Method and apparatus for controlling latency and jitter in shared CSMA/CD (repeater) environment

• US 6,026,095 A
• Filed: 05/29/1997
• Issued: 02/15/2000
• Est. Priority Date: 09/27/1994
• Status: Expired due to Term

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: 3Com Corporation (HP Inc.)
• Inventors: Wang, Peter, Dalgic, Ismail, Tang, Wen-Tsung, Sherer, William Paul
• Primary Examiner(s): NGO, RICKY QUOC
• Application Number:
  US08/865,226
• Time in Patent Office: 992 Days
• Field of Search: 370/229, 370/230, 370/235, 370/242, 370/243, 370/245, 370/400, 370/401, 370/445, 370/447, 370/448, 370/462, 370/461, 395/280, 395/287, 395/289, 395/293, 395/297, 395/299
• US Class Current: 370/448
• CPC Class Codes: H04L 12/40013 Details regarding a bus controller
• CPC Class Codes: H04L 12/413 with random access, e.g. carrier-sense multiple-access with collision detection [CSMA-CD]
• CPC Class Codes: H04L 12/4625 Single bridge functionality, e.g. connection of two networks over a single bridge
• CPC Class Codes: H04L 47/2441 relying on flow classification, e.g. using integrated services [IntServ]
• CPC Class Codes: H04L 47/263 Rate modification at the source after receiving feedback
• CPC Class Codes: H04L 47/28 in relation to timing considerations
• CPC Class Codes: H04L 47/50 Queue scheduling
• CPC Class Codes: H04L 47/58 Changing or combining different scheduling modes, e.g. multimode scheduling
• CPC Class Codes: H04L 47/6225 Fixed service order, e.g. Round Robin
• CPC Class Codes: H04L 49/90 Buffering arrangements

Abstract

An improved computer network and network device uses characteristics of prior art shared network protocols to control the flow of data and access to the network among a group of transmitting nodes. The invention determines which nodes wish to send data when a collision occurs by detecting and recording which nodes participated in a collision. A scheduling routine is designed to give each connected node a chance to send. A transmission control mechanism is used to prevent a subset of transmitters from transmitting while allowing one ES to transmit without experiencing a collision. The invention has a number of applications including within an improved ethernet repeater in a multimedia ethernet.

Claims

1. In a shared network environment, a method for transferring data among nodes connected via said shared environment comprising the steps of:

allowing a plurality of nodes to attempt to transmit on the network;

when a collision occurs, detecting which nodes are colliding nodes;

selecting one of said colliding nodes to transmit and going silent on said one selected node while transmitting a signal to non-selected nodes to prevent further transmission from said non-selected nodes during an early part of an inter-packet gap so as to hold said non-selected nodes in a ready-to-transmit state whereby a non-selected node will transmit data immediately when it detects silence;

allowing said one selected node to transmit an amount of data;

when said one selected node is finished transmitting said amount of data, allowing all nodes to hear silence long enough so that said nodes detect an end of transmission and then transmitting a signal to prevent transmission to all but a second selected node, so that all but a second selected node remain in a deferral mode.

2. The method according to claim 1 further comprising the step of:

allowing a signal transmitted by a node that is not a selected node and was not a colliding node to cause a second collision on said shared network.

3. The method according to claim 1 further comprising:

continuing to select nodes to transmit in a round-robin fashion while holding non-selected nodes that have participated in a collision in deferral using a transmitted signal.

4. The method according to claim 3 wherein said nodes are always selected in the same round-robin order so as to minimize jitter.

5. The method according to claim 1 wherein said nodes are selected in part based on a priority indication in a data unit transmitted on said nodes.

6. The method according to claim 1 wherein said nodes are selected in part based on a priority indication associated with a node.

7. The method according to claim 1 wherein state is maintained so that a node that transmits is not allowed to transmit again until all other nodes that participated in a collision have an opportunity to transmit.

8. The method according to claim 1 wherein an amount of data that a selected node is allowed to transmit before another node is allowed to transmit consists of a single packet.

9. The method according to claim 1 wherein an amount of data that a selected node is allowed to transmit before another node is allowed to transmit consists of more than one packet.

10. The method according to claim 1 wherein an amount of data that a selected node is allowed to transmit before another node is determined by a time slot.

11. The method according to claim 1 wherein after a collision occurs a node is selected based on a first node to attempt a transmission.

12. A fixed computer readable medium containing computer program code that when loaded into an appropriately configured computer system and run will cause the computer to perform the method of claim 1.

13. A fixed computer readable medium containing computer interpretable instructions describing a circuit layout for an integrated circuit that, when constructed according to said descriptions and placed into an appropriately configured computer system, will cause the computer to perform the method of claim 1.

19. The method according to claim 1 wherein said transmitting a signal to non-selected nodes to prevent further transmission from said non-selected nodes comprises transmitting a signal that forces a collision on said non-selected nodes while allowing said selected node to transmit.

20. The method according to claim 1 further comprising:

storing a portion of said amount of data in a buffer before forwarding said data to said nodes; and

selecting an algorithm for selecting a next node to transmit based on characteristics derived from said stored portion.

21. The method according to claim 20 further comprising:

storing a portion of said amount of data in a buffer before forwarding said data to said nodes; and

selecting an algorithm for selecting a next node to transmit based on characteristics derived from said stored portion.

22. The method according to claim 1 wherein when a collision occurs, a first transmitting node is a selected node and is allowed to complete its transmission without experiencing a collision while a collision is transmitted to other nodes that attempt transmission.

14. A network intermediate system for connecting a plurality of nodes operating according to a shared CS/CD protocol comprising:

a plurality of ports for transmitting/receiving data with said nodes;

a collision table for remembering which ports experienced collision; and

a controller operatively connected to said ports and said table and capable of;

detecting a collision,

determining and storing information regarding which ports participated in the collision,

selecting a port for transmission, and

preventing transmission from ports not selected for transmission by transmitting a signal to said not selected nodes during an early part of an inter-packet gap so as to hold said not selected nodes in a ready-to-transmit state whereby a not selected node will transmit data immediately when it detects silence.

15. The device according to claim 14 wherein state is maintained so that a node that transmits is not allowed to transmit again until all other nodes have an opportunity to transmit.

16. The device according to claim 14 further comprising a data buffer for storing a unit of data received on a port prior to transmitting that packet out of all other ports.

17. The device according to claim 14 further comprising a preamble generating circuit, simultaneously routable to a plurality of ports, for holding said ports in deferral.

18. The device according to claim 14 further comprising a jamming circuit routable to one port, for jamming transmission on said port.