International Business Machines Corporation

Steven Howard Johnson

Kenneth James Barker

Joseph Kinman Lee

Samuel Steven Allison

Hayden C Cranford, Jr

Peter D Beal

Gregory Francis Paussa

Theodore Allen Gary

Joseph Ronald Efferson, Jr

Mark Edmund Scheuer

Gregg Kreielsheimer

James Steele Gaillard

An adaptive interface and method of operation facilitate connection of a work station in a Local Area Network (LAN) using Shielded Twisted Pair (STP) cabling to an Ethernet 10/100BASE TX installation using Unshielded Twisted Pair (UTP). The work station is coupled through the adaptive interface to the STP cabling system emulating a given number of meters of UTP cabling. The interface adapter comprises at one end a RJ 45 connector adapted for connection to the STP cabling and at the other end a MIC_S token ring connector coupled to an Ethernet adapter through the STP cabling system. The adaptive interface includes programmatically controlled filters interconnecting the RJ 45 and MIC_S connectors. The filter comprises a series of 1 . . . N switchable lumped passive element units which can be sequentially connected into the STP cabling to emulate the amplitude attenuation and phase shift of a preselected length of UTP 5 cabling, typically in the range of 20 meters. In operation, the Physical Layer (PHY) in the communication system enters a start up sequence for the various circuits and cabling in the layer. During the start up sequence, the adaptive interface is bypassed. After an appropriate delay to allow PHY convergence or a bit error rate measurement, the PHY transmit/receive signals are examined for bit errors by a test unit. If there are no bit errors, no filter element is inserted in the STP cabling by the adaptive interface and the work station is coupled to the Ethernet installation. If there are bit errors, a first filter element is switched into the STP cabling by the adaptive interface. The bit error signals are re-examined. If there are no errors, the workstation is connected to the Ethernet installation. If bit errors continue to exist, the next element(s) of the filter is inserted into the STP cabling until the &ldquo;Nth&rdquo; filter element is reached. If bit errors continue to exist on the STP cabling after inserting the Nth filter in the STP cabling, a re-try test sequence is initiated by the adaptive interface and the start up sequence is repeated. If re-try is not initiated, a transmit error is displayed and the workstation/Ethernet installation cannot proceed without modification. A diagnostics menu is displayed and a set-up process determines with human intervention what system changes are needed for the workstation/Ethernet connection.

Adaptive interface apparatus and method for data terminal elements in a communication network transmitting and receiving ethernet over a shielded twisted pair cabling system

A LAN of the ethernet type employs CSMA/CD protocol for channel access by a plurality of network nodes. Each node includes a data processing system having a device driver and an adapter and transmits data packets to the LAN in accordance with the IEEE 802.3 standard. The adapter coupled is at one side to the network in either a half or full-duplex mode. The other side of the adapter is bound to the device driver which is dynamically tuned for reduced latency and increased network throughput, regardless of the transmitting mode of the node and the capture effect of the ethernet. Each device driver operates in a transmit chaining mode when the network is in a lightly loaded half-duplex, or full-duplex mode. The driver includes means for monitoring data packet collisions on a channel of the network. A &ldquo;collision rate&rdquo; or the percentage of data packets which were transmitted on the channel with collisions in a pre-selected time interval is calculated by the device driver. A &ldquo;collision threshold&rdquo; is assigned or calculated by the device driver. Data packets transmitted by each device driver are chained to increase network throughput when the &ldquo;collision rate&rdquo; is below the &ldquo;collision threshold&rdquo;. Transmit chaining of data packets is disabled for the device driver when the &ldquo;collision threshold&rdquo; is exceeded on the channel.

Dynamic transmit tuning for ethernet device drivers

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.

System and method for avoiding host transmit underruns in a

In a local area network, a system and a method to detect transmit underruns and retransmit frames between a sending station and a receiving station using a Media Access Control (MAC) device in lieu of a sending processor. The MAC device includes a MAC processor for transmitting data in blocks from a host buffer to a storage device, e.g., RAM for retransmission to the network via a Media Independent Interface (MII) unit. The MAC device includes a transmit logic unit which uses a control word set by the MAC processor to transmit data by frames from the storage device to the network. The transmit logic unit includes pointer control logic to identify the start address of the data and to track the data as read from the storage device to the network. When a transmit underrun occurs, the transmit logic recognizes the condition and resets the pointer logic to the start of the first frame for retransmission to the receiving station. During retransmission, the MAC processor continues to transfer data from the sending system to the storage device which eventually provides sufficient data to overcome the underrun condition. A frame is repeated if a underrun condition continues until the frame is transmitted without an underrun condition which eliminates the retransmission request of the receiving station to the sending station. The MAC device enables underruns to be transparent to the sending and receiving station.

System and method for automatic retry of transmit, independent of a host

An alterable device driver development system for supporting various operating systems, network protocols, and adapter hardware interfaces. Each device driver comprises a System, Network and Adapter software component, each component providing services to the other through its associated programming interfaces and being alterable or replaceable according to the requirements of an associated adapter hardware product. The System component supports a set of services defined by the device driver and which can be used by the Network and Adapter components. The Network component manages all interactions of the Adapter component with a network operating system or protocol stack and ensures its applicability and correctness in the context of the device driver operation. The Adapter component provides the functions for operating and managing all interactions with the adapter hardware. A Transformation Path in the Adapter component improves device driver performance by mapping network packet descriptors against adapter packet descriptors in data transferring processes.

Design methodology for device drivers supporting various operating

A LAN of the ethernet type employs CSMA/CD protocol for channel access by a plurality of network nodes. Each node includes a data processing system having a device driver and an adapter and transmits data packets to the LAN in accordance with the IEEE 802.3 standard. The adapter coupled is at one side to the network in either a half or full-duplex mode. The other side of the adapter is bound to the device driver which is dynamically tuned for reduced latency and increased network throughput, regardless of the transmitting mode of the node and the capture effect of the ethernet. Each device driver operates in a transmit chaining mode when the network is in a lightly loaded half-duplex, or full-duplex mode. The driver includes device for monitoring data packet collisions on a channel of the network. A 'collision rate' or the percentage of data packets which were transmitted on the channel with collisions in a pre-selected time interval is calculated by the device driver. A 'collision threshold' is assigned or calculated by the device driver. Data packets transmitted by each device driver are chained to increase network throughput when the 'collision rate' is below the 'collision threshold'. Transmit chaining of data packets is disabled for the device driver when the 'collision threshold' is exceeded on the channel.

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Cary, NC, United States of America

Steven Howard Johnson