International Business Machines Corporation

University of South Florida

Kenneth J Christensen

Francis Edward Noel, Jr

Thomas E Stammely

Michael Steven Siegel

Norman Clark Strole

Lee C Haas

Raymond L Zeisz, Jr

Rudolf Eugene Rehquate

Jack S Chorpenning

Jerry Dagher

Steven Eric Polge

Beymer Bevill, Jr

Allen Leonid Roginsky

Anthony D Walker

Jim Philip Ervin

Max Robert Povse

Kenneth T Wilson

Richard Colbert Matlack, Jr

Norman Eugene Cox

Mehrgan Mostowfi

Mark R Nusekabel

Ingo McLean

Frances E Noel

Heidi Strayer

In one embodiment, automatically selecting a local communication channel for downloading a block of data via a network includes downloading portions of the block of data using first and second communication channels, determining a bottleneck exists on one of the local communication channels or on a component upstream from the channels, in response to determining the bottleneck exists on one of the local communication channels, selecting the communication channel that has the lowest energy cost and a download speed that meets a minimum threshold, and in response to determining the bottleneck exists upstream from the local communication channels, selecting the local communication channel having the lowest energy cost.

Systems and methods for automatically selecting a communication channel

A multi-port LAN switch is provided that enables attached network devices to both communicate directly and to insert into a token-ring network through an attached concentrator. Each port of the multi-port LAN switch has a first transformer, a second transformer, and a switching system. The first transformer has a first winding connected to a first connection of the port. The second transformer has a first winding connected to a second connection of the port. The switching system switches to a port mode or an adapter mode as a function of a mode signal transmitted to the port In the adapter mode, the switching system connects a second winding of the first transformer to a transmitter circuit in the port, and its connects a second winding of the second transformer to a receiver circuit in the port. In the port mode, the switching system connects the second winding of the first transformer to the receiver circuit in the port, and it connects the second winding of the second transformer to the transmitter circuit in the port. Each port of the multi-port LAN switch further includes a DC voltage source that is switchably connected to the first connection of the port through a first switch. Each port further includes a second switch that connects the second connection of the port to a DC return-path in a first position, and connects the second connection to the first connection when in a second position.

Multi-port LAN switch for a token-ring network

The invention provides that each of the components (i.e., switches, LAN segments, and workstations) is treated as a node for placement in a tree structure topology, with one switch at the top of the tree. Each switch may have other switches or LAN segments connected to it, with each LAN segment having a plurality of workstations attached to it. The workstations are the leaf nodes of the tree and cannot have anything connected to them. The inventive method for determining optimal partitioning is to calculate the mean switch delay, the mean segment delay, and the standard deviation as a function of the total number of workstations in the network, and to sum the values together. Finally, the invention applies a Tabu Search to the potential tree-structured solutions to the problem in order to rapidly and accurately determine the optimal network configuration.

Method and system for providing partitioning of partially switched networks

A route switching layer is provided to end stations on a local area network (LAN) segment between the network layer protocol stack and the LAN adapter device driver. The route switching layer reads the network layer protocol header in a data frame queued for transmission. If the data frame is destined for a station on a different LAN segment, the route switching layer compares the network layer address with entries stored in a local address table. If a match occurs, the route switching layer inserts the corresponding data link layer address from the table in the data link header that is appended to the data frame. The data frame is then transmitted directly from source to destination end station by a hardware switch. If an address table match does not occur, the source station route switching layer sends a query to a route server device for the data link layer address corresponding to the network layer address of the destination end station. The route server sends a response to the source station route switching layer which then stores the destination address information in the local address table.

Method and system for distributing network routing functions to local area network stations

Described is a method and apparatus which calculates Cyclic Redundant Check (CRC) for an entity from partial CRCs associated with segments of the entity. The entity includes a data packet segmented into a plurality of Asynchronous Transfer Mode (ATM) cells. The Packet CRC is calculated from the algorithm (A.sub.1 C.sub.1 +A.sub.2 C.sub.2 . . . +A.sub.N C.sub.N)/P with A.sub.i, i=1, . . . , N, representing a partial CRC associated with a particular ATM cell, C.sub.i, i-1, . . . , N, representing a Fixed Remainder and P is the CRC generation polynomial. The C.sub.i values are calculated and stored in a table. The partial CRCs (i.e., A.sub.i 's) are calculated by hardware generator and forwarded to a processor which selects the corresponding value of C.sub.i from the table and generates the CRC for the frame.

Method of partitioning CRC calculation for a low-cost ATM adapter

Disclosed is a method of transmitting ATM cells from a sending unit to a receiving unit on an ATM link wherein each of the ATM cells includes a header portion and a data portion. In the sending unit, a header portion is identified which is common to a set of subsequent ATM cells. Then, the common header portion is transmitted from the sending unit to the receiving unit followed by all data portions of the set of subsequent ATM cells. In the receiving unit, the original set of subsequent ATM cells is generated by using the common header portion.

Method and system for transmitting ATM cells on an ATM link

A LAN switch includes port modules which receive frames from their respective LAN segments and forwards the frames simultaneously to all output ports and to a port look-up function which determines the output port to which the frames should be forwarded. If the port look-up function identifies the output port, frame transmission is halted at all ports except the identified port. By performing the forwarding function and port look-up function simultaneously, a zero latency switch is provided.

