Network diagnostic apparatus and method

• US 4,750,175 A
• Filed: 08/29/1986
• Issued: 06/07/1988
• Est. Priority Date: 08/29/1986
• Status: Expired due to Term

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Pactel Communications Companies
• Inventors: Hodges, Robert D., Brenneman, William D.
• Primary Examiner(s): Smith, Jerry
• Assistant Examiner(s): BEAUSOLIEL JR, ROBERT W
• Application Number:
  US06/902,197
• Time in Patent Office: 648 Days
• Field of Search: 371/22, 371/15, 371/16, 375/10, 370/13, 370/14, 370/15, 370/17, 379/25, 379/26
• US Class Current: 370/216
• CPC Class Codes: G06F 11/08 Error detection or correction by redundancy in data representation, e.g. by using checking codes
• CPC Class Codes: G06F 11/22 Detection or location of defective computer hardware by testing during standby operation or during idle time, e.g. start-up testing
• CPC Class Codes: G06F 11/2273 Test methods
• CPC Class Codes: G06F 11/2294 by remote test
• CPC Class Codes: G06F 11/2736 using a dedicated service processor for test
• CPC Class Codes: G06F 11/277 with comparison between actual response and known fault-free response
• CPC Class Codes: H04L 43/50 Testing arrangements

Abstract

A system for testing a data processing network and diagnosing malfunctions therein is disclosed. It is assumed that the data processing network includes a plurality of processing units coupled by communication paths in which each processing unit communicates with one or more other processing units in the data processing network by sending and receiving data packets over one or more of the communication paths. The system includes probes and a local processor for creating modified data packets from the data packets present on the network communication paths. The modified data packets allow a central processing unit which is communication with the local processor to diagnose network errors while maintaining the security of the data contained in the original data packets.

Claims

1. A system for detecting and diagnosing malfunctions in a data processing network wherein a plurality of processing units are coupled by communication paths over which each processing unit communicates with one or more other processing units in said data processing network by sending and receiving data packets, each said data packet comprising a message component and a format component, said format component comprising information for detecting errors in transportation and information specifying the format of said data packet, and said message component comprising information to be delivered to a processing unit, said system comprising

means for detecting data packets at a predetermined point on one of said communication paths;

local processing means coupled to said detecting means for processing said detected data packets, said local processing means comprising;

means for separating each detected data packet into format and message components;

means for generating a modified data packet for each said detected data packet, said modified data packet comprising data specifying the format component of said detected data packet and a replacement message comprising information for determining if the message component of said detected data packet was erroneously transmitted, wherein the message component of said data packet can not be ascetained from said modified data packet; and

means for coupling said local processing means to a telephone line, said coupling means including means for transmitting a said modified data packet and information specifying the predetermined point at which said data packet was detected, over a telphone line in response to a signal received on said telephone line.

2. A system for detecting and diagnosing malfunctions in a data processing network wherein a plurality of processing units are coupled by communication paths over which each processing unit communicates with one or more other processing units in said data processing network by sending and receiving data packets, each said data packet comprising a message component and a format component, said format component comprising information for detecting errors in transmission and information specifying the format of said data packet, and said message component comprising information to be delivered to a processing unit, said system comprising

means for detecting data packets at a predetermined point on one of said communication paths;

local processing means coupled to said detecting means for processing said detected data packets, said local processing means comprising;

means for separating each detected data packet into format and message components;

means for generating a modified data packet for each said detected data packet, said modified data packet comprising data specifiying the format component of said detected data packet and a replacement message comprising information for determining if the message component of said detected data packet was erroneously transmitted;

means for coupling said local processing means to a telephone line, said coupling means including means for transmitting a said modified data packet and information specifying the predetermined point at which said data packet was detected, over a telephone line in response to a signal received on said telephone line; and

means coupled to said local processing means for coupling signals to a communication path in said data processing network at a predetermined point on said communication path, said coupling means being responsive to control signals received over said telephone line.

