Polling system that determines the status of network ports and that stores values indicative thereof

• US 5,862,338 A
• Filed: 12/30/1996
• Issued: 01/19/1999
• Est. Priority Date: 12/30/1996
• Status: Expired due to Term

• Current Assignee: Hewlett Packard Enterprise Development LP (Hewlett-Packard Enterprise Company)
• Original Assignee: Compaq Computer Corporation (HP Inc.)
• Inventors: Walker, William J., Kotzur, Gary B., Mayer, Dale J., Witkowski, Michael L., Hareski, Patricia E.
• Primary Examiner(s): Ramirez, Ellis B.
• Application Number:
  US08/774,602
• Time in Patent Office: 750 Days
• Field of Search: 370/392, 370/264, 370/282, 370/250, 379/92.03, 395/674, 395/200.33, 395/200.64, 395/200.63, 395/200.62, 395/200.47, 395/200.54, 340/825.08
• US Class Current: 709/224
• CPC Class Codes: H04L 49/254 Centralised controller, i.e. arbitration or scheduling
• 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]

Abstract

A multiport polling system for a network switch including a plurality of network ports, each including receive and transmit buffers. Each port includes port status logic for providing status signals indicative of whether a corresponding port has received data from a network device and whether a corresponding port has available space to receive data to transmit to a network device. The network switch further includes a switch manager for controlling data flow between the ports. The switch manager includes polling logic for periodically polling the port status logic of each port for receiving the status signals, and a memory for storing values indicative of the status signals for each port. In this manner, all of the ports are simultaneously polled in a singe query and the receive and transmit status of each port is maintained in the memory. This facilitates arbitration and control logic, which continuously reviews the memory to determine when to retrieve data from a source port and when to transmit data to one or more destination ports. The ports are preferably implemented with quad cascade devices for providing multiplexed status signals.

Claims

1. A network switch for enabling communication among a plurality of network devices, comprising:

a plurality of network ports that receive data from and transmit data to the network devices, each of said plurality of network ports including port status logic that provides status signals indicative of whether a corresponding network port has received data from a network device and whether a corresponding network port has available space to receive data to transmit to a network device; and

a switch manager coupled to said plurality of network ports that controls data flow between said plurality of network ports, said switch manager including;

polling logic that periodically polls said port status logic of each of said plurality of network ports and that receives said status signals from said plurality of ports in response to each poll; and

a memory that stores values indicative of said status signals for each of said plurality of network ports.

2. The network switch of claim 1, further comprising:

said polling logic including logic that periodically asserts a query signal and that receives a transmit status signal and a receive status signal from each of said plurality of network ports; and

said port status logic of each of said plurality of network ports including logic that receives said query signal and that asserts a transmit status signal indicative of whether a corresponding network port has room to receive data from said switch manager, and that asserts a receive status signal indicative of whether said corresponding network port has received data from a network device;

wherein said polling logic asserts said query signal and receives a plurality of transmit status signals and a plurality of receive status signals.

3. The network switch of claim 2, further comprising:

a plurality of multiport devices, each to implement a subset of said plurality of network ports and each including port status logic that receives said query signal and that provides a corresponding multiplexed transmit status signal and a corresponding multiplexed receive status signal indicative of the status of each of said subset of said plurality of network ports of each of said plurality of multiport devices; and

said polling logic receiving a plurality of multiplexed transmit status signals and a plurality of multiplexed receive status signals from said plurality of multiport devices to determine the status of each of said plurality of network ports.

4. The network switch of claim 3, wherein each of said plurality of multiport devices comprises a quad cascade multiport device for incorporating up to four of said plurality of network ports.

5. The network switch of claim 1, further comprising:

said memory including;

a transmit list indicative of which of said plurality of network ports have indicated having space to receive data to transmit to a network device; and

a receive list indicative of which of said plurality of network ports have indicated received data from a network device; and

said polling logic including;

a transmit state machine that monitors said status signals and that periodically updates said transmit list; and

a receive state machine that monitors said status signals and that periodically updates said receive list.

6. The network switch of claim 5, further comprising:

said transmit list including a transmit active bit for each of said plurality of network ports, wherein said transmit state machine sets a corresponding transmit active bit when a corresponding network port indicates having space to receive data to transmit to a network device, and wherein said corresponding transmit active bit is cleared when said corresponding network port is provided with data to transmit; and

said receive list including a receive active bit for each of said plurality of network ports, wherein said receive state machine sets a corresponding receive active bit when a corresponding network port indicates having received data from a network device, and wherein said corresponding receive active bit is cleared when data is read from said corresponding network port.

7. The network switch of claim 5, further comprising:

said transmit list including a transmit priority count for each of said plurality of network ports, wherein said transmit state machine updates a corresponding transmit priority count when a corresponding network port indicates having space to receive data to transmit to a network device; and

said receive list including a receive priority count for each of said plurality of network ports, wherein said receive state machine updates a corresponding receive priority count when a corresponding network port indicates having received data from a network device.

8. The network switch of claim 1, wherein each of said plurality of network ports includes:

a transmit buffer that stores data for transmission to a network device; and

a receive buffer that stores data received from a network device.

