System and method for avoiding host transmit underruns in a communication network
First Claim
1. In a local area network, a system for avoiding transmit underruns from a host system to a communications network using an adjustable threshold on a frame basis, wherein said threshold indicates the number of data blocks included in said frame comprising:
- a) a media access control (MAC) device coupled to the network;
b) a data bus interconnecting the host system and the MAC device;
c) means providing a block size of data to be transferred by frame from the host to the communication network via the data bus and the MAC device;
d) counter means including an up counter responsive to a first host timer tick and a down counter responsive to a second host timer tick for defining an up or down threshold in each frame; and
e) means for modifying the threshold in each frame to avoid transmit underruns.
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Accused Products
Abstract
A system and method to avoid transmit underruns from a host system to a communication network using an adjustable threshold on a frame basis. The host system includes a device driver, host descriptors and host buffer. The host descriptor define the number of blocks of data to be transferred from the host to the network via a Media Access Control (MAC) device. The MAC device includes a processor, a transmit storage device, and a medium independent interface coupled to the network. The MAC device is connected to the host system via a data bus. A host descriptor is generated for each frame of data transferred by the MAC device from the host to the network. The descriptor is generated by the device driver and provides the MAC processor with a block size of data to be transferred and a threshold in each frame indicating the number of blocks of data to be transferred from the host system to the MAC device to avoid an underrun before transmission to the communication network. The MAC processor generates and transmits a "retry" bit to the device driver when a transmit underrun occurs. The device driver modifies the threshold in subsequent frames to avoid transmit underruns by raising or lowering the thresholds according to the number of retries.
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Citations
14 Claims
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1. In a local area network, a system for avoiding transmit underruns from a host system to a communications network using an adjustable threshold on a frame basis, wherein said threshold indicates the number of data blocks included in said frame comprising:
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a) a media access control (MAC) device coupled to the network; b) a data bus interconnecting the host system and the MAC device; c) means providing a block size of data to be transferred by frame from the host to the communication network via the data bus and the MAC device; d) counter means including an up counter responsive to a first host timer tick and a down counter responsive to a second host timer tick for defining an up or down threshold in each frame; and e) means for modifying the threshold in each frame to avoid transmit underruns. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. In a local area network, a host system coupled to a communication network via a communication bus and a media access control (MAC) device, the host system including a device driver and timer;
- host descriptors; and
host buffer;
the MAC device including a processor; and
transmit storage device, a method for avoiding transmit underruns in host data transmitted to the communication network using an adjustable threshold on a frame basis, wherein said threshold indicates the number of data blocks include in said frame, comprising the steps of;a) establishing counters in the device driver; b) counting transmit time ticks from the timer; c) maintaining transmit up and down frame counters from the timer for frames transmitted during a "raise threshold" or "lower threshold" interval, respectively;
the time ticks for the "lower threshold" being longer than the time ticks for the "raise threshold"d) maintaining a transmit up and down frame retry counters from the timer for frames retried in the "raise threshold" and "lower threshold" intervals, respectively; and e) determining the optimum threshold for frame transmission without underruns based upon the counter status to raise or lower the transmit threshold in a frame to minimize the number of transmit underruns, the threshold being raised if a selected percentage of frames were retried during the "raise threshold" interval and being lowered if zero frames were retried during the "lower threshold" interval. - View Dependent Claims (11, 12, 13, 14)
- host descriptors; and
Specification