In-band Control Packets for Network Congestion Detection
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Solution Overview
Problem
Current data center network control methods face challenges in accurately detecting congestion due to noisy signals from metrics like ECN marking, RTT, and available bandwidth estimation, leading to unreliable network visibility and fairness among data flows, and often result in increased packet delays and jitter.
Innovation Solution
The implementation of in-band control packets that are transmitted periodically to monitor network conditions, providing additional signals such as bandwidth credit, queue busyness, prediction of queue build-up, and number of active flows, allowing for better network visibility and fair resource allocation among data flows without requiring switch modifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If packet loss is used to detect network congestion, then congestion detection is achieved, but the detection is late or false due to noisy signals
Solution Approach 1:
The patent applies preliminary action by sending control packets before actual data transmission to probe network conditions in advance. These control packets traverse the network path and provide early warnings of congestion through their own transmission characteristics (delay, loss, ECN marks) before the main data flow encounters problems, enabling proactive congestion avoidance rather than reactive response.
Solution Approach 2:
The patent uses control packets as intermediaries to indirectly assess network congestion state. Instead of directly monitoring data packet loss which is noisy and late, the control packets serve as mediators that carry information about network conditions through their transmission characteristics, providing a cleaner and earlier signal of congestion without being directly affected by data flow variations.
2Reliability
If ECN marking is used to detect congestion, then congestion notification is improved, but the signal becomes noisier due to queue length variations
Solution Approach 1:
The patent applies copying by creating dedicated control packets that replicate the data packet transmission path and characteristics. These control packets copy the same routing, queuing, and processing paths as actual data packets, allowing independent measurement of network conditions without being contaminated by data flow variations. The control packets serve as identical copies that can be reliably measured to infer congestion state.
Solution Approach 2:
The patent extracts congestion detection functionality from the data payload by using separate control packets. Instead of trying to interpret congestion signals within the noisy data traffic, the control packets isolate and extract the congestion detection function, carrying purely diagnostic information that is not mixed with application data variations, thereby achieving cleaner measurements.
3Measurement precision
If RTT is used to estimate available bandwidth, then bandwidth estimation is achieved, but the measurement becomes noisy due to queuing delay variations
Solution Approach 1:
The patent applies preliminary action by measuring control packet transmission characteristics before actual bandwidth utilization occurs. By probing the network with control packets and measuring their delay and loss characteristics in advance, the system can estimate available bandwidth without being affected by the noisy inter-packet interval variations that occur during actual data transmission.
Solution Approach 2:
The patent uses control packets as intermediaries to measure network conditions independently of data flow. The control packets serve as mediators that provide clean measurements of queuing delay and bandwidth availability without being contaminated by application-level traffic patterns, enabling reliable bandwidth estimation through their transmission characteristics alone.
4Reliability
If buffer size is increased in switches to improve network robustness, then network reliability is improved, but packet delays and jitter increase intolerably
Solution Approach 1:
The patent applies preliminary action by enabling congestion detection and response before actual packet loss occurs. Through control packets that probe network conditions in advance, the system can identify congestion early and take corrective action (such as reducing transmission rate or avoiding congested paths) before the buffer becomes full and causes intolerable delays, thereby maintaining network robustness without requiring large buffers.
Solution Approach 2:
The patent implements feedback mechanisms where control packets continuously monitor network conditions and provide information back to the sender. This feedback loop enables dynamic adjustment of transmission parameters based on real-time network state, allowing the system to respond to congestion conditions without requiring large buffers, thus avoiding increased packet delays and jitter while maintaining network robustness.
Data Source
AI summary
There is provided methods and devices for network management. A method includes receiving at least one data flow, transmitting in-band management packet periodically for each of the at least one data flow, receiving in-band acknowledgement packets for each of the at least one data flow, and producing network management data based on received in-band acknowledgement packets. A device includes a processor, and a non-transient computer readable memory having stored thereon machine executable instructions which when executed by the processor configure the device to execute the methods disclosed herein. A system includes a source node, a receiver and a data-plane device, the system configured to execute the methods disclosed herein.