, and thus maintaining a current state for the network;
determining if unexpected control information sequences have occurred, by comparing the detected control information sequences with the stored expected sequence of control information; and
determining if a particular station is malfunctioning, by examining the unexpected control information sequences.
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Accused Products
Abstract
The invention is a network monitor that passively detects sequences of control frame transmissions. Detected control frame sequences are compared to a model of the expected exchange of control frames. The monitor concludes that a malfunction has occurred when the detected control frame sequences do not match the frame sequences indicated by model. The monitor is quite useful with a network that uses a token passing protocol, since it can determine whether a particular station is working improperly by tracking whether the token is passed in the order proscribed by the expected token-passing sequence in the model. The monitor can detect and diagnose many types of network malfunctions. The monitor also observes and maintains statistics on network data traffic and configuration information, in real time. Since the monitor independently tracks which station has the token, statistics are developed on how much traffic is passing to and from bridges.
84 Citations
20 Claims
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1. A method for passively monitoring an operating data communications network, the network including a plurality of stations, the stations communicating by exchanging data and control information in accordance with a protocol, the method for monitoring comprising the steps of:
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storing information which represents an expected sequence of control information exchanged between two stations in the network; passively detecting sequences of control information actually transmitted over the network, and thus maintaining a current state for the network; determining if unexpected control information sequences have occurred, by comparing the detected control information sequences with the stored expected sequence of control information; and determining if a particular station is malfunctioning, by examining the unexpected control information sequences.
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2. A method for passively monitoring an operating data communications network, the network including a plurality of stations, the stations communicating by exchanging data and control information in accordance with a protocol, the control information including control frames having source and destination address fields, at least one type of control frame including at token-passing control frame used to control which station has the right to transmit at a particular time, the method comprising the steps of:
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storing information which represents an expected exchange of control frames between any two stations in the network; passively detecting sequences of control frames actually transmitted over the network; comparing the detected control frame sequences with the stored expected exchange of control frames, to determine if unexpected control frame sequences have been transmitted; and maintaining a token-holder record which indicates the identity of a present token-holder, the token-holder record updated only after the comparing step determines that an unexpected token-passing control frame sequence has not occurred. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A monitor for passively observing the operation of a data communications network, the network including a plurality of stations, the stations communicating by exchanging data and control frames in accordance with a protocol, the monitor comprising:
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receive modem means for receiving symbols representing signal levels being transmitted on the network; frame processor means, for interpreting series of symbols, for determining if a series of symbols represents a data frame, a control frame, or an invalid frame in accordance with the protocol, and for outputting actually received frames; and a protocol analyzer, including; memory means for storing information that represents an expected sequence of control frames between any two stations in the network; means for determining if an unexpected sequence of control frames has been received, by comparing the actually received frames with the stored expected sequence of control frames; and means for outputting an indication of unexpected control frame sequences as events. - View Dependent Claims (19, 20)
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Specification