High speed bus structure in a multi-port bridge for a local area network

• US 6,442,168 B1
• Filed: 02/18/1998
• Issued: 08/27/2002
• Est. Priority Date: 09/17/1997
• Status: Expired due to Fees

• Current Assignee: Sony Corporation (Sony Group Corp.), Sony Electronics Inc. (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.), Sony Electronics Inc. (Sony Group Corp.)
• Inventors: Vasa, Suresh L.
• Primary Examiner(s): Nguyen, Chau
• Assistant Examiner(s): LEE, CHI HO A
• Application Number:
  US09/025,356
• Time in Patent Office: 1,651 Days
• Field of Search: 370/351, 370/401, 370/402, 370/412, 370/419, 370/463, 370/410, 370/414, 370/421, 370/423, 370/426, 370/428, 370/438, 370/439, 370/445, 370/450, 370/451, 370/454, 370/446
• US Class Current: 370/401
• CPC Class Codes: H04L 12/18 for broadcast or conference , e.g. multicast
• CPC Class Codes: H04L 12/42 Loop networks
• CPC Class Codes: H04L 12/462 LAN interconnection over a bridge based backbone
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/135 by jamming the transmission media
• CPC Class Codes: H04L 47/30 in combination with information about buffer occupancy at either end or at transit nodes
• CPC Class Codes: H04L 49/102 using shared medium, e.g. bus or ring
• CPC Class Codes: H04L 49/351 for local area network [LAN], e.g. Ethernet switches
• CPC Class Codes: H04L 49/90 Buffering arrangements
• CPC Class Codes: H04L 49/901 using storage descriptor, e.g. read or write pointers
• CPC Class Codes: H04L 49/9047 including multiple buffers, e.g. buffer pools
• CPC Class Codes: H04L 49/9073 Early interruption upon arrival of a fraction of a packet
• CPC Class Codes: H04L 49/9078 using an external memory or storage device
• CPC Class Codes: H04L 49/9084 Reactions to storage capacity overflow

Abstract

A high speed bus structure for a multi-port bridge for controlling the flow of data packets through the multi-port bridge by using a limited number of bus commands. The bridge includes a memory for storing packets and a plurality of ports. Each port includes a receive buffer, a transmit buffer and a memory pointer buffer. A data packet is received by the receive buffer of a port. As the packet is still being received, a look-up table is utilized to determine which is the appropriate destination port for the packet. The destination ports are notified of their status as destination ports by raising a signal line of the communication bus corresponding to each destination port, referred to as a “bit-map.” If the memory pointer buffer in the destination port is nearly full, the destination port generates a jam request. The source port receives the jam request and, in response, discards the incoming packet and sends a jam signal. If the destination port is available to receive the packet directly from the source port, the destination port receives the packet simultaneously as the packet is stored in the memory device. Once the packet is stored, a memory pointer is placed on the communication bus. The memory pointer is stored in the destination port until the packet can be retrieved from the memory for transmission by the destination port.

Claims

1. A multi-port bridge for connecting a plurality of segments of a local area network, the multi-port bridge comprising:

a. a plurality of ports, each port for interfacing between the multi-port bridge and one of the plurality of segments;

b. a communication bus having a plurality of signal lines, the bus coupled to each of the plurality of ports, wherein data packets are communicated between the ports via the bus and further wherein each packet is received into a receive buffer in the corresponding port and transferred to an assigned location in a memory common to each port; and

a control circuit coupled to the bus, wherein each one of the ports corresponds to one of the signal lines, and further wherein the control circuit applies a selected logic level to an appropriate one of the signal lines to condition a predetermined port to receive a data packet.

2. The multi-port bridge according to claim 1 wherein the control circuit notifies each port whether the port is a destination for the packet while the packet is still being received by the multi-port bridge.

3. The multi-port bridge according to claim 1 wherein a port that is not busy receiving or transmitting when the port is notified that it is a destination for the packet receives the packet while the packet is being transferred to an assigned location in the memory.

4. The multi-port bridge according to claim 3 wherein a port that is busy receiving or transmitting when the port is notified that it is a destination for the packet retrieves the packet from the memory after the port is no longer busy.

5. The multi-port bridge according to claim 4 wherein the packet has a plurality of destinations and at least one of the plurality of destinations at receives the packet while the packet is being transferred to the assigned location in the memory and at least one other of plurality of destinations retrieves the packet from the memory.

