Data transmission system having a backup testing facility

• US 5,689,513 A
• Filed: 03/29/1996
• Issued: 11/18/1997
• Est. Priority Date: 08/06/1993
• Status: Expired due to Term

• Current Assignee: Conexant Systems Incorporated (Synaptics Incorporated)
• Original Assignee: Fujitsu Limited
• Inventors: Okita, Ryoji, Ogawa, Tohru, Kawada, Michiko
• Primary Examiner(s): Beausoliel, Jr., Robert W.
• Assistant Examiner(s): Palys, Joseph E.
• Application Number:
  US08/624,055
• Time in Patent Office: 599 Days
• Field of Search: 395/183.19, 371/20.1, 371/20.2, 371/20.3, 371/20.4, 371/20.5, 371/20.6, 371/68.1, 371/68.2, 370/248, 370/249, 370/241, 370/242, 370/245, 370/247, 340/827
• US Class Current: 714/712
• CPC Class Codes: H04Q 11/0457 Connection protocols

Abstract

A data transmission system having, in addition to a normal system operation mode, a test mode wherein a plurality of stations confirm each other through sending and receiving check data for security confirmation and wherein the actual line switching operation is not performed. In the test mode, when notifying test data for confirmation of another station, the call terminating station side notifies the accurate data, while the call originating station side activating the test mode notifies deliberately changed check data thereby enabling a test for confirmation of the continuance of connection with a backup line without suspending communication with the working line.

Claims

1. A data transmission system having a backup testing facility, the data transmission system comprising:

at least two transmission apparatuses, one is a home data transmission apparatus and the other is an opposing data transmission apparatus both connected by both a working line and a backup line which is switched from the working line when an actual fault occurs in the working line in a normal mode, so as to continue a data transmission through the backup line, wherein

said home data transmission apparatus is operative to start a backup line test in a test mode between the home data transmission apparatus and said opposing data transmission apparatus by transmitting a call to the opposing data transmission apparatus, via said backup line, and

said at least two data transmission apparatuses each comprise check data generating means, check data transmitting means and check data receiving means for generating, transmitting and receiving check data among each other so that the home data transmission apparatus confirms whether the backup line is normal or not without switching from the working line to the backup line idle in the test mode, the check data generating means is coupled to the check data transmitting means and the check data receiving means.

2. A data transmission system as set forth in claim 1, wherein, in the test mode,

when the opposing data transmission apparatus receives first downstream check data transmitted from said check data generating means of said home transmission apparatus, said opposing data transmission apparatus transmits second upstream check data, created by raid check data generating means of said opposing data transmission apparatus using the first down stream check data, to the home data transmission apparatus, and

when the home data transmission apparatus receives first upstream check data transmitted from said opposing data transmission apparatus, said home data transmission apparatus transmits second downstream check data, created by said check generating means of said home transmission apparatus using the first downstream check data, to the opposing data transmission apparatus.

3. A data transmission system as set forth in claim 2, wherein said home data transmission apparatus, which activates said test mode, produces said second downstream check data composed of deliberately modified data or artificially constructed fixed data to incorrectly respond to said opposing data transmission apparatus, so that the opposing data transmission apparatus initiates no switching from said working line to said backup line.

4. A data transmission system as set forth in claim 3, wherein said second downstream check data is data obtained by the check data generating means of the home transmission apparatus performing bit inversion on normal second downstream check data to be sent back to said opposing data transmission apparatus if said actual fault occurs.

5. A data transmission system as set forth in claim 3, wherein said second downstream check data is data obtained by said check data generating means randomizing normal second downstream check data to be sent back to said opposing data transmission apparatus if said actual fault occurs.

6. A data transmission system as set forth in claim 2, wherein said home data transmission apparatus activates said test mode if the home data transmission apparatus is instructed to carry out a backup line test from an external monitor.

