Digital Equipment Corporation

At+t Corp.

Cabletron Systems, Inc.

Digital Equipment Corp., Patent Law Group

K K Ramakrishnan

Rajendra K Jain

Henry S Yang

Barry A Spinney

Dah-Ming Chiu

Anna Charny

Anthony G Lauck

An apparatus controls the transmission rates of a plurality of end stations in a computer network, and the network has at least one intermediate node. The intermediate node has a plurality of virtual circuits passing therethrough, where the virtual circuits are established between the end stations. The end stations transmit data packets at a plurality of discrete transmission rates. The end stations transmit data packets containing a field having transmission rate information. The intermediate node reads the transmission rate information for the virtual circuits, by the intermediate node detecting the transmission rate information in the field of a data packet which it receives. The intermediate node counts the number of virtual circuits using each of the discrete transmission rates. The intermediate node maintains an indication that a selected virtual circuit has been counted, and for not counting the virtual circuit more than once during a switch time interval. The intermediate node calculates a rate allocation value for the plurality of virtual circuits, and writes the rate allocation value into the field of the data packet in order to signal to the end station, and any intervening intermediate node, the calculated rate allocation value. A bit is stored in the intermediate node for each virtual circuit, each bit is initialized to a first value at the beginning of a switch time interval, and the bit is assigned a second value when a data packet having transmission rate information is detected in the selected virtual circuit by the intermediate node.

Method and apparatus for allocating a transmission rate to source end

A computational method and apparatus allocates transmission rate to source end nodes, and both reduces the computational complexity, and reduces the state information which must be retained concerning each VC, without significantly degrading convergence properties for the network. Also, the computational method is useful with either interval based or proportional schemes of flow control. A plurality of virtual circuits is established between source end stations and destination end stations, the plurality of virtual circuits passing through an intermediate node. The source end stations transmit data packets at a plurality of discrete transmission rates. The intermediate node counts the number of virtual circuits using each of the discrete transmission rates. The intermediate node maintains an indication that a select virtual circuit has been counted in the step above, and does not count the virtual circuit more than once during a switch time interval. The intermediate node, responsive to counting the number of virtual circuits using each of the discrete transmission rates, calculates a rate allocation value for the plurality of virtual circuits, the calculation is done periodically during the switch time interval. The rate allocation value is written into the field of the data packet in order to signal to the source end station, and any intervening intermediate node, the rate allocation value calculated above.

Network flow control having intermediate node scalability to a large

Method and apparatus for operating a digital communication network to avoid congestion by detecting load conditions at intermediate stations exceeding an overload condition, and flagging information packets associated with those streams of traffic accounting for more than their fair share of throughput at such overloaded stations.

System for setting congestion avoidance flag at intermediate node to

Method and apparatus for operating a digital communication network to avoid congestion by detecting load conditions at intermediate stations exceeding an overload condition and adjusting the rates at which source stations that are utilizing more than their fair share of throughput capacity transmit information through the intermediate stations.

Avoiding congestion system for reducing traffic load on selected end

In accordance with principles of the invention, a frame removal mechanism for token ring networks is disclosed. The disclosed system uses strip delimiter frames. The system transmits one or more information frames onto a computer network. The system further transmits one or more strip delimiter frames onto the computer network after the information frame transmission. The system detects strip delimiter frames on the computer network, and strips information frames received from the computer network after the information frame transmission is begun and until one of the strip delimiter frames is detected.

Frame removal mechanism for token ring networks

Method and apparatus for operating a digital communication network to avoid congestion by detecting load conditions at intermediate stations exceeding an overload condition, flagging information packets associated with those streams of traffic accounting for more than their fair share of throughput at such overloaded stations, and reducing at the end systems the throughput of those streams of traffic of which more than a predetermined fraction of the information packets received by the end systems are flagged.

