Digital Equipment Corporation

Digital Equipment Corp., Patent Law Group

Rajendra K Jain

K K Ramakrishnan

Henry S Yang

Barry A Spinney

Dah-Ming Chiu

Richard L Szmauz

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

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

Ideal for use in high-speed wide-area networks, such as HDLC as defined in ISO Standard 3309, a strong framing method for data packets significantly improves undetected error probability. In a run-length code type data communication scheme, wherein frame delimiter strings, abort strings and idle strings, are transmitted as control symbols, the method includes providing the frame delimiter string as a multi-symbol construct for delimiting the transmitted data, providing the abort strings and idle strings to respectively include minimum run lengths which are substantially longer than the individual symbols in the multi-symbol construct, transmitting data with control symbols as a bit sequence, and receiving and analyzing the transmitted data at the data-receiving device to detect the presence of bit errors.

Strong framing protocol for HDLC and other run-length codes

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 packet data communication system employs a congestion avoidance method in which each node measures the round-trip delay occurring when it sends data to a destination and receives an acknowledgement. This delay is measured for different load levels, and a comparison of these delays is used to determine whether to increase or decrease the load level. The load level can be adjusted by adjusting the window size (number of packets sent in to the network) or by adjusting the packet rate (packets per unit time). The objective is operation at the knee in the throughput vs. traffic curve, so that the data throughput is high and the round trip delay is low. Control is accomplished at each node individually, without intervention by the router or server, so system overhead is not increased.

Delay-based congestion avoidance in computer networks

A token ring network includes a plurality of stations interconnected to transmit frames containing information. A station may originate a frame transmission if it has information to transmit and if it is holding a token. A frame includes the information and a token request flag initialized to a selected condition. While one station is originating transmission of the frame around the network, if another station needs to transmit a frame, that station conditions the token request flag to another predetermined condition. The originating station receives the frame and examines the token request flag. If the token request flag has the predetermined condition, it transmits the token over the network to permit another station to originate a frame transmission. Thus, unless another station needs to transmit a frame, as indicated to the originating station by the condition of the token request flag, the originating station may continue to transmit, and so the time an originating station may transmit is not limited to any arbitrary time period.

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Sudbury, MA, United States of America

Rajendra K Jain