Lan switch with zero latency

A multi-port LAN switch is provided that enables attached network devices to both communicate directly and to insert into a token-ring network through an attached concentrator. Each port of the multi-port LAN switch has a first transformer, a second transformer, and a switching system. The first transformer has a first winding connected to a first connection of the port. The second transformer has a first winding connected to a second connection of the port. The switching system switches to a port mode or an adapter mode as a function of a mode signal transmitted to the port. In the adapter mode, the switching system connects a second winding of the first transformer to a transmitter circuit in the port, and its connects a second winding of the second transformer to a receiver circuit in the port. In the port mode, the switching system connects the second winding of the first transformer to the receiver circuit in the port, and it connects the second winding of the second transformer to the transmitter circuit in the port. Each port of the multi-port LAN switch further includes a DC voltage source that is switchably connected to the first connection of the port through a first switch. Each port further includes a second switch that connects the second connection of the port to a DC return-path in a first position, and connects the second connection to the first connection when in a second position.

Data capacity mismatches between a communication node, including end node work stations, and a communication link usually require large buffer storage to prevent the loss of transmitted data frames due to transmission of an incomplete frame. Transmitted data frame continuity is maintained in the present invention by using small FIFO buffers in the node to store small portions of a data frame as data is sent and received. In addition, the data frame is maintained by stretching the transmitted frame on the link when necessary to prevent loss of the frame and compress the stretched frame when it is received from the link. The stretching and compressing is accomplished by inserting and removing non-data symbols, or command code words, in the transmitted and received string of data words. Small FIFO buffers (much less than a data frame in data capacity) operate on the fly to transmit and receive data without requiring contiguous transmission of a complete frame. At the sending node, non-data symbols are inserted in the frame between data words to fill gaps between strings of data bytes. At the receiving node, the non-data symbols are stripped from the received data frame to separate non-data symbols from data bytes. The non-data symbols are encoded command code words used to communicate status between the transmitting node and the receiving node. Transmitted encoded commands convey to a receiving node the status information of the transmitting node. The commands include Ready and Busy to indicate to the node at the opposite end of the link the status of the receive FIFO buffer in the node sending the commands.

Preserving data frame continuity across full-duplex LAN interface with

A method of automatically determining an attached device type for a multi-port LAN switch, and configuring the port based on the attached device type is provided. The method comprises setting a LAN switch port to a port mode, and determining, during a first period of time, whether an attached device is attempting to insert at the LAN switch port. If the attached device is attempting to insert during this first period of time, the method continues by configuring the LAN switch port in the port mode. If the attached device is not attempting to insert during the first period of time, the method continue by setting the LAN switch port in an adapter mode, transmitting a test frame to the attached device, and then determining, during a second period of time, whether a response frame is received from the attached device. If a response frame is received during the second period of time, the method further includes configuring the LAN switch port in the adapter mode.

Method and system of automatically configuring a LAN switch portof a

This invention relates to 'clear pipe' communication networks meaning the nodes and links handle a variety of data frame types depending on their communication protocols such as Token Ring, Ethernet, FDDI or ATM. More particularly, this invention relates to node/link interface adapters at nodes which include switching nodes and end nodes. The adapters identify data frame type and adapt the node/link adapter operative elements to handle the various types of data frames as they travel through the network. The invention identifies the frame type at the source, flags the frame type to the nodes by use of unique SDEL (start delimiter) symbols or codes, uses the SDEL codes as received with the frame at each node to find the destination address in the frame and to adjust the transmission rate for the frame. The transmission rate is adjusted by inserting null non-data symbols in the frame to effectively slow the data rate to the data rate capacity of the protocol.

Adapting switch port and work station communication adapters to data

A station in a communications network determines the mode (full-duplex or half-duplex) in which it communicates with a concentrator port by establishing a Registration routine between the station and the concentrator port. The station and concentrator port exchange frames which disclose the capabilities of the concentrator port. If the concentrator port has duplex capabilities, the station enters as a duplex station. Otherwise, the station enters in a half-duplex (token ring) mode.

Apparatus and method for determining operational mode for a station

A data communications system including a network and a number of data communication stations attached to the network wherein each of the stations includes a processor, a memory, a bus, and a communications adaptor for operatively connecting the processor and memory to the network, the communications adaptor including a means for monitoring network activity on a real time basis and enabling or disabling data compression when network activity exceeds a predetermined threshold.

System for selectively compressing data transferred in network in

In a local area network switch, a first mode of operation is selected wherein frames are examined for errors as the frames are passed from a source port to a destination port. The LAN switch calculates an error rate as a function of a percentage of the frames passing through the local area network switch which have errors. In response to the error rate exceeding a high error rate threshold, the operating mode is switched to a second mode wherein the entire frame is buffered and examined for errors before the frame is passed from the source port to the destination port. Thereafter, the operating mode may be returned to the first mode if the error rate falls below a low error rate threshold. The local area network switch may also change operating modes as a function of a trend, which indicates a rate of increase or decrease of the error rate.

Method and system in a local area network switch for dynamically

A system for utilizing a transmission media such as a token ring having multiple, independent channels operating in parallel. The invention provides optimal use of multi-channel bandwidth to a plurality of interconnected workstations, file servers, and other devices. The workstations and devices attach to the token ring via dedicated lobe rings connected to concentrators on the token ring. Each concentrator contains the processors, memory, and logic necessary to coordinate the transmission and receipt of data over the token ring among the interconnected workstations and devices. The multi-channel token ring provides increased bandwidth and reliability to an existing token ring without requiring modifications to existing physical devices, interfaces, or protocols.

Growing community of inventors

Apex, NC, United States of America

Kenneth J Christensen