Digital Equipment Corporation

Cabletron Systems, Inc.

Enterasys Networks, Inc.

Alcatel Communications, Inc.

Jerry D Hutchison

Henry S Yang

Bruce A Schofield

Richard L Kirk

William R Hawe

William C Mallard, Jr

Bruce D Miller

Charles W Kaufman

Robert J Simcoe

G Paul Koning

Mark F Kempf

William Melaragni

Simon A Ginzburg

Jeffrey L Cooper

Cuneyt M Ozveren

Ernest Grella

A communication system includes plural nodes interconnected with an optical transmission medium capable of carrying plural bands of optical channels. A device at each node is coupled to the medium for dropping one or more bands, adding one or more bands, and passively transmitting other bands such that a pair of nodes can communicate directly using a band common to the respective bands. One band of the bands associated with each of a first set of nodes overlaps with one band of the bands associated with each of a second set of nodes. Multiple overlapping bands provide a high level of wavelength termination diversity. An optical management bus system and method connects plural hybrid optical/electrical cables between transmission equipment and optical modules which connect to network fibers to provide a set of electrical connections that can be used to determine optical interconnections in an optical shelf configuration. A particular optical module can be identified as the root of an optical branching tree at a node and thereby the unique termination point of a network fiber such that a physical fiber topology can be associated with the logical fiber topology.

Communication system and method with optical management bus

Communication system and method with optical banding

A method for improving modal bandwidth in computer networks using multimode optical fiber and laser sources is disclosed in which an annular beam is generate by the laser source, thus preventing center fiber transmission modes from reaching the detector. This prevents or lessens a pulse-splitting effect at the detector. The annular beam is generated preferably by configuring a vertical cavity surface emitting laser to have a center totally-reflecting block of 5-7 microns to generate a substantially dark-centered beam.

Method and system for preventing low order optical transmission modes in multimode optical fiber computer network using annulus laser

A method of improving modal bandwidth in computer networks using multimode optical fiber and single mode sources is disclosed in which the optical signal from a center of the optical fiber is prevented from reaching the detector. This is accomplished according to a number of different techniques including the use of opaque spots on the fiber media/fiber couplers or the use of dark-cored fiber couplers. These configurations prevent pulse splitting that occurs in single mode source/multimode fiber systems by preventing light from the multimode fiber's center from interfering with the detector. When this is achieved, the detector is insulated from the effects of pulse splitting, supporting increased data rates by increasing the modal bandwidth.

Method and system for removal of low order optical transmission modes to improve modal bandwidth in a multimode optical fiber computer network

A method for improving modal bandwidth in computer networks using multimode optical fiber and single mode sources is disclosed in which the optical signal from a center of the optical fiber is blocked from reaching detector. This is accomplished according to a number of different techniques including the use of opaque spots on the fiber media/fiber couplers or the use of dark-cored fiber couplers. These configurations prevent pulse splitting that occurs in single mode source/multimode fiber systems by preventing light from the multimode fiber's center from interfering with the detector. When this is achieved, the detector is insulated from the effects of any pulse splitting, supporting data rates of greater than one GBPS by increasing the modal bandwidth.

Method and system for removal of low order optical transmission modes in

The input bandwidth of a data transfer device is increased by altering the conventional memory arbitration method in which a data cell is stored and a data cell is forwarded during each data transfer cycle. The input data rate is monitored and when the input data rate exceeds the maximum average throughput of the memory, the outcome of the memory arbitration cycle is changed so that the memory arbitration cycle consists of two stores (memory write operations) instead of one store and one forward (memory read operation.) In effect, the input memory arbitration process steals cycles from the output memory arbitration process when the input load exceeds that of the maximum average memory throughput. In accordance with one embodiment, the input data rate is monitored by examining input port FIFO buffers for the presence of data cells waiting for storage. Based on the results of the FIFO monitoring and the outcome of the current port arbitration cycle, a decision is made on the following port arbitration cycle whether to change the normal memory arbitration pattern.

Method and apparatus for reducing data loss in data transfer devices

A method and apparatus for substantially reducing electromagnetic radiation from a backplane used to interconnect multiple communication modules. Data signals to be transmitted onto the backplane are first scrambled using a pseudorandom code sequence, to reduce energy peaks in the radiation spectrum and to spread energy over a wider bandwidth. Signals received from the backplane are descrambled using an identical pseudorandom code sequence. Data rate synchronization is provided by recovery of a data clock signal from the received scrambled signals, and data frame synchronization is provided by transmitting data frame headers as non-scrambled data. At a receiver module, the frame headers are detected and used to reset the descrambling operation.

High-speed backplane bus with low RF radiation

A switchable interface for conveniently coupling a network station of the CSMA/CD type to a network having any of a variety of communication media. The invention provides a single interface connector through which connection may be made directly to a twisted-pair medium, using the 10BASE-T protocol, or to a medium of a different type, through an AUI protocol and an appropriate media attachment unit. The interface connector has pin assignments chosen to minimize adverse effects of misconfiguring the station by connecting to a network having a protocol that is different from the one selected in the switchable interface. In one form of the invention, the switchable interface has the ability to determine the protocol being used by the network to which it is connected, and to switch the interface accordingly. Use of the common interface reduces station equipment cost and provides for increased user convenience, since only a single connector is needed to connect to a variety of media types.