9. The network switch of claim 8, wherein said port status logic of each of said plurality of network ports further comprises:

transmit status logic that asserts a transmit status signal indicative of said transmit buffer having at least an amount of available space equal to a predetermined bus transfer field size; and

receive status logic that asserts a receive status signal indicative of said receive buffer having received at least an amount of data equal to said bus transfer field size from a network device.

10. A network system, comprising:

a plurality of network devices to send and receive data packets; and

a network switch coupled to said plurality of network devices that transfers data packets between said network devices, said network switch comprising;

a plurality of network ports, each for coupling to at least one of said plurality of network devices to receive and transmit data packets, each of said plurality of network ports including;

a receive buffer that stores data received from a network device;

a transmit buffer that stores data for transmission to at least one network device; and

port status logic that provides status signals indicative of whether said receive buffer has received data from a network device and whether said transmit buffer has enough room to receive data to transmit to a network device; and

a switch manager coupled to said plurality of network ports to control data flow between said plurality of network ports, said switch manager including;

a memory that stores values indicative of said status signals for each of said plurality of network ports; and

polling logic that periodically polls said port status logic of each of said plurality of network ports, that receives said status signals from the plurality of network ports in response to each poll and that updates said memory.

11. The network system of claim 10, further comprising:

said polling logic including logic that periodically asserts a query signal and that receives a receive status signal and a transmit status signal from each of said plurality of network ports; and

said port status logic of each of said plurality of network ports including status logic that receives said query signal and that asserts a receive status signal indicative of whether said corresponding network port has received data from a network device, and that asserts a transmit status signal indicative of whether a corresponding network port has room to receive data from said switch manager;

wherein said polling logic asserts said query signal and receives a plurality of receive status signals and a plurality of transmit status signals.

12. The network system of claim 11, wherein said status logic of each of said plurality of network ports further comprises:

receive status logic that asserts a receive status signal indicative of said receive buffer having received at least an amount of data equal to a predetermined bus transfer field size from a network device; and

transmit status logic that asserts a transmit status signal indicative of said transmit buffer having at least an amount of available space equal to said bus transfer field size.

13. The network system of claim 10, further comprising:

said memory including;

a receive list indicative of which of said plurality of network ports have indicated received data from a network device; and

a transmit list indicative of which of said plurality of network ports have indicated having room to receive data to transmit to a network device; and

said polling logic including;

a receive state machine that receives said status signals and that periodically updates said receive list; and

a transmit state machine that receives said status signals and that periodically updates said transmit list.

14. The network system of claim 13, further comprising:

said receive list including a receive active bit for each of said plurality of network ports, wherein said receive state machine sets a corresponding receive active bit when a corresponding network port indicates having received data from a network device, and wherein said corresponding receive active bit is cleared when data is read from said corresponding network port; and

said transmit list including a transmit active bit for each of said plurality of network ports, wherein said transmit state machine sets a corresponding transmit active bit when a corresponding network port indicates having room to receive data to transmit to a network device, and wherein said corresponding transmit active bit is cleared when said corresponding network port is provided with data to transmit.

15. The network system of claim 13, further comprising:

said receive list including a receive priority count for each of said plurality of network ports, wherein said receive state machine updates a corresponding receive priority count when a corresponding network port indicates having received data from a network device; and

said transmit list including a transmit priority count for each of said plurality of network ports, wherein said transmit state machine updates a corresponding transmit priority count when a corresponding network port indicates having room to receive data to transmit to a network device.

16. A polling system for a network switch that continuously determines the receive and transmit status of each of a plurality of ports of the network switch, each of the ports responding to a query signal by providing a corresponding receive status signal indicative of the receive status of that port and providing a corresponding transmit signal indicative of the transmit status of that port, the polling system comprising:

a memory, including;

a receive list indicative of which of the ports have indicated having received data from a network device; and

a transmit list indicative of which of the ports have indicated being able to receive data to transmit to a network device; and

polling logic for coupling to each of the ports that periodically asserts a query signal, said polling logic including;

a receive state machine that receives the receive status signal of each of the plurality of ports and that updates said receive list; and

a transmit state machine that receives the transmit status signal of each of the plurality of ports and that updates said transmit list.

17. The polling system of claim 16, further comprising:

said receive list including a receive active bit for each of the ports, wherein said receive state machine sets a corresponding receive active bit when a corresponding port indicates having received data from a network device, and wherein said corresponding receive active bit is cleared when data is read from the corresponding port; and

said transmit list including a transmit active bit for each of the ports, wherein said transmit state machine sets a corresponding transmit active bit when a corresponding port indicates being able to receive data to transmit to a network device, and wherein said corresponding transmit active bit is cleared when the corresponding port is provided with data to transmit.

18. The polling system of claim 16, further comprising:

said receive list including a receive priority count for each of the ports, wherein said receive state machine updates a corresponding receive priority count when a corresponding port indicates having received data from a network device; and

said transmit list including a transmit priority count for each of the ports, wherein said transmit state machine updates a corresponding transmit priority count when a corresponding port indicates being able to receive data to transmit to a network device.