6. The multi-port bridge according to claim 1 wherein the memory is divided into portions, one portion for each port, and wherein the assigned location for each packet is within the portion of the memory assigned to the corresponding port.

7. The multi-port bridge according to claim 6 wherein each packet is stored in the portion of the memory assigned to the corresponding port is a circular fashion wherein more recently stored packets overwrite less recently stored packets.

8. The multi-port bridge according to claim 1 wherein each port that is a destination for a packet stores indicia of the assigned location in the memory for the packet.

9. The multi-port bridge according to claim 8 wherein the indica includes an identification number assigned to the packet and an address of the location in the memory assigned to the packet.

10. The multi-port bridge according to claim 9 wherein the identification number is stored in the memory in conjunction with the packet and when the packet is retrieved from the memory the identification number included in the indica is compared to the identification number stored in conjunction with the packet.

11. The multi-port bridge according to claim 9 wherein a port having stored indica of a location retrieves the packet stored at the location at an appropriate time after the packet is stored.

12. The multi-port bridge according to claim 1 wherein the packet has a maximum expected size and the receive buffer is smaller than the maximum expected size.

13. The multi-port bridge according to claim 8 wherein each port further comprises a transmit buffer for receiving packets to be transmitted by the port.

14. The multi-port bridge according to claim 13 wherein the packet has a maximum expected size and each transmit buffer is smaller than the maximum expected size.

15. A multi-port bridge for interconnecting a plurality of segments of a local area network, the multi-port bridge comprising:

a. a communication bus having a plurality of signal lines;

b. a plurality of ports coupled to the communication bus, each port for receiving data packets from a corresponding segment of the local area network and for transmitting data packets bridged by the multi-port bridge to the corresponding segment, wherein one signal line of the plurality is assigned to each port of the plurality and further wherein each packet is received into a receive buffer in the corresponding port and transferred to an assigned location in a memory common to each port; and

c. a control circuit coupled to the communication bus, wherein the control circuit determines which of the ports are a destination for each packet based upon a destination address contained in the packet wherein the control circuit notifies each port whether the port is a destination for the packet by applying a selected logic level to the signal line of each port, wherein the control circuit notifies each port whether the port is a destination for the packet while the packet is still being received by the multi-port bridge.

16. The multi-port bridge according to claim 15 wherein a port that is not busy receiving or transmitting when the port is notified that it is a destination for the packet receives the packet while the packet is being transferred to an assigned location in the memory.

17. The multi-port bridge according to claim 16 wherein a port that is busy receiving or transmitting when the port is notified that it is a destination for the packet retrieves the packet from the memory after the port is no longer busy.

18. The multi-port bridge according to claim 17 wherein the packet has a plurality of destinations and at least one of the plurality of destinations at receives the packet while the packet is being transferred to the assigned location in the memory and at least one other of plurality of destinations retrieves the packet from the memory.

19. The multi-port bridge according to claim 15 wherein the memory is divided into portions, one portion for each port, and wherein the assigned location for each packet is within the portion of the memory assigned to the corresponding port.

20. The multi-port bridge according to claim 19 wherein each packet is stored in the portion of the memory assigned to the corresponding port is a circular fashion wherein more recently stored packets overwrite less recently stored packets.

21. The multi-port bridge according to claim 15 wherein each port that is a destination for a packet stores indicia of the assigned location in the memory for the packet.

22. The multi-port bridge according to claim 21 wherein the indica includes an identification number assigned to the packet and an address of the location in the memory assigned to the packet.

23. The multi-port bridge according to claim 22 wherein the identification number is stored in the memory in conjunction with the packet and when the packet is retrieved from the memory the identification number included in the indica is compared to the identification number stored in conjunction with the packet.

24. The multi-port bridge according to claim 22 wherein a port having stored indica of a location retrieves the packet stored at the location at an appropriate time after the packet is stored.

25. The multi-port bridge according to claim 15 wherein the packet has a maximum expected size and the receive buffer is smaller than the maximum expected size.

26. The multi-port bridge according to claim 21 wherein each port further comprises a transmit buffer for receiving packets to be transmitted by the port.

27. The multi-port bridge according to claim 26 wherein the packet has a maximum expected size and each transmit buffer is smaller than the maximum expected size.

