# US 6,990,071 B2 · Method for reducing fetch time in a congested communication network > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 6,990,071 B2 - Document ID: US6990071B2 - Status: Granted - Kind: B2 - Application number: 09/846,174 - Filed: 2001-04-30 - Published: 2002-04-25 - Granted: 2006-01-24 - Earliest claimed: 2000-03-30 - Assignees: Network Physics, Inc. - Inventors: Ian Adam; Tomas J. Pavel; Han C. Wen; Minh Duong-van; Mark Crane - Web page: https://patentgrep.com/patent/US6990071B2 ## CPC - H04L 12/5602: {Bandwidth control in ATM Networks, e.g. leaky bucket} - H04Q 11/0478: {Provisions for broadband connections} - H04L 2012/5635: {Backpressure, e.g. for ABR} - H04L 2012/5636: {Monitoring or policing, e.g. compliance with allocated rate, corrective actions} - H04L 2012/5647: {Cell loss} - H04L 2012/568: {Load balancing, smoothing or shaping} - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - H04Q: SELECTING (switches, relays, selectors H01H; wireless communication networks H04W) ## Abstract Congestion within a communication is controlled by rate limiting packet transmissions over selected communication links within the network and modulating the rate limiting according to buffer occupancies at control nodes within the network. Preferably, though not necessarily, the rate limiting of the packet transmissions is performed at an aggregate level for all traffic streams utilizing the selected communication links. The rate limiting may also be performed dynamically in response to measured network performance metrics; such as the throughput of the selected communication links input to the control points and/or the buffer occupancy level at the control points. The network performance metrics may be measured according to at least one of: a moving average of the measured quantity, a standard average of the measured quantity, or another filtered average of the measured quantity. The rate limiting may be achieved by varying an inter-packet delay time over the selected communication links at the control points. The control points themselves may be located upstream or even downstream (or both) of congested nodes within the network and need only be located on only a few of a number of communication links that are coupled to a congested node within the network. More generally, the control points need only be associated with a fraction of the total number of traffic streams applied to a congested node within the network. ## Claims ### Claim 1 A method of congestion control in a communication network, comprising rate limiting packet transmissions over selected communication links within the network at control nodes thereof; and modulating the rate limiting according to buffer occupancies at the control nodes; wherein the rate limiting comprises modulation of packet bandwidths of traffic streams utilizing the selected communication links and the modulation of packet bandwidths is performed dynamically in response to measured network performance metrics. ### Claim 2 (depends on 1) The method of claim 1 wherein the network performance metrics are selected from the list including: throughput of the selected communication links input to the control nodes and/or buffer occupancy level at the control nodes. ### Claim 3 (depends on 1) The method of claim 1 wherein the network performance metrics are measured according to at least one of: a moving average of the measured quantity, a standard average of the measured quantity, or another filtered average of the measured quantity. ### Claim 4 (depends on 1) The method of claim 1 wherein the modulation of packet bandwidths is achieved by varying an inter-packet delay time over the selected communication links at the control nodes. ### Claim 5 (depends on 1) The method of claim 1 wherein the control nodes are located upstream of congested nodes within the network. ### Claim 6 (depends on 1) The method of claim 1 wherein the control nodes are located downstream of congested nodes within the network. ### Claim 7 (depends on 1) The method of claim 1 wherein the control nodes are located on only a few of a number of communication links that are coupled to a congested node within the network. ### Claim 8 (depends on 1) The method of claim 1 wherein the control nodes are associated with only a fraction of a total number of traffic streams applied to a congested node within the network. ### Claim 9 (depends on 1) The method of claim 1 wherein the modulating according to buffer occupancies is performed according to a modulation function that is linear in nature. ### Claim 10 (depends on 1) The method of claim 1 wherein the modulating according to buffer occupancies is performed according to a modulation function that is quadratic in nature. ### Claim 11 (depends on 1) The method of claim 1 wherein the modulating according to buffer occupancies is performed according to a modulation function that is step-wise in nature. ### Claim 12 A communication network comprising a number of nodes interconnected with one another through one or more communication links, a first one of the nodes being configured to control packet loss within the network by rate limiting packet transmissions over selected ones of the communication links, such rate limiting being modulated according to buffer occupancy at the first one of the nodes; wherein the rate limiting is modulated according to a modulation function that is one of linear, quadratic or step-wise in nature; wherein the rate limiting comprises modulation of packet bandwidths of the traffic streams utilizing the selected communication links. ### Claim 13 (depends on 12) The network of claim 12 wherein modulation of the rate limiting is set empirically according to network conditions. ### Claim 14 (depends on 12) The network of claim 12 wherein the rate limiting is performed dynamically in response to measured network performance metrics. ### Claim 15 (depends on 14) The network of claim 14 wherein the network performance metrics are selected from the list including: throughput of the selected communication links input to the control nodes and/or buffer occupancy level at the control nodes. ### Claim 16 (depends on 14) The network of claim 14 wherein the network performance metrics are measured according to at least one of: a moving average of the measured quantity, a standard average of the measured quantity, or another filtered average of the measured quantity.