7. A data transmission system having a backup testing facility, the data transmission system comprising:

at least two transmission apparatuses, one is a home data transmission apparatus and the other is an opposing data transmission apparatus both connected by both a working line and a backup ling which is switched from the working line when an actual fault occurs in the working line in a normal mode, so as to continue a data transmission through the backup line, wherein

said home data transmission apparatus is operative to start a backup line test in a test mode between the home data transmission apparatus and said opposing data transmission apparatus by transmitting a call to the opposing data transmission apparatus, via said backup line, and

said at least two data transmission apparatus transmit and receive check data among each other so that the home data transmission apparatus confirms whether the backup line is normal or not without switching from the working line to the backup line idle in the test mode,

wherein when the opposing data transmission apparatus receives first downstream check data transmitted from said home transmission apparatus, said opposing data transmission apparatus transmits second upstream check data, created by said opposing data transmission apparatus using the first down stream check data, to the home data transmission apparatus,

wherein when the home data transmission apparatus receives first upstream check data transmitted from said opposing data transmission apparatus, said home data transmission apparatus transmits second downstream check data, created by said home transmission apparatus using the first downstream check data, to the opposing data transmission apparatus,

wherein said opposing data transmission apparatus has a first timer to produce, as said first upstream check data, a first timer value and said home data transmission apparatus having a second timer to produce, as said first downstream check data, a second timer value,

wherein said opposing data transmission apparatus further including a first calculation means for performing a first calculation by predetermined functions using, as variables, both said second timer value sent from said home data transmission apparatus and said first timer value, and

wherein said home data transmission apparatus further including a second calculation means for performing the second calculation by functions identical to said predetermined functions using, as variables, both said first timer value sent from said opposing transmission apparatus and said second timer value, so that second upstream data is created by data which is the same as the resultant data of the first calculation by said first calculation means, while said second downstream check data is created by data which is different from the resultant data of the second calculation by said second calculation means.

8. A plurality of data transmission apparatuses, each having a backup testing facility having a backup testing unit, wherein:

said first data transmission apparatus is operative in a working mode, to switch a working line to a backup line if an actual fault occurs in the working line, wherein both the working line and the backup line are connected to a second data transmission apparatus,

said first data transmission apparatus is operative, in a test mode to activate a backup line test by said backup testing unit, by sending first downstream check data and receiving first upstream data between said first and second data transmission apparatuses, wherein said backup testing unit is operative to send back second downstream check data, when second upstream check data is sent from said second data transmission apparatus, which second downstream check data is created by incorrectly responding to said first upstream check data, so as not to perform a switching operation from the working line to the backup line.

9. A plurality of data transmission apparatuses as set forth in claim 8, wherein the backup testing unit comprises:

first means for receiving an instruction signal which instructs carrying out the backup line test from an external monitor,

second means for judging if the instruction signal received by the first means is an instruction signal instructing activation of said test mode.

10. A plurality of data transmission apparatuses as set forth in claim 9, wherein said backup testing unit further comprises

third means for sending first downstream check data to said second data transmission apparatus and receiving first upstream check data sent from said second data transmission apparatus,

fourth means for carrying out a calculation using both said first downstream check data to be sent to the second data transmission apparatus and said first upstream check data received from the second data transmission apparatus to obtain said second downstream check data,

fifth means for comparing a resultant value obtained by said calculation at said first data transmission apparatus with a resultant value which is obtained through identical calculation at said second data transmission apparatus and sent, as said second upstream check data, therefrom,

sixth means for detecting if the above compared results coincide with each other and, when detecting coincidence, determines that said backup line is normal.

11. A plurality of data transmission apparatuses as set forth in claim 10, wherein the backup testing unit further comprises:

seventh means for producing and sending to said second data transmission apparatus calculation results different from the calculation results obtained by applying said predetermined calculation on the said sent first upstream check data at the fourth means when said sixth means judges that the backup line for connection with the second data transmission apparatus is normal.

12. A plurality of data transmission apparatuses as set forth in claim 10, wherein each data transmission apparatus comprises:

a data generating means for applying further processing to a normal resultant value obtained by said calculation to generate said second downstream check data different from this normal resultant value, which second downstream check data is to be sent to said second data transmission apparatus when determining said backup line is normal.

