Method and apparatus for reordering frames

• US 5,619,497 A
• Filed: 03/15/1996
• Issued: 04/08/1997
• Est. Priority Date: 12/22/1994
• Status: Expired due to Term

• Current Assignee: EMC Corporation (Dell Technologies Inc.)
• Original Assignee: EMC Corporation (Dell Technologies Inc.)
• Inventors: Gallagher, Brian, Sandorfi, Miklos A.
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): TON, DANG T
• Application Number:
  US08/616,776
• Time in Patent Office: 389 Days
• Field of Search: 370/60, 370/94.1, 370/54, 370/60.1, 370/94.2, 370/94.3, 370/85.1, 370/112, 370/85.6, 370/61, 370/110.1, 370/85.13, 370/105.1, 370/82, 370/85.7, 370/74 , 370/95.3, 370/95.1, 379/93, 379/94, 379/95, 340/825.5, 340/825.51, 340/825.52, 340/825.02, 395/825, 395/830, 395/250, 395/856, 395/860, 395/864, 395/871, 395/842, 395/850, 395/280, 395/427, 359/139
• US Class Current: 370/394
• CPC Class Codes: H04L 49/20 Support for services
• 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 49/357 Fibre channel switches

Abstract

A method and apparatus for coupling a plurality of channels of a communications network to a node. The node includes a plurality of ports, each adapted for connection to a corresponding channel and a system interface adapted for connection to a plurality of node clients in the form of host computers, peripheral devices, network interfaces, etc. The node includes a receiver and transmitter dedicated to each port and common circuitry for controlling and processing frames received and/or transmitted by the plurality of ports. A frame prioritization circuit forwards frames received by a selected port to a frame handler for processing and a frame routing circuit routes frames processed by the frame handler to at least one of the ports associated with at least one destination node. The node further includes a frame header buffer associated with each port for temporarily storing the header of each frame received by the respective port prior to forwarding of the header to the frame handler.

Claims

1. A communications network for transmitting frames between nodes connected to the network, said network comprising:

(a) at least one node comprising;

(i) a plurality of ports capable of receiving frames from another node connected to said network substantially simultaneously and transmitting frames to another node connected to said network;

(ii) a frame handler for processing said frames received by said plurality of ports;

(iii) a multiplexer for forwarding a first frame received by a selected one of said ports to said frame handler; and

(iv) a demultiplexer for routing a second frame from said frame handler to at least a selected one of said plurality of ports; and

(b) a plurality of node clients in communication with said least one node, wherein each one of said node clients is associated with a corresponding one of said plurality of ports.

2. The communications network recited in claim 1 wherein said frame handler comprises a memory and a system interface for permitting communication between said frame handler and said plurality of node clients via a system bus.

3. The communications network recited in claim 1 wherein said node further comprises a plurality of receiver and transmitter circuits, each one connected to a respective one of said plurality of ports.

4. The communications network recited in claim 1 wherein said multiplexer comprises a control circuit for selecting said first frame in accordance with a priority assigned to each of said plurality of ports, wherein a first one of said plurality of ports is assigned a highest priority and a second one of said plurality of ports is assigned a lowest priority.

5. The communications network recited in claim 1 wherein said multiplexer comprises a control circuit for selecting said first frame in accordance with a predetermined order of said plurality of ports.

6. The communications network recited in claim 1 wherein each of said frames received by said plurality of ports comprises a header and data and wherein said at least one node further comprises a plurality of frame header buffers, each one corresponding to a respective one of said plurality of ports, for storing the header of frames received by said respective ports.

7. The communications network recited in claim 6 wherein said multiplexer comprises a control circuit for selecting said first frame in accordance with the number of frame headers stored in each of said plurality of frame header buffers.

8. The communications network recited in claim 1 wherein said demultiplexer comprises a control circuit responsive to said second frame and a look-up table for determining a destination node specified in the header of said second frame and for routing said second frame to at least one of said plurality of ports associated with said destination node.

9. The communications network recited in claim 1 wherein each of said plurality of node clients is one of a host computer, a data storage device, and a network interface.

10. The communications network recited in claim 4 wherein said first one of said plurality of ports assigned the highest priority provides a credit to other nodes connected to said communications network indicating a number of frames that said first one of said plurality of ports is capable of receiving, wherein said indicated number of frames is greater than a number of frames that said respective frame header buffer is capable of storing.

11. A node for use in a communications network having a plurality of channels, said network permitting transmission of frames including a header between said node and another node connected to said network, said node comprising:

a plurality of ports, each one associated with a respective one of said plurality of channels of said communications network;

a plurality of frame header buffers, each one associated with a respective one of said plurality of ports, for storing the header of frames received by said respective port;

a multiplexer for selecting a first frame stored in a one of said plurality of frame header buffers to be processed;

a frame handler for processing said first frame; and

a demultiplexer for routing a second frame designated for transmission to at least a selected one of said plurality of ports for transmission to said other node connected to said network.

12. The node recited in claim 11 further comprising a plurality of frame transmit buffers, each one associated with a respective one of said plurality of ports, for temporarily storing said second frame prior to transmission by said respective port, wherein said demultiplexer routes said second frame to the respective frame transmit buffer associated with said selected port.

13. The node recited in claim 11 wherein said frame handler comprises a memory and a system interface for permitting communication between said frame handler and a plurality of node clients.

14. The node recited in claim 11 further comprising a plurality of receiver and transmitter circuits, each one associated with a respective one of said ports and being connected between said respective port and the respective frame header buffer.

15. The node recited in claim 11 wherein said multiplexer comprises a control circuit for selecting said first frame in accordance with a predetermined priority assigned to said plurality of ports.

16. The node recited in claim 11 wherein said multiplexer comprises a control circuit for selecting said first frame in accordance with a predetermined order of said plurality of ports.

17. The node recited in claim 11 wherein said multiplexer comprises a control circuit for selecting said first frame in accordance with the number of frame headers stored in each of said plurality of frame header buffers.

18. The node recited in claim 11 wherein said demultiplexer comprises a control circuit responsive to said second frame and a look-up table, for determining at least one of said plurality of ports associated with a destination node specified in said second frame and for routing said second frame to said at least one port.

19. A method for processing frames received by a node of a communications network, comprising the steps of:

receiving frames at a plurality of ports of said node, said ports being capable of receiving said frames substantially simultaneously with respect to one another;

selecting a first frame received by one of said plurality of ports for forwarding said first frame to a frame handler of said node for processing; and

routing a second frame designated for transmission to a destination node by said node to at least one of said plurality of ports associated with said destination node.

20. The method recited in claim 19 wherein said frame selecting step comprises the steps of:

assigning a priority to each of said plurality of ports based on a predetermined criteria; and

selecting said first frame in accordance with a descending order of port priority.

21. The method recited in claim 19 wherein said frame selecting step comprises the step of selecting said first frame in accordance with a predetermined order of said plurality of ports.

22. The method recited in claim 19 wherein said frame selecting step comprises the steps of:

determining the number of frames received at each of said plurality of ports; and

selecting said first frame in accordance with a descending order of the number of frames received by each of said plurality of ports.

23. The method recited in claim 19 wherein said frame routing step comprises the steps of:

determining a destination node identity specified by a header portion of said second frame;

accessing a look-up table to determine at least one of said plurality of ports associated with said destination node; and

routing said second frame to said at least one port.