Advanced Micro Devices Corporation

Nortel Networks Corporation

Redback Networks Inc.

Jim Mangin

Mohan V Kalkunte

Jayant Kadambi

Shashank C Merchant

Gopal S Krishna

Derek H Pitcher

Hsinlun Jair

A method and apparatus for accessing management information base data is described. A method in a network element comprises collecting a first set of management information base (MIB) data in a framer's memory, maintaining a second set of MIB data that is periodically updated with the first set of MIB data, wherein the second set of MIB data is maintained separately from the first set of MIB data; and, in response to a request for the MIB data, transmitting the second set of MIB data.

Method and apparatus for accessing management information base data

An adaptive weighted round robin scheduling apparatus and method schedules variable-length frame transmissions from a plurality of output queues having different transmission priorities by first allocating, for each queue, a number of bandwidth segments for a bandwidth cycle and a number of transmission opportunities for a round robin cycle, and then processing the queues consecutively in a round-robin fashion, beginning with a highest priority queue, until none of the queues has any bandwidth remaining. More specifically, during each iteration of a round robin cycle, a queue is permitted to transmit a frame if the queue has at least one remaining transmission opportunity, the queue has a frame ready for transmission, and the queue has at least one remaining bandwidth segment, and furthermore the number of transmission opportunities for the queue is decremented by at least one. Upon transmitting a frame, the number of bandwidth segments for the queue is decreased by the number of bandwidth segments in the frame. If a queue has no frame ready for transmission, then the queue may be either penalized, in which case the number of bandwidth segments for the queue is reduced, or forced to forfeit its bandwidth segments, in which case any remaining bandwidth segments are reallocated to other queues and the number of bandwidth segments and the number of transmission opportunities for the queue are set to zero.

Servicing output queues dynamically according to bandwidth allocation in a frame environment

A technique for establishing a shortcut Virtual Channel Connection (VCC) in a Multi-Protocol Over ATM (MPOA) system detects a packet flow, and then determines whether to establish the shortcut VCC based upon an expected MPOA server response time. Specifically, an expected MPOA server response time is determined based upon an MPOA server response time history. The expected MPOA server response time is then compared to a predetermined MPOA server response time threshold to determine whether the expected MPOA server response time is within the predetermined MPOA server response time threshold. The shortcut VCC is established if the expected MPOA server response time is within the predetermined MPOA server response time threshold. Upon establishing the shortcut VCC, the MPOA server response time history is updated to reflect an actual MPOA server response time incurred when establishing the shortcut VCC.

Establishing shortcuts in a Multiprotocol-over-ATM system

An adaptive weighted round robin scheduling apparatus and method schedules variable-length frame transmissions from a plurality of output queue having different transmission priorities by first allocating, for each queue, a number of bandwidth segments for a bandwidth cycle and a number of transmission opportunities for a round robin cycle, and then processing the queues consecutively in a round-robin fashion, beginning with a highest priority queue, until none of the queues has any bandwidth remaining. More specifically, during each iteration of a round robin cycle, a queue is permitted to transmit a frame if the queue has at least one remaining transmission opportunity, the queue has a frame ready for transmission, and the queue has at least one remaining bandwidth segment, and furthermore the number of transmission opportunities for the queue is decremented by at least one. Upon transmitting a frame, the number of bandwidth segments for the queue is decreased by the number of bandwidth segments in the frame. If a queue has no frame ready for transmission, then the queue may be either penalized, in which case the number of bandwidth segments for the queue is reduced, or forced to forfeit its bandwidth segments, in which case any remaining bandwidth segments are reallocated to other queues and the number of bandwidth segments and the number of transmission opportunities for the queue are set to zero.

Delay times are modified in full-duplex Ethernet network devices by calculating in each network station a delay interval based on a size of a transmitted data packet and a desired transmission rate. The network station waits the calculated delay time before transmitting another data packet, ensuring that the overall output transmission rate of the network station corresponds to the assigned desired transmission rate. The desired transmission rate is received as a media access control (MAC) control frame from a network management entity, such as a switched hub. Hence, each station operates at the desired transmission rate, minimizing the occurrence of congestion and eliminating the necessity of PAUSE frames.

Arrangement for regulating packet flow rate in shared-medium,

Flow control signals in half-duplex and full-duplex networks are initiated and maintained based on the detected number of data bytes stored in a receive buffer from payload data of received data packets. If the number of stored data bytes exceeds a predetermined threshold, the network interface initiates flow control. Alternatively, the decision to initiate flow control may be based upon the rate at which the receive buffer is emptied compared to the number of stored data bytes in the receive buffer, or the rate the data bytes are stored into the receive buffer. The duration of the flow control is calculated as a wait time interval selected in response to the number of stored data bytes. The wait time may be selectively set as an integer multiple of slot times, or as a time interval based on the number of stored data bytes relative to the removal rate. Hence, the precise control and the initiation of the flow control for a specific wait time prevents loss of transmitted data while maintaining network throughput.

