Quality of Service (QoS) support is provided by means of a Tiered Contention Multiple Access (TCMA) distributed medium access protocol that schedules transmission of different types of traffic based on their service quality specifications. In one embodiment, a wireless station is supplied with data from a source having a lower QoS priority QoS(A), such as file transfer data. Another wireless station is supplied with data from a source having a higher QoS priority QoS(B), such as voice and video data. Each wireless station can determine the urgency class of its pending packets according to a scheduling algorithm. For example file transfer data is assigned lower urgency class and voice and video data is assigned higher urgency class. There are several urgency classes which indicate the desired ordering. Pending packets in a given urgency class are transmitted before transmitting packets of a lower urgency class by relying on class-differentiated urgency arbitration times (UATs), which are the idle time intervals required before the random backoff counter is decreased. In another embodiment packets are reclassified in real time with a scheduling algorithm that adjusts the class assigned to packets based on observed performance parameters and according to negotiated QoS-based requirements. Further, for packets assigned the same arbitration time, additional differentiation into more urgency classes is achieved in terms of the contention resolution mechanism employed, thus yielding hybrid packet prioritization methods. An Enhanced DCF Parameter Set is contained in a control packet sent by the AP to the associated stations, which contains class differentiated parameter values necessary to support the TCMA. These parameters can be changed based on different algorithms to support call admission and flow control functions and to meet the requirements of service level agreements.

Tiered contention multiple access (TCMA): a method for priority-based shared channel access

A banking, retail or other transaction network can comprise a number of terminals, for example an ATM, where each terminal comprises a plurality of peripheral devices such as a user interface, card reader, receipt printer and cash dispenser. The applications software for the peripheral devices can be held in a central server located externally of the terminal and linked to the terminal through a communications link. The link can extend to the individual peripheral devices so that they are direct clients of the server. Additionally the individual peripheral devices can be connected to each other over the link to enable them to communicate directly with each other on a peer-to-peer basis. Each peripheral can have an independent control application. In use, the independent control applications may communicate with each other so that a peripheral operates in response to a signal generated by another peripheral. A peripheral for use in such a terminal, and a network of such terminals are also described. A mainframe or server computer accessing a banking or other information database (e.g., a legacy host) can be connected to the central server through an information signal connection.

Transaction processing systems

A method and system reduce interference between overlapping first and second wireless LAN cells in a medium. Each cell includes a respective plurality of member stations and there is at least one overlapped station occupying both cells. An inter-cell contention-free period value is assigned to a first access point station in the first cell, associated with an accessing order in the medium for member stations in the first and second cells. The access point transmits a beacon packet containing the inter-cell contention-free period value, which is intercepted at the overlapped station. The overlapped station forwards the inter-cell contention-free period value to member stations in the second cell. A second access point in the second cell can then delay transmissions by member stations in the second cell until after the inter-cell contention-free period expires.

Hybrid coordination function (HCF) access through tiered contention and overlapped wireless cell mitigation

Using low PF values in conjunction with traffic-adapted contention windows leads to substantial decreases in delay and jitter. In general, adaptation to traffic reduces contention or delay: opening up the contention window in congestion and closing it on relief. Residual backoff adaptation provides for the reduction of the already decremented backoff values of stations that interrupted the backoff countdown process due to a transmission. It is good to adapt both the contention window and the residual backoff in order to avoid jitter. Otherwise, if the contention window is reduced but residual backoffs stay unchanged, new arrivals will enjoy shorter backoff delays than older ones, resulting in greater jitter. Adjusting both preserves the relative ordering of backoff counter values, which implies also some form of age ordering. Different adjustments can be applied to different priority traffic.

Random medium access methods with backoff adaptation to traffic

In one example, a synchronization server includes logic operable to engage in a first synchronization session with a client device, wherein client modifications and server modifications may be exchanged based, at least in part, on synchronization data stored locally. The synchronization server further includes logic operable to initiate a query of a remote database (e.g., having data associated with the synchronization data) to determine differences between the synchronization data stored locally and associated data stored remotely. The synchronization server is further operable to initiate an exchange of further server modifications based on the differences between the synchronization data stored locally and the associated data stored remotely. In one example, the server may engage in a second synchronization session with the client device to update the client device with differences to the synchronization data stored locally and the remote database.

Data synchronization and device handling

Method for managing a data transmit queue (312), for use with a host (222) and a network interface device (216). The host (222) writes data buffer descriptors (314) into a transmit descriptor queue (312), and the network interface device (216) writes events (332) to notify the host (222) when it has completed processing of a transmit data buffer (310). Each of the transmit completion event descriptors (318) notify the host (222) of completion of a plurality of the transmit data buffers (310).

Transmit completion event batching

A network switch configured for switching data packets across multiple ports and for supporting trunked data paths uses an address table to generate frame forwarding information. When a link in a trunked data path experiences a change in its operating status, the trunk data path is reconfigured to reflect the current operating conditions, without reprogramming the address table or powering down the switch.

Method and apparatus in a network switch for handling link failure and link recovery in a trunked data path

Roughly described, method for managing data transmission between a host subsystem and a network interface device, in which the host writes data buffer descriptors into a DMA descriptor queue, and the network interface device writes completion events to notify the host when it has completed processing of data buffers. Each of the completion event descriptors notify the host of completion of data transfer between the NIC and one or more of the data buffers, and can also embed a queue empty notification inside the completion event.

Including descriptor queue empty events in completion events

A network switch having switch ports for communication of data packets with respective computer network nodes according to CSMA/CD protocol that resets a retry counter for counting data packet transmission attempts within any one of the respective switch ports if backpressure is asserted by that port. A retry limit value for the retry counter is modified to ensure that the total number of retrys does not exceed a maximum total number of allowable retrys. The resetting of the retry counter within a port after assertion of backpressure affords the port a greater probability of transmitting earlier under the CSMA/CD protocol, thus more quickly relieving congestion which may occur in the network switch. The modification of the retry limit value ensures that the number of retrys for the port does not exceed industry standards.

Apparatus and method for modifying a limit of a retry counter in a network switch port in response to exerting backpressure

A method and apparatus are disclosed for reclaiming frame buffers used to store data frames received by a network switch. The apparatus includes a multicopy queue for queuing entries corresponding to received data frames which must be transmitted by multiple output ports of the network switch, a free buffer queue for queuing frame pointers that identify locations in an external memory where reclaimed frame buffers are located, and a multicopy circuit that retrieves entries from the multicopy queue and determines if all copies of a received data frame have been transmitted by the specified output ports. The multicopy circuit also reclaims one or more frame buffers, based on the size of the received data frame. The present invention allows efficient reclaiming of frame buffers regardless of whether the received data frame is stored in a single frame buffer or multiple frame buffers.

Method and apparatus for reclaiming buffers using a single buffer bit

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