Abstract: 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.

Abstract: 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 “as is” 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.