Arrangement for initiating and maintaining flow control in

Delay times are modified in Ethernet network devices by adding a slot time to the minimum interpacket gap (IPG) interval between uninterrupted consecutive transmissions by a network station. If a network station transmits a data packet and has another data packet to send, modified delay time prevents the station from contending for access of the media, enabling other stations having data to transmit to attempt access on the media. If a collision occurs during the transmission of a second successive data packet, the network station uses a modified collision arbitration and automatically sets the collision delay interval to zero for the first access attempt. If another collision occurs during the access attempt, the collision interval is calculated according to the truncated binary exponential backoff algorithm.

Method and apparatus avoiding capture effect by adding a slot time to an

Collision delay intervals are modified in Ethernet network devices transmitting priority data requiring a guaranteed latency by multiplying an integer multiple number of slot times with a fractional coefficient. A network device having priority data for transmission uses the conventional Truncated Binary Exponential Backoff (TBEB) algorithm during the first access attempt to calculate a collision delay interval from a randomly selected integer multiple of slot times. If the network device encounters another collision, the next randomly selected integer multiple of slot times is multiplied by the fractional coefficient. Use of the fractional coefficient during collision mediation on a half-duplex Ethernet network provides a bounded access latency for real-time and multimedia applications by granting the network device a higher probability of successfully accessing the network media.

Method and apparatus for prioritizing traffic in half-duplex networks

Delay times are modified in Ethernet network devices by adding a randomized time interval generated in accordance with a propagation delay between two network stations. A server in a client-server arrangement is given priority access over clients by adding to the clients' InterPacket Gap (IPG) interval a random time delay between one and two times the cable delay between the server and the corresponding client. The server can access the network media after the IPG interval, whereas clients must wait the additional random time delay before accessing the media, thereby improving server throughput and overall network throughput. Collision mediation is improved by adding a randomly selected integer multiple of a propagation delay between two stations, where the integer multiplier is randomly selected from a predetermined range of integers. The randomly selected integer multiple of the propagation delay provides a second dimension of random selection to minimize subsequent collisions and minimize the occurrence of capture effects in losing stations.

Method and apparatus for adding a randomized propagation delay interval

Delay times are modified in Ethernet network devices by adding an integer multiple of a delay interval to the minimum interpacket gap (IPG) interval, and decrementing a deferral counter storing the integer in each network station in response to detected activity on the media. Each station independently determines the number of stations active on the network media by counting the number of successful packet receptions following a corresponding detected collision. Once the number of detected collisions equals the number of stations (N) minus one, each station independently establishes a unique integer value from the range of zero to the number of detected collisions, i.e., up to the number of stations (N) minus one, by resetting the deferral counter to (N-1) after a successful transmission, and by decrementing the deferral counter upon detection of a successful transmission without collision by another station. The unique integer value ensures that each station has a different delay interval in accessing the media after sensing deassertion of the receive carrier. Each network station also includes a deferral timer that counts the maximum delay interval of (N-1) delay intervals plus the minimum IPG value, and thus establishes a bounded access latency for a half-duplex shared network.

Determining the number of active nudes on an ethernet network by

Efficient communication in a network having a minimum data transmission time interval wherein a data packet is transmitted beginning at a start of the minimum data transmission time interval. An end of the minimum data transmission time interval is determined and then at least one next data packet is transmitted after the data packet if the end of the minimum data transmission time is after the end of the data packet.

Efficiency of a network having a minimum data transmission time

Delay times are modified in Ethernet network devices by adding an integer multiple of a delay interval to the minimum interpacket gap (IPG) interval, and decrementing the integer in each network station in response to detected activity on the media. Each station has a unique integer value from the range of zero to the number of stations (N) minus one. The unique integer value ensures that each station has a different delay interval in accessing the media after sensing deassertion of the receive carrier. The station having a zero integer value will have its integer counter reset to (N-1) after a station transmits a data packet on the network, and the stations having nonzero integer values decrement their respective integer counters. Each network station also includes a deferral timer that counts the maximum delay interval of (N-1) delay intervals plus the minimum IPG value, and thus establishes a bounded access latency for a half-duplex shared network.

Rotating priority arrangement in an ethernet network

A network includes a combination of carrier-sense stations and Universal Multiple Access (UMA) stations using a time slot multiple access protocol. The network is configured to include assigned time slots for the respective UMA stations and unassigned time slots reserved for the carrier-sense stations to access the shared network media. Each of the UMA stations is provided with a corresponding assigned time slot and the total number of time slots. Since the UMA stations access the media only during the assigned time slot, the carrier-sense stations can contend for access to the media after waiting a minimum interpacket gap (IPG) after sensing deassertion of the receive carrier on the media. The UMA stations may also be modified to attempt access of the media using Ethernet-compliant, carrier-sense multiple-access with collision detection (CSMA/CD) protocol when a current time slot corresponds to a mixed-use time slot.

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San Ramon, CA, United States of America

Jim Mangin