13. A plurality of data transmission apparatuses as set forth in claim 8, wherein each data transmission apparatus comprises discriminating means for judging if an instruction signal has been given instructing execution of said test mode.

14. A plurality of data transmission apparatuses as set forth in claim 11, wherein each data transmission apparatus comprises:

a determining means for judging that said backup line is normal and a switching operation from the working line to the backup line should not be performed.

15. A first data transmission apparatus connected with both a working line and a backup line which is switched from the working line if a fault occurs therein to perform a backup data communication with a second data transmission apparatus, the first data transmission apparatus comprising:

transmission means for sending data to said second data transmission apparatus;

reception means for receiving data from said second data transmission apparatus;

switching means for switching from said working line to said backup line and vice versa;

generation means for generating check data used for confirming whether the backup line is normal or not;

test means for receiving check data sent from said second data transmission apparatus and confirming whether the backup line is normal in accordance the thus received check data; and

changing means for changing the check data to be sent to said second data transmission apparatus when a test for the backup line is to be achieved.

16. A first data transmission apparatus as set forth in claim 15, wherein the first data transmission apparatus further comprises forming means for forming further check data by a predetermined function using, as variables, the check data generated inside the first data transmission apparatus and received check data from said second data transmission apparatus, wherein second check data is sent to said second data transmission apparatus, the second check data being obtained by changing the said further check data by said forming means.

17. A first data transmission apparatus as set forth in claim 16, wherein said check data is generated based on a timer value, at an activation of said test for the backup line, given from timer means contained in each of the data transmission apparatus and the second data transmission apparatus.

18. A data transmission system including a home data transmission apparatus, an opposing data transmission apparatus and both a working line and a backup line connected between the above two data transmission apparatuses,

each of the data transmission apparatuses is comprised of:

transmission means for sending data to the data transmission apparatus of the other party,

reception means for receiving data from the data transmission apparatus of the other party;

switching means for switching from said working line to the backup line and vice versa; and

generation means generating check data used for confirming whether the backup line is normal or not,

said opposing data transmission apparatus further including a comparing means for comparing the check data generated in the opposing data transmission apparatus with the check data generating in and sent from said home data transmission apparatus and activating said switching means in the opposing data transmission apparatus if a coincidence between the above two sets of check data is detected by said comparing means, so that the working line is switched to the backup line.

19. A method for communicating data between a home data transmission apparatus and an opposing data transmission apparatus via a working line or a backup line if a fault occurs, comprising the steps of:

(i) sending first downstream check data generated in said home data transmission apparatus to said opposing data transmission apparatus;

(ii) sending back to said home transmission apparatus first upstream check data generated, responding to the received first downstream check data, in said opposing data transmission apparatus;

(iii) comparing said second upstream check data and said second downstream check data in each of said home data transmission apparatus and said opposing data transmission apparatus to confirm whether the backup line is normal or not; and

(iv) switching, if said second upstream check data and second downstream check data are found to coincide with each other at the above step for comparing, from the working line to the backup line.

20. A method as set forth in claim 19, wherein a step for confirming the match of the interface conditions between said home data transmission apparatus and said opposing data transmission apparatus is inserted before the step (i).

21. A method for communicating data between a home data transmission apparatus and an opposing data transmission apparatus via a working line or backup line if a fault occurs, comprising the steps of:

(i) communicating downstream check data and upstream check data between said two data transmission apparatus so as to conform that whether the backup line is normal or not; and

(ii) sending dummy check data, if the backup line is normal, from said home data transmission apparatus to said opposing data transmission apparatus, so that the opposing data transmission apparatus fails, due to said dummy data, to activate a switching from said working line to said backup line.

22. A method as set forth in claim 21, wherein a step for confirming the match of the interface conditions between said home data transmission apparatus and said opposing data transmission apparatus is inserted before the step (i).