3. A system for dectecting and diagnosing malfunctions in a data processing network wherein a plurality of processing units are coupled by communiation paths over which each processing unit communications with one or more other processing units in said data processing network by sending and receiving data packets, each said data packet comprising a message component and a format component, said format component comprising information for detecting errors in transmission and information specifying the format of said data packet, and said message component comprising information to be delivered to a processing unit, said system comprising

means for detecting data packets at a predetermined point on one of said communciation paths;

local processing means coupled to said detecting means for processing said detected data packets, said local processing means comprising;

means for separating each detected data packet into format and message components;

means for generating a modified data packet for each said detected data packet, said modified data packet comprising data specifying the format component of said detected data packet and a replacement message comprising information for determining if the message component of said detected data packet was erroneously transmitted; and

means for coupling said local processing means to a telephone line, said coupling means including menas for transmitting a said modified data packet and information specifying the predetermined point at which said data packet was detected, over a telephone line in response to a signal received on said telephone line,

wherein said local processing means further comprises alarm means comprising means for detecting improper signal patterns on a specified one of said communication paths and means for generating signals on said telephone line in response to detecting a said improper signal pattern.

4. The system of claim 3 wherein said specified communication path comprises a plurality of conductors, each said conductor coupling digital signals between two processing units in said data processing network, and wherein said detecting means comprises:

means for detecting said digital signals at a predetermined point on each of N selected conductors chosen from said plurality of conductors;

means for assigning one of S states to each said conductor in response to the digital signals so detected wherein S is greater than 2;

means for generating a number having radix S, said number including a plurality of digits, one said digit corresponding to each one of said N selected conductor, each said digit being determined by the state of said conductor; and

means for comparing said generated number with a plurality of numbers and generating a signal if said generated number matches any of said plurality of numbers.

5. The system of claim 4 wherein S is equal to 4 and wherein said first state is assigned to a conductor having a steady potential below a first predetermined potential, said second state is assigned to a conductor having a steady potential above a second predetermined potential, said third state is assigned to a conductor having an oscillating potential, said oscillations occurring in a predetermined frequency range, and said fourth state is assigned to all other conductors.

6. In a data processing network in which a plurality of processing units are coupled to each other by communication paths, each said processing unit communicating with one or more of said other processing units by sending and receiving data packets comprising a message component and a format component, said format component comprising information for detecting errors in transmission and information specifying the format of said data packet, and said message component comprising information to be delivered to a processing unit, said data processing network including means for detecting data packets at least one predetermined location in one of said communication paths and means for coupling signals to said communication path at said predetermined location, said data processing network also including local processor means for receiving commands over a telephone circuit and executing said commands, said commands including commands for processing and storing detected data packets and commands for coupling signals to said predetermined location in said communication path, a method for detecting and diagnosing malfunctions comprising the steps of:

detecting data packets at said predetermined location in said communication path;

separating each detected data packet into format and message components;

generating a modified data packet for each said detected data packet, said modified data packet comprising data specifying the format component of said detected data packet, and a replacement message comprising information for determining if the message component of said detected data packet was erroneously transmitted, wherein the message component of said data packet may not be ascertained from said modified data packet; and

transmitting data over a telephone circuit, said data specifying a modified data packet and the predetermined point at which said detected data packet was detected, in response to one of of said received commands.

7. In a data processing network in which a plurality of processing units are coupled to each other by communication paths, each said processing unit communicating with one or more of said other processing units by sending and receiving data packets comprising a message component and a format component, said format component comprising information for detecting errors in transmission and information specifying the format of said data packet, and said message component comprising information to be delivered to a processing unit, said data processing network including means for detecting data packets at least one predetemrined location in one of said communication paths and means for coupling signals to said communication path at said predetermined location, said data processing network also including local processor means for receiving commands over a telephone circuit and executing said commands, said commands including commands for processing and storing detected data packets and commands for coupling signals to said predetermined location in said communication path, a method for detecting and diagnosing malfunctions comprising the steps of:

detecting data packets at said predetermined location in said communication path;

separating each detected data packet into format and message components;

generating a modified data packet for each said detected data packet, said modified data packet comprising data specifying the format component of said detected data packet, and a replacement message comprising information for determining if the message component of said detected data packet was erroneously transmitted;

transmitting data over a telephone circuit, said data specifying a modified data packet and the predetermined point at which said detected data packet was detected, in response to one of said received commands; and

coupling signals to said predetermined point in said communication path in rsponse to one of said received commands.

