Data-processing network having non-deterministic access, but having deterministic access time

• US 6,178,177 B1
• Filed: 03/03/1997
• Issued: 01/23/2001
• Est. Priority Date: 02/27/1997
• Status: Expired due to Fees

• Current Assignee: Alcatel SA (Nokia Corporation)
• Original Assignee: Alcatel SA (Nokia Corporation)
• Inventors: Vautey, Bernard
• Primary Examiner(s): Geckil, Mehmet B.
• Assistant Examiner(s): Vaughn, Jr., William C.
• Application Number:
  US08/811,246
• Time in Patent Office: 1,422 Days
• Field of Search: 709/225, 709/233, 709/234, 709/235, 709/218, 709/249, 370/431, 370/445, 370/446, 370/447, 370/448, 370/458, 370/459, 370/460, 370/461, 375/347
• US Class Current: 370/445
• CPC Class Codes: H04L 12/413 with random access, e.g. carrier-sense multiple-access with collision detection [CSMA-CD]
• CPC Class Codes: H04L 49/351 for local area network [LAN], e.g. Ethernet switches

Abstract

A network includes stations that communicate with one another via a common medium using a non-deterministic protocol. The risk of collision between the two frames transmitted simultaneously by two stations is reduced by providing each station with a detector to determine whether there is a risk of collision based on counter updates for recent transmissions performed by the station. Each station further includes a delay to limit a station'"'"'s means bit rate to a predetermined maximum value when there is a risk of collision of data sent by the stations on the network. The maximum bit rate is chosen such that the sum of the values for all of the stations is less than the mean bit rate that can be accommodated by the common medium.

Claims

1. A data-processing network having non-deterministic access but having a deterministic access time, the network including a plurality of stations communicating with one another by accessing a common medium using a non-deterministic protocol, wherein each respective one of said plurality of stations includes:

means for detecting whether there is a risk of collision between two or more of the plurality of stations trying to access the common medium; and

a means for limiting a mean bit rate of the station over the common medium to a predetermined maximum value at least during periods in which there is a risk of collision between a plurality of stations trying to access the common medium, said maximum value being chosen such that a sum of the maximum values chosen for all of the stations is less than a mean bit rate that can be accommodated by the common medium.

2. A network according to claim 1, wherein the means for limiting the mean bit rate of the respective station comprise time-delay means authorizing a station to access the common medium after expiration of a delay, said delay starting at an end of a most recent access by the station, and said delay having a duration which is proportional to a duration of said most recent access.

3. A network according to claim 1, wherein the means for detecting whether there is a risk of collision between the plurality of stations comprises, means for determining whether at least one collision has taken place since a beginning of the most recent transmission performed by the station over the common medium, and for concluding that there is a risk of collision if at least one collision has occurred since the end of the most recent transmission performed by said station.

4. A data processing network including a plurality of stations communicating with each other by accessing a common medium using a non-deterministic protocol, each one of said plurality of stations including:

a collision counter to detect a number of collisions on the common medium;

a time delay counter receiving a clock signal, said time delay counter including a decrementing circuit;

a register storing an authorization flag; and

a processor interconnecting the time delay counter, register, and collision counter, the processor receiving an output of the time delay counter and a count value of the collision counter to set a state of the authorization flag in the register,

wherein said processor determines authorization access of the station to the common medium based on the state of the authorization flag.

5. The data processing network according to claim 4, wherein said authorization flag is set to an allow access state for the station when the decrementing circuit of the time delay counter counts down to zero from a predetermined value, wherein the predetermined value corresponds to a delay time for transmission of data from the station and an additional.

6. The data processing network according to claim 4, wherein said authorization flag is set to an allow access state for the station when the decrementing circuit of the time delay counter counts down to zero from a predetermined value, wherein the predetermined value corresponds to a delay time for transmission of data from the station and an additional interval, wherein the additional interval is proportional to a duration of a most recent access time of the station to the common medium.

7. The data processing network according to claim 5, wherein the additional interval is proportional to a duration of a most recent access time of the station to the common medium.

8. The data processing network according to claim 7, wherein said processor further stores a previous count value of the collision counter and when the authorization flag is set to a no access state, said processor compares the previous count value with the number of collisions presently detected by the collision counter and if the previous count value is equal to the presently detected number of collisions, the station is allowed access to the common medium.