International Business Machines Corporation

Jeffrey Robert Warren

Edward Stanley Suffern

John Walter Linville

Brad Alan Makrucki

Eric Lebrun

Pascal Francois

Stephen R Valley

George Michel Abdelnour

Frederic Raimbault

Data bandwidth on a congested link of a Carrier Sense Multiple Access with Collision Detection (CSMA/CD) network, is controlled by a Pause MAC Frame which carries information identifying devices causing the problem on the link. The Recipient of the Pause MAC Frame can use the information to deactivate selected devices on the congested link. As a consequence, the data bandwidth is reduced without shutting down the link.

Flow control mechanism

Flow control is implemented at a given node in a network of LAN switches by having the node monitor the occupancy levels of buffers or queues. When a buffer is found to be occupied or filled beyond a predetermined threshold level, a pause command is generated for the source currently supplying traffic to the buffer. A pause time PT is calculated using an equation which takes into account: the transmission rate of the identified source, the transmission rate of the output link servicing the congested buffer and queue length that can be occupied without a congestion condition being declared. To reduce the chance that queue lengths will &ldquo;oscillate&rdquo; about their threshold point due to multiple sources resuming transmission at the same time, each calculated pause time is adjusted to a randomly selected value PT(ran) falling within a range of PT&plusmn;kPT where k may be on the order of fifty percent.

Method and system for monitoring and controlling data flow in a network congestion state by changing each calculated pause time by a random amount

A Local Area Network (LAN) Switch includes conventional switching functions and integrated Remote Monitoring (RMON) Universal Feature Card (UFC). The UFC allows simultaneously statistically monitoring the traffic on all ports, 100% monitoring of the traffic on one port, and monitoring the internal LAN Switch switching fabric to obtain RMON statistics about the operation of networks attached to the LAN Switch.

Integrated network interconnecting device and probe

A system of high availablity synchronous bandwidth allocation comprising an FDDI segment to which are connected a first device for allocating synchronous bandwidth over the FDDI segment to any requesting device, and at least a second device for requesting synchronous bandwidth over the FDDI segment. The first device and a third device also connected to said FDDI segment, are capable of a exchanging information regarding the allocation of synchronous bandwidth to at least the second device, the third device can take over for the first device as synchronous bandwidth allocator, if the first device fails.

System of high availability synchronous bandwidth allocation over FDDI

To solve the problem raised by the allocation of synchronous bandwidth on a FDDI segment when this allocation is done by a centralized Allocator in an interconnected LAN domain, a Third Party Requestor receives from Quality of Service Allocator all information that it needs to ask for bandwidth reservation on the FDDI segment. Following the Station Management standard, the Third Party Requestor is able to act on behalf of the FDDI station that will submit synchronous traffic and ask for bandwidth allocation to a Synchronous Bandwidth Allocator. According to the Synchronous Bandwidth Allocator decision, the Third Party Requestor will then answer to the Quality of Service Allocator which will grant or deny the allocation over the whole path.

System for network wide bandwidth allocation

An LAN management facility for monitoring and managing errors on the physical links connecting the stations of a LAN. The facility includes, in part, an Enhanced Link Error Monitor (LEM). The Enhanced LEM continuously determines a Link Error Rate (LER) estimate as a function of time based upon the errors seen on the physical links. The enhanced LEM applies a link specific characteristic function to the LER estimate in order to determine an Adjusted LER Estimate. The link specific characteristic function takes into account the particular characteristics of the link experiencing the errors and is used to alter the station's responsiveness to these errors. The Adjusted LER Estimate is compared to alarm and cutoff thresholds in order to determine the appropriate action to take with respect to the link. By altering the link specific characteristic function, the Enhanced LEM will either become more or less responsive to errors on the link, thereby tolerating more or less errors in a greater or lesser period of time. In a preferred embodiment of invention, each station on the LAN maintains a Management Information Base (MIB) which contains the link specific characteristic function. The attributes in the MIB, including the link specific characteristic function, can be altered remotely by a LAN manager through one of the LAN stations acting as a proxy agent.

Growing community of inventors

Apex, NC, United States of America

Jeffrey Robert Warren