28. A method of controlling flow of packets in a multi-port bridge having a plurality of ports interconnected to a memory device by a communication bus, the multi-port bridge for interconnecting a plurality of segments of a local area network, the method comprising steps of:

a. receiving a destination address for a data packet in a source port;

b. determining which one or more of the plurality of ports are a destination port for the packet based upon the destination address;

c. notifying the one or more destination ports of their status as a destination port separate from a step of transmitting a data packet to the destination port;

d. assigning a location in the memory device to the packet;

e. forming indicia of the location;

f. receiving the indicia in the one or more destination ports; and

g. storing the packet at the location.

29. The method according to claim 28 wherein the source port obtains access to the communication bus a first time for initiating the steps of determining and notifying and wherein the source port releases the communication bus after completion of the steps of determining and notifying.

30. The method according to claim 29 wherein the source port obtains access to the communication bus a second time for initiating the step of storing and wherein the source port releases the communication bus after initiating the step of storing.

31. The method according to claim 30 wherein the source port obtains access to the communication bus a third time for completing the step of storing and wherein the source port releases the communication bus after completing the step of storing.

32. The method according to claim 28 wherein the step of determining comprises steps of:

a. transferring the destination address to a control circuit; and

b. comparing the destination address to entries in a table.

33. The method according to claim 28 wherein the step of notifying comprises steps of:

a. forming a bit-map for the packet wherein each of the plurality of ports is assigned a respective one signal line of the communication bus, the bit-map including a logic level for each signal line assigned to a port wherein the logic level is indicative of whether the respective port is a destination port for the packet; and

b. placing the bit-map on the communication bus.

34. The method according to claim 28 wherein the indica includes an identification assigned to the packet and an address in the memory device representative of the location.

35. The method according to claim 28 wherein the step of storing is performed while the packet is being received by the source port.

36. The method according to claim 28 further comprising a step of retrieving the packet from the location into at least one of the destination ports for the packet.

37. The method according to claim 36 wherein at least one of the destination ports for the packet obtains access to the communication bus a first time for initiating the step of retrieving and then releases the communication bus and obtains access to the communication bus a second time for completing the step of retrieving and then releases the communication bus.

38. The method according to claim 36 further comprising a step of transmitting the packet while the packet is being retrieved from the location.

39. The method according to claim 28 further comprising a step of receiving the packet from the source port into at least one of the destination ports for the packet while the packet is being stored at the location.

40. The method according to claim 39 further comprising a step of transmitting the packet while the packet is being received from the source port.

41. The method according to claim 39 further comprising a step of retrieving the packet from the location into at least one of the destination ports for the packet after the packet has been stored at the location.

42. A method of controlling flow of packets in a multi-port bridge having a plurality of ports interconnected to a memory device by a communication bus, the multi-port bridge for interconnecting a plurality of segments of a local area network, the method comprising steps of:

a. receiving a packet having a destination address from a segment associated with a source port for the packet into a receive buffer in the source port;

b. looking-up the destination address in a table for determining one or more destination ports for the packet;

c. assigning a location in the memory device to the packet;

d. forming a bit-map for the packet wherein each of the plurality of ports is assigned a respective one signal line of the communication bus, the bit-map including a logic level for each signal line assigned to a port wherein the logic level is indicative of whether the respective port is a destination port for the packet;

e. placing the bit-map on the communication bus;

f. loading the packet into the memory device at the location in the memory device assigned to the packet; and

g. determining whether each destination port is available to receive the packet and if any destination port is available to receive the packet, performing a step of receiving the packet into a transmit buffer in each available destination port from the source port simultaneously with loading the packet into the memory device.

43. The method according to claim 42 further comprising a step of transmitting the packet performed while the packet is being received into the transmit buffer of each available destination port.

44. The method according to claim 42 wherein the packet also has a data field and wherein the step of looking-up the destination address is performed while the data field is being received by the source port.

45. The method according to claim 42 wherein the step of loading the packet into the memory device is performed while the data field is being received by the source port.

46. The method according to claim 42 further comprising a step of storing indicia of the location in each destination port determined to be unavailable during the step of determining.

47. The method according to claim 42 further comprising a step of receiving the packet from the memory device into a destination port determined to be unavailable during the step of determining after the destination port becomes available.

48. The method according to claim 47 further comprising a step of transmitting the packet performed while the packet is being received from the memory device by the destination port determined to be unavailable during the step of determining.