TCP Adaptation for Variable Jitter in Cable Modems

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Solution Overview

Problem

Transmission Control Protocol (TCP) mechanisms fail to effectively adapt to variable jitter conditions in communications channels, leading to suboptimal throughput in network topologies like those between a cable modem termination system (CMTS) and cable modems (CMs), where jitter can cause ACK/NACK timeouts even with successful data reception.

Innovation Solution

Monitoring CMTS-CM communication links for jitter levels exceeding thresholds, the TCP connections are adapted to operate non-normatively by increasing downlink and uplink throughput, ignoring or modifying ACK/NACK signals to use larger data packet sizes and adjust transmission parameters accordingly.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If TCP implements standard congestion avoidance and control algorithms with slow-start mechanism, then TCP connections can maintain stability and reliability, but data throughput becomes suboptimal in high-jitter environments due to excessive conservative packet size adjustments

Engineering Contradiction:

ImproveTCP connection stabilityVSAvoiddata throughput

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent implements dynamic adaptation of TCP packet sizes based on real-time jitter measurements. The system transitions from static TCP parameters to dynamic adjustment where packet sizes are modified according to measured jitter conditions, allowing the connection to optimize throughput while maintaining reliability in variable network conditions

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes TCP protocol parameters (packet sizes, timeouts) based on measured jitter levels. When jitter exceeds thresholds, the system modifies normative TCP behavior by adjusting packet sizes and timing parameters to compensate for jitter-induced delays, thereby maintaining both reliability and throughput

Inventive Principle:

Principle #35Parameter changes

2Reliability

If TCP uses normative slow-start algorithm doubling packet size on ACK, then connection reliability is maintained through conservative growth, but data transmission speed is limited by excessive caution in high-jitter conditions

Engineering Contradiction:

ImproveACK-based congestion controlVSAvoiddata transmission speed

Core Design Contradiction:

ReliabilityVSSpeed

Solution Approach 1:

The patent performs preliminary jitter measurement and assessment before TCP data transmission begins. By measuring jitter characteristics in advance and establishing baseline performance metrics, the system can pre-adjust TCP parameters to account for expected jitter conditions, enabling faster initial packet size growth without compromising reliability

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements feedback mechanisms where jitter measurements continuously inform TCP parameter adjustments. The system monitors jitter levels and uses this feedback to dynamically modify packet sizes and transmission timing, creating a closed-loop control system that maintains both reliability and speed by adapting to real-time network conditions

Inventive Principle:

Principle #23Feedback

3Reliability

If TCP connections operate with standard timeout mechanisms, then reliability is ensured through proper error handling, but throughput suffers from timeout-induced interruptions when jitter causes delayed ACK/NACK reception

Engineering Contradiction:

Improvetimeout-based error handlingVSAvoidthroughput continuity

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent dynamically adjusts TCP timeout values based on measured jitter levels. When jitter increases, the system extends timeout thresholds to account for delayed packet arrivals, preventing false timeout conditions. This dynamic timeout adjustment maintains reliability by properly distinguishing between actual packet loss and jitter-induced delays

Inventive Principle:

Principle #15Dynamics

4Stability of the object's composition

If TCP monitors network conditions and adapts packet sizes normatively, then connection stability is maintained, but the monitoring and adaptation overhead reduces net throughput in high-jitter environments

Engineering Contradiction:

Improveconnection stabilityVSAvoidnet throughput

Core Design Contradiction:

Stability of the object's compositionVSProductivity

Solution Approach 1:

The patent combines jitter measurement functions with existing TCP monitoring mechanisms. By integrating jitter detection into the existing TCP stack and combining it with packet size selection logic, the system eliminates separate monitoring overhead and achieves both stability and throughput optimization through unified processing

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS20230164084A1Adapting TCP in variable jitter environments

Publication Date: 2023.05.25 CHARTER COMM OPERATING LLC

AI summary

Various embodiments comprise systems, methods, mechanisms, and apparatus adapting Transmission Control Protocol (TCP) traffic flows between a cable modem termination system (CMTS) and a plurality of cable modems (CMs) connected thereto via respective CMTS-CM TCP connections supported by respective CMTS-CM communication links. Each CMTS-CM communication link is monitored to determine Quality of Service (QoS) information including jitter information. If the jitter information associated with a particular CMTS-CM communications link exceeds a threshold level (e.g., a level where TCP ACK/NACK reception timeout may occur), then the TCP connection(s) supported by the communication link are adapted to function in a non-normative manner by, illustratively, increasing downlink and/or uplink throughput of TCP connections supported by the communications link irrespective of the usual or normative response of the TCP connection(s).