International Business Machines Corporation

3com Corporation

Kenneth T Wilson

Joseph Kinman Lee

Joel Erwin Geyer

Vernon Roberts Norman

Michael Steven Siegel

Norman Clark Strole

Kenneth J Christensen

Anthony D Walker

Thomas E Stammely

Bradley S Trubey

Wilson Earl Smith

Jay L Smith

John M Mullen

David E Bartolini

Jack S Chorpenning

Raymond L Zeisz, Jr

Robert W Downes

Richard H Waller

Kathleen Miriam Wilhelm

Edwin L Tucker

Ronald E Suciu

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

In a serial network which includes a hub having a plurality of ports each for attaching one or more stations a mechanism for correlating a list of stations developed in a poll cycle to the ports and for detecting and resolving ambiguities when the number of stations does not equal the number of active ports. The mechanism uses a combination of input and output buffers under control of the programmed hub processor for developing a list of stations connected to the hub. When the number of stations does not equal the number of active hub ports an upstream buffer is configured to transmit Duplicate Address MAC frames to a single port and the contents of a downstream buffer are used to resolve the ambiguity either on a single transmission or multiple single port transmissions.

Port address resolution device

Dual detection paths containing speed recognition devices automatically determine the rate at which data is being transmitted on a multi-rate digital data communications network such as a token ring network. The multiple detection paths operate simultaneously with each detection path provided with a Phase Lock Loop (PLL) and a pattern recognition device. The PLL and its associated pattern recognition device are made to operate at one of the known ring speeds. The ring speed is determined by the detection path which is able to recognize a predetermined data pattern from the network.

Token ring speed detector

A multi-frame stripping method for use in a token ring network utilizing early token release with multiple frames transmitted by multiple stations circulating around the ring. The method recovers the ring with minimum loss of data after detection of an error condition resulting in frame corruption. The transmitting station is responsible for removing its own frames from the ring. With one or more of its frames corrupted, a station terminates frame removal after the transmitter has finished transmitting when a frame is received from another station without code violation errors in the frame header if the frame counter has returned to its initial value. The station terminates stripping when only a single frame is transmitted and then becomes corrupted if an isolated ending delimiter is detected at the station. The station also terminates stripping in the multi-frame case when the ending delimiter of the last frame transmitted by the source station is received without code violation error in the I-bit, if each preceding ending delimiter is correctly detected regardless of data corruption occurring in any frame header. The method is applicable to the IEEE 802.5 and ANSI X3T9.5 (FDDI) standards.

Multi-frame stripping protocol for token ring networks

A method for correcting error weights in a communication system in which at least one error condition can result from more than one cause. Stations on the system send error reports to an error monitor station which maintains a count of the number of stations reporting an error having multiple causes and periodically corrects the error weights assigned to each station as a function of the maximum number of errors reported by any station only when the number of stations reporting a multiple cause error exceeds a predetermined value.

Apparatus and method for isolating and predicting errors in a local area

A method and apparatus for enabling the transmitter to decide the number of variable length frames that can be trasmitted within the token holding timer (THT) window. The last frame decision algorithm enables the transmitter to set the intermediate frame bit in the ending delimiter to the right state to indicate the status of each frame in the transmitted frame sequence. A look-ahead technique is used to check the remaining transmit time available in the THT time window, therefor, no ring bandwidth is wasted on partially transmitted aborated frames, effectively optimizing the throughput of the network. Since key variables in the last frame decision algoritm are softwar programmable, the algorithm is independent of ring speed. The algorithm counts transmitted octets instead of measuring transmission time in deciding whether to transmit an additional frame. The algorithm can be applied to either signal frame or multi-frame transmit mode and to either normal or early token release. It is applicable to both the IEEE 802.5 local area network standard for token ring networks and the AnSI X3T9.5 standard for FDDI.

Multi-frame transmission control for token ring networks

A frame stripping algorithm for use in a ring communication network utilizing early token release wherein multiple frames can exist on the ring at one time. The algorithm introduces two new strip terminating conditions which supplement two of the three conditions applicable to a normal token release scheme. The first of these conditions occurs when the source address in a received message is not the same as the receiving station's address and no code violation errors have been detected. The second condition occurs when the receiving station detects an isolated ending delimiter without a preceding starting delimiter.

Frame stripping protocol for early token release in a ring communication

A reconfigurable serial loop or ring communication system is provided with a method and apparatus which enables stations on the loop to ascertain the address of its nearest active upstream neighbor (NAUN). A Ring Poll Frame is generated and broadcast from an originating station. The Ring Poll Frame includes a Ring Poll command, a From Address and a reset Address Recognized (AR) control bit. The first active downstream station recognizes the command with the control bit in the reset state, copies the contents of the ring poll frame and sets the bit. The set bit inhibits subsequent downstream stations from copying the frame. The first active station then generates a substantially similar formatted ring poll frame and passes it downstream. The process is continued by downstream active stations until the originating station receives a ring poll frame having a reset control bit. The reset control bit is an indication that all stations on the loop know the address of its NAUN. A ring management station may use the ring poll process to acquire information relative to the location of active stations on the ring.

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Raleigh, NC, United States of America

Kenneth T Wilson