8. A method for detecting malfunctions in a communication path including a plurality of conductors, each said conductor coupling digital signals between two processing units in a data processing network, a method for detecting a malfunction in said communication path comprising the steps of:

detecting said digital signals at a predetermined point on N selected conductors, each said selected conductor being chosen from said plurality of conductors;

assigning one of S states to each said conductor in response to the digital signals so detected wherein S is greater than 2;

generating a number comprising a plurality of digits, one said digit corresponding to each said selected conductor, each said digit being determined by the state of said selected conductor; and

comparing said generated number with a plurality of numbers and generating a signal if said generated word matches any of said plurality of numbers.

9. A means for detecting a malfunction in a communication path comprising a plurality of conductors, each said conductor coupling digital signals between two processing units, said detecting means comprising:

means for detecting said digital signals at a predetermined point on each of N selected conductors chosen from said plurality of conductors;

means for assigning one of S states to each said conductor in response to the digital signals so detected wherein S is greater than 2;

means for generating a number having radix S, said number including a plurality of digits, one said digit corresponding to each one of said N selected conductor, each said digit being determined by the state of said conductor; and

means for comparing said generated number with a plurality of numbers and generating a signal if said generated number matches any of said plurality of numbers.

10. A system for detecting and diagnosing malfunctions in a data processing network comprising a plurality of processing units coupled by communication paths over which each processing unit communicates with one or more other processing units in said data processing network by sending and receiving data packets, each said data packet comprising a message component and a format component, said format component comprising information for detecting errors in transmission, including at least one check sum, and information specifying the format of said data packet, and said message component comprising information to be delivered to a processing unit, a system for detecting and diagnosing malfunctions in said data processing network comprising:

means for detecting data packets at a predetermined point on one of said communicaiton paths;

local processing means coupled to said detecting means for receiving the data packets detected by said detecting means, said local processing means comprising;

means for separating each detected data packet into said format and message components;

means for generating a modified data packet for each said detected data packet, said modified data packet comprising data specifying the format component of said detected data packet, and a replacement message having a check sum equal to that of the message component of said detected data packet, wherein said message component of said data packet may not be ascertained from said modified data packet; and

means for coupling said local processing means to a telephone line, said coupling means including means for transmitting a said modified data packet and information specifying the predetermined point at which said data packet was detected, over a telephone line in response to a signal received on said telephone line.

11. A system for detecting and disagnosing malfunctions in a data processing network comprising a plurality of processing units coupled by communication paths over which each processing unit communicates with one or more other processing units in said data processing network by sending and receiving data packets, each said data packet comprising a message component and a format component, said format component comprising information for detecting errors in transmission, including at least one check sum, and information specifying the format of said data packet, and said message component comprising information to be delivered to a processing unit, a system for detecting and diagnosing malfunctions in said data processing network comprising:

means for detecting data packets at a predetermined point on one of said communication paths;

local processing means coupled to said detecting means for receiving the data packets detected by said detecting means, said local processing means comprising;

means for separating each detected data packet into said format and message components;

means for generating a modified data packet for each said detected data packet, said modified data packet comprising data specifying the format component of said detected data packet, and a replacement message having a check sum equal to that of the message component of said detected data packet;

means for coupling said local processing means to a telephone line, said coupling means including means for transmitting a said modified data packet and information specifying the predetermined point at which said data packet was detected, over a telephone line in response to a signal received on said telephone line; and

means coupled to said local processing means for coupling signals to a communication path in said data processing network at a predetermined point on said communication path, said coupling means being responsive to control signals received over said telephone line.