Multiplex communications – Pathfinding or routing – Through a circuit switch
Reexamination Certificate
2000-05-24
2001-06-26
Chin, Wellington (Department: 2664)
Multiplex communications
Pathfinding or routing
Through a circuit switch
C370S368000, C370S391000, C370S412000
Reexamination Certificate
active
06252872
ABSTRACT:
TECHNICAL FIELD
The present invention generally relates to communication devices and, more particularly, to a port level data packet filter used to identify particular data packets.
BACKGROUND ART
There is an ever present demand for the efficient delivery of data packets between and among networked devices. Devices transmitting data packets include, but are not limited to, computers, telephones, local area networks, and wide area networks. The content of the data packets includes, but is not limited to, data signals, voice signals and video signals. Data packet delivery devices, including data packet switches (such as bridges and routers), modems and the like, are used to improve and facilitate the flow of data packets among the devices generating or transmitting the data packets.
Generally, each data packet has a series of frames. Each frame, or group of frames, specifies a certain characteristic of the data packet, such as communication protocol information, destination address, message content, etc. Each frame is also usually a specified number of bits long.
During data packet transmission, certain types of data packets can be selectively identified and specially handled based on attributes found in various frames of each data packet. Such identification of specific types of data packets is generally known as filtering. However, known filtering algorithms require processor intensive computations which may delay the transmission of the data packets and slow the flow of data within the network. Carrying out knowing filtering algorithms can also require a considerable amount of hardware.
SUMMARY OF THE INVENTION
According to one aspect of the invention, the invention is a method of identifying a target data packet from a series of data packets being received or transmitted by a communications device, each data packet having a series of data values. The method includes the steps of establishing at least one condition for the target data packet, each of the at least one condition specifying a particular data value being located in a particular position of the target data packet; determining whether a present data value from a data packet is located in the particular position specified by the condition and generating a position match indicator; determining whether the present data value contains the particular data value specified by the condition and generating a data value match indicator; comparing the position match indicator and the data value match indicator and generating a condition match indicator; and generating a positive evaluation result indicative of the presence of the target data packet when the condition match indicator for each of the a least one condition indicates that each of the at least one condition has been satisfied by the data packet.
According to another aspect of the invention, the invention is a method of identifying a target data packet from a series of data packets being received or transmitted by a communications device, each data packet having a series of data values. The method includes the steps of establishing a condition for the target data packet, the condition having a particular data position value and an associated particular data value; storing the particular data position value in a first content addressable memory, the first content addressable memory receiving a value related to a data position of a data value and the first content addressable memory generating a position match indicator; storing the particular data value in a second content addressable memory, the second content addressable memory receiving the data value and the second content addressable memory generating the data value match indicator; and comparing the position match indicator and the data value match indicator to determine if the condition for the target data packet has been satisfied by the transmitted data value.
According to another aspect of the invention, the invention is a port filter for identifying at least one target data packet. The port filter includes a first content addressable memory having a plurality of entries, the first content addressable memory storing a position value in each of the plurality of entry addresses; and a second content addressable memory having a plurality of entries, the second content addressable memory storing an expected data value in each of the plurality of entry addresses, the entries of the first content addressable memory and the second content addressable memory being logically paired such that the values stored in each pair of entries correspond to a condition used to identify the at least one target data packet.
REFERENCES:
patent: 5745488 (1998-04-01), Thompson et al.
patent: 5841874 (1998-11-01), Kempke et al.
patent: 5842040 (1998-11-01), Hughes et al.
patent: 5920886 (1999-07-01), Feldmeier
patent: 5930359 (1999-07-01), Kempke et al.
patent: 6041058 (2000-03-01), Flanders et al.
Advanced Micro Devices , Inc.
Chin Wellington
Pham Brenda
Renner , Otto, Boisselle & Sklar, LLP
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