Method and apparatus for selectively discarding packets for blocked output queues in the network switch

• US 5,953,335 A
• Filed: 12/18/1997
• Issued: 09/14/1999
• Est. Priority Date: 02/14/1997
• Status: Expired due to Term

• Current Assignee: Advanced Micro Devices, Inc.
• Original Assignee: Advanced Micro Devices, Inc.
• Inventors: Egbert, Chandan, Kerstein, Denise, Erimli, Bahadir, Runaldue, Thomas J.
• Primary Examiner(s): Pham, Chi H.
• Assistant Examiner(s): NGO, RICKY QUOC
• Application Number:
  US08/992,428
• Time in Patent Office: 635 Days
• Field of Search: 370/230, 370/231, 370/235, 370/389, 370/390, 370/401, 370/412, 370/413, 370/414, 370/415, 370/416, 370/417, 370/418, 370/422, 370/463
• US Class Current: 370/390
• CPC Class Codes: H04L 12/18 for broadcast or conference , e.g. multicast
• CPC Class Codes: H04L 12/1868 Measures taken after transmission, e.g. acknowledgments
• CPC Class Codes: H04L 41/0213 Standardised network management protocols, e.g. simple network management protocol [SNMP]
• CPC Class Codes: H04L 49/103 using a shared central buffer; using a shared memory
• CPC Class Codes: H04L 49/20 Support for services
• CPC Class Codes: H04L 49/201 Multicast operation; Broadcast operation
• CPC Class Codes: H04L 49/255 Control mechanisms for ATM switching fabrics
• CPC Class Codes: H04L 49/30 Peripheral units, e.g. input or output ports
• CPC Class Codes: H04L 49/3009 Header conversion, routing tables or routing tags
• CPC Class Codes: H04L 49/3027 Output queuing
• CPC Class Codes: H04L 49/3054 Auto-negotiation, e.g. access control between switch gigabit interface connector [GBIC] and link
• CPC Class Codes: H04L 49/351 for local area network [LAN], e.g. Ethernet switches
• CPC Class Codes: H04L 49/354 for supporting virtual local area networks [VLAN]
• CPC Class Codes: H04L 49/45 Arrangements for providing or supporting expansion
• CPC Class Codes: H04Q 2213/1316 Service observation, testing
• CPC Class Codes: H04Q 2213/13162 Fault indication and localisation
• CPC Class Codes: H04Q 3/54591 Supervision, e.g. fault localisation, traffic measurements, avoiding errors, failure recovery, monitoring, statistical analysis

Abstract

An apparatus and method of controlling the transmission of copies of a frame of data from a multiport device, such as a multiport network switch, determines which ones of the ports are designated to transmit a copy of a multicopy frame received at the switch. The switch then determines which of these designated ports are not available to transmit a copy of the frame. The copies are transmitted from those designated ports that are available to transmit a copy of the multicopy frame, while the copies are discarded for those designated ports that are not available to transmit a copy of that multicopy frame.

Claims

1. A method of controlling transmission of copies of a frame of data through a plurality of ports, comprising the steps of:

designating the ports from which the copies of the frame are to be transmitted;

determining which of the designated ports are not available to transmit one of the copies of the frame; and

providing the copies of the frame to the designated ports that are available to transmit one of the copies of the frame and discarding the copies of the frame to be transmitted from the designated ports that are not available to transmit one of the copies of the frame.

2. The method of claim 1, wherein the step of designating the ports from which the copies of the frame are to be transmitted include generating a port vector based on destination address information in the frame, the port vector identifying the designated ports.

3. The method of claim 2, wherein each port has an associated output queue configured to queue a frame pointer that points to a location in memory in which the frame is stored, the method further comprising loading the frame pointers for the frames to be transmitted into the associated output queues of the ports from which the frames are to be transmitted.

4. The method of claim 3, further comprising each port retrieving the frame from the memory when the frame pointer for that frame exits the associated output queue for that port.

5. The method of claim 4, wherein the step of determining which of the designated ports are not available to transmit one of the copies of the frame includes checking the available capacity of the output queues, wherein a port is determined to not be available to transmit one of the copies of a frame when the associated output queue of that port has no available capacity.

6. The method of claim 5, wherein the step of discarding the copies of the frame to be transmitted includes the step of discarding the frame pointers to be loaded into the associated output queues of the designated ports that have no available capacity.

7. The method of claim 6, further comprising determining the number of frame pointers that were discarded for a frame.

8. A multiport network switch which transmits multiple copies of a single frame of data, the network switch comprising:

a plurality of ports from which frames of data are transmitted;

a port vector generator that generates a port vector which designates from which ports copies of a frame are to be transmitted;

a transmission arrangement configured to determine the availability of each port designated by the port vector to transmit a copy of the frame and transmit copies of the frames through the designated ports that are available to transmit a copy of the frame and to discard copies of the frames to be transmitted from the designated ports that are not available to transmit a copy of the frame.

9. The network switch of claim 8, wherein the transmission arrangement includes a plurality of output queues, with a respective one of the output queues being associated with a different one of the ports.

10. The network switch of claim 9, wherein the transmission arrangement includes a port vector FIFO configured to receive the port vector and determine the available capacity of each of the output queues associated with the designated ports.

11. The network switch of claim 10, wherein the port vector FIFO is further configured to load a frame pointer into the output queues associated with the designated ports for each copy of the frame to be transmitted if said output queues have the available capacity, the frame pointer pointing to a memory location at which the frame is stored, the output queues queuing the frame pointers, and wherein each port is configured to access the memory location pointed to by the frame pointer and transmit the frame stored at that memory location upon the frame pointer exiting the output queue associated with that port.

12. The network switch of claim 11, wherein the port vector FIFO is further configured to discard the frame pointers for each output queue associated with a designated port if the output queue does not have available capacity.

13. The network switch of claim 12, wherein the port vector FIFO is further configured to determine the number of frame pointers that are loaded into output queues for a particular frame, and the number of frame pointers that are discarded for that particular frame.