International Business Machines Corporation

Joel Erwin Geyer

Joseph Kinman Lee

Kenneth T Wilson

Vernon Roberts Norman

Joseph Gerald McDonald

Jeffrey James Lynch

Bradley S Trubey

Max Robert Povse

John M Mullen

Kathleen Miriam Wilhelm

Peter Anthony LaBerge

Anthony B Walker

Myrna Faye Milliser

In pause time based flow control systems having station-level granularity, a station or switch may detect congestion or incipient congestion and send a flow control frame to an upstream station, commanding that upstream station to temporarily stop (pause) sending data for a period of time specified in the flow control frame. The traffic pause gives the downstream station time to empty its buffers of at least some of the excess traffic it has been receiving. Since each downstream station operates independently in generating flow control frames, it is possible for the same upstream station to receive multiple, overlapping pause commands. If an upstream station which is already paused receives subsequent flow control frames from the same downstream station that triggered the pause, the upstream station's pause timer is rewritten using the pause times in the successive flow control frames. If the upstream station receives flow control frames from different downstream stations, the upstream station updates the pause timer only if the pause time in the most recent flow control message is greater than the remaining part of the previously established pause time.

Queue management for networks employing pause time based flow control

The problem with sharing or multi-tasking a single microprocessor across multiple ports is that it requires an elaborate and costly effort to adapt, modify, and rewriting of existing microcode. Extensive effort has gone into the development and testing of existing microcode that supports Token Ring. The re-use of the microcode, mostly in an &ldquo;as is&rdquo; condition is required to increase effectiveness and reduce costs. The present invention resolves these problems. It further describes a method that easily encapsulates existing hardware and allows the use of existing microcode to be extended to a multi-tasking environment, at a substantially reduced cost and with greater efficiency. Another embodiment of this invention describes a system and method to reuse a single existing Token Ring macro with embedded processor and microcode for multiple ports on a chip.

Method for encapsulating hardware to allow multi-tasking of microcode

An adapter which attaches Data Terminal Equipment (DTE) to a LAN includes a latch whose state is changed by conditions, such as a free token or a frame, on the LAN. The Output of the latch is used to calculate the bandwidth utilization of the LAN.

Real-time ring bandwidth utilization calculator by sampling over a

An adapter which attaches Data Terminal Equipment (DTE) to a LAN includes a latch whose state is changed by conditions, such as a free token or a frame, on the LAN. The output of the latch is used to calculate the bandwidth utilization of the LAN.

Real-time ring bandwidth utilization calculator, calculating bandwidth

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 network topology generator identifies addresses and locations of multiple stations connected to a single access port of a communications network by determining a pair of identifiable network units between which the multiple stations are connected, sequentially deactivating access ports between the pairs of identifiable network units and issuing selected message frames to the stations whose location is unknown. The message frames returning from said stations are monitored to detect the state of the Address Recognized (AR) bit. If the bit is set, this indicates that the station is still on the network. Therefore, the deactivate/polling routine is repeated until the AR bit in a returned message is in an 'off' state, indicating that the station is not on the network and is connected to the last deactivated port.

Enhanced serial network topology generation algorithm

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 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.

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Cary, NC, United States of America

Joel Erwin Geyer