System for avoiding network congestion by distributing router resources

Frame processing apparatus, and a related method for its operation, for use in a station connected to a token ring network, to ensure rapid stripping of frames from the network without reference to source addresses in the frames, and in spite of the possible presence of extraneous no-owner frames on the network. The adverse effects of extraneous no-owner frames are avoided by any of three techniques. First, transmitted information frames are preceded by a start strip delimiter frame and followed by an end strip delimiter frame. The process strips all incoming frames (except tokens and ring initialization frames, which are specially handled), but does not count the stripped frames until the start strip delimiter frame is detected. Therefore, extraneous frames preceding the transmitted information frames will be stripped but not counted, and all of the transmitted frames will be stripped. In another approach, an estimated stripping time is used to terminate stripping. Frame counters are not then needed and extraneous frames will be stripped prior to the desired information frames. A third approach is to preset the transmitted frame count to some selected value, so that more frames will be stripped than were transmitted. Thus, preceding extraneous frames will be stripped, but the end strip delimiter will still terminate stripping and preclude overstripping.

Frame removal mechanism for token ring networks using one or more start

A system for stripping frames transmitted by a station on a token ring network is disclosed. During operation of the system, the station receives a grant of permission to transmit onto the network. In an example embodiment, the grant of permission is a token. After receipt of the grant of permission to transmit, the station transmits one or more information frames onto the network. Upon transmission of the information frames, the station stops forwarding frames received from the network, thus removing received frames from the network. Removing received frames from the network is referred to as `stripping`. Following transmission of the information frames, the station transmits an end strip delimiter frame onto the network. Upon receipt of the end strip delimiter frame, the station terminates stripping. In an example embodiment, the system is used in a bridge station, the bridge station connecting a first network with a second network.

Frame removal mechanism using end delimiter frames for token ring

Method and apparatus for operating a digital communication network to avoid congestion by detecting load conditions at the routers exceeding their knee capacities, flagging information packets associated with those streams of traffic accounting for more than their fair share of throughput at such overloaded routers, and reducing at the end systems the throughput of those streams of traffic for which more than a predetermined fraction of information packets received by the end systems are flagged.

Congestion avoidance scheme for computer networks

A system for stripping frames transmitted by a station on a token ring network is disclosed. During operation of the system, the station receives a grant of permission to transmit onto the network. In an example embodiment, the grant of permission is a token. After receipt of the grant of permission to transmit, the station transmits one or more frames onto the network. The station counts the number of frames transmitted onto the network. The count of frames transmitted onto the network is the `frame count`. Upon transmission of the frames, the station stops forwarding frames received from the network, thus removing received frames from the network. Removing received frames from the network is referred to as `stripping`. Following transmission of the information frames, the station counts the number of frames stripped from the network. The count of frames stripped from the network is the `strip count`. When the strip count equals the frame count, the station terminates stripping. In an example embodiment, the system is used in a bridge station, the bridge station connecting a first network with a second network.

Frame removal mechanism using frame count for token ring networks

A station transmits a sequence of one or more frames on a token ring, keeping count of the frames transmitted. At the end of the transmitted frame the station originates onto the ring one or more coded marker frames and finally transmits a token. After the station transmission is begun, the station strips from the ring all the frames it receives, decrementing its count for each properly stripped frame, until either its count is reduced to zero or one of its marker frames is detected.

Frame removal mechanism using count of frames and delimiter frame for

A ring purging station for a token-ring network is disclosed. The station performs purging operations to remove no-owner frames and frame remnants from the network. The station begins a purging operation by detecting the token on the network and removing it. The station then begins stripping all frames and remnants of frames that it receives from the network, and transits one or more purge marker frames. When the station detects one of the one or more purge marker frames it transmitted, it ends the purging operation, and releases the token back onto the ring. In this way no-owner frames and frame fragments are removed from the network, while the ring is otherwise normally operating. In an embodiment of the invention, a sequence number is associated with each purging operation, included in the purge marker frame(s), and verified upon receipt of the purge marker frame(s). The station also corrects multiple token conditions when a multiple token condition is detected during a purging operation. A further aspect of the invention is an election method for selecting a purging station from the stations on the ring.

Growing community of inventors

Maynard, MA, United States of America

K K Ramakrishnan