Common interface for a network having different communication media

Method and apparatus for automatically switching an Ethernet station interface to choose between two protocols and, possibly, two external connector configurations, to adapt the station automatically to the correct one of two communication media types, such as the twisted-pair medium served by the 10BASE-T protocol, and other media types, served by the attachment unit interface (AUI). The invention continually tests for proper operation in the currently selected protocol, and switches to the other protocol upon failure of a test. If one of two available external connectors is used to connect the station to a network, the invention chooses between the connectors automatically, such that manual switching between them is not required.

Automatic selection of an interface for ethernet stations

A technique for synchronizing run-length-limited data transmitted over two parallel narrowband communication channels, such as in a token ring local area network using fiber distributed data interface (FDDI) protocols. A serial data stream to be transmitted is demultiplexed onto the two channels by sending sequential blocks of equal numbers of bits over alternate channels. In a receiver-multiplexer, block boundary synchronization is established during connection initialization by using a property of a required HALT code to detect block boundaries received in each channel. Skew compensation is effected by comparing the times of detection of the block boundaries in the two channels, and appropriately controlling a variable delay in at least one of the channels. The technique establishes reliable block boundary synchronization and skew error compensation during connection initialization, and if there is subsequent loss of synchronization, detected transmission errors will eventually result in connection reinitialization and reestablishment of synchronization.

Method and apparatus for transmission of communication signals over two

A duplicate address condition in a computer network may be detected by a station of the type for attachment to a computer communications network, the network capable of maintaining communications among a plurality of stations, the station having means for receiving a frame, the frame having a source address field and a frame control field; means for maintaining an individual address of the station; means for maintaining a source address list of address, the source address list not containing the individual address; means for determining that a contents of the source address field in the frame matches at least one address in the source address list; means for determining that the frame control field of the frame has a predetermined contents; and, means, responsive to the source address of the frame matching at least one address in the source address list and the frame control field of the frame having the predetermined value, for setting an indicator that a duplicate address condition exists. The predetermined contents of the frame control field further comprises an indication that the frame is a predetermined type of control frame. The predetermined type of claim may be a beacon frame, a claim frame, or some other MAC protocol frame. The list of alias addresses may be stored in a content addressable memory. A cyclical redundancy check may be used for determining that bits from the source address field and bits from the frame control field are error free.

Detection of duplicate alias addresses

RingOp/Claim oscillations due to duplicate addresses and transmit aborts are avoided by using token preserver frames to reset the TVX timer in a station. A communications network having a plurality of stations capable of transmitting frames onto the network, and the stations capable of detecting transmission on the network, and the stations capable of taking predetermined action in the absence of detecting the transmission for a predetermined first time interval, and a first timer for measuring the predetermined first time interval. Measuring a second predetermined time interval, the second predetermined time interval being chosen to be less than the first predetermined time interval; transmitting a reset frame onto the network by a selected station at time intervals substantially equal to the second predetermined time interval, and the reset frames being capable of causing a station to reset the first timer to a beginning value. The network may be a token controlled ring. The reset frame may be a token preserver frame.

Avoidance of false re-initialization of a computer network

An apparatus to detect stations having duplicated addresses, the stations of the type connected in a computer communications network, the stations of the type capable of having an assigned address and having a list of addresses for comparison with a destination address field of a frame detected on the network is disclosed. The apparatus does a transmit self test, and sets a self indicator to 'pass' in the event that the self test frame is received, and sets the self indicator to 'timeout' in the event that a timeout occurs. The apparatus does a neighbor response test, and sets a neighbor indicator to 'timeout' in the event that a timeout occurs, and sets the neighbor indicator to 'pass' in the event that a received response frame indicates no destination address match, and sets the neighbor indicator to 'fail' in the event that a received response frame indicates that a destination address match did occur. The apparatus tests both the self indicator and the neighbor indicator, and in response to the testing of the self indicator and the testing of the neighbor indicator sets a duplicate address indicator in one of three states, a first state of the three states indicating that there is no duplicate address detected, a second state of the three states indicating that there is a duplicate address, and the third state of the three states indicating an unknown condition.

Testing a communications network for duplicate station addresses

A method and apparatus for detecting invalid network topologies in a local area network (LAN). The stations comprising the LAN include single attachment stations (SAS), dual attachment stations (DAS), wire concentrators (WC), and DAS/WC combination stations. Adjacent stations exchange connection type information identifying a type of physical connection of the station sending the connection information. A station receiving the connection information determines whether the connection is valid for its physical connection type using a connection matrix. Invalid connections can result in a network topology where stations are physically connected, but are not logically connected, because the stations do not all form a primary ring. Invalid connections may be rejected and bypassed in each station. Alternately, a station detecting an invalid connection may reconfigure itself using an internal data switch. The actions of each station, taken together, achieve a globally designated primary ring.

Network topology control method and apparatus

An output controller in a repeater node for controlling data transfers in a data communication system in which each node is operated by an independent local clock. Nodes will occasionally delete idle bytes from a preamble to recenter an elasticity buffer. The output controller performs a process that requires the elasticity buffer to be progressively more full before deleting another idle byte from the preamble. Transmission of the start of a subsequent frame is delayed and additional idle bytes are transmitted when the number of idle bytes being transmitted is at or below a certain threshold. Multiple thresholds are utilized so that the amount of the delay can be adjusted.

Growing community of inventors

Littleton, MA, United States of America

Jerry D Hutchison