Source Node Adaptive Routing Control
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Solution Overview
Problem
Adaptive routing in communication networks can cause packets to arrive out of order at the destination, leading to increased traffic load due to retransmissions, as changing routing paths during the lifetime of a flow may result in out-of-order packet delivery.
Innovation Solution
The source node chooses a suitable time point to permit re-routing of packets, ensuring that re-routing does not cause out-of-order delivery by suspending the flow until all prior packets are acknowledged and using permission indications to allow network elements to select different egress interfaces for re-routing, thereby controlling adaptive routing and preventing unnecessary packet retransmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If adaptive routing is used to change routing paths during flow lifetime, then network congestion is reduced and routing flexibility is improved, but packet ordering is violated and retransmissions increase
Solution Approach 1:
The source node performs preliminary actions by suspending the flow before re-routing occurs, ensuring all previously sent packets are acknowledged by the destination node. This preliminary suspension prevents out-of-order delivery when packets are re-routed to a different path, as the suspension point ensures no packets are in-flight that would arrive out of order.
Solution Approach 2:
The system implements feedback mechanisms where the source node receives acknowledgment information from the destination node about packet delivery status. Based on this feedback, the source node determines when it is safe to permit re-routing, ensuring that re-routing only occurs when packet ordering can be maintained.
2Adaptability or versatility
If re-routing is permitted without flow suspension, then routing adaptability is improved, but out-of-order packet delivery occurs and traffic load increases
Solution Approach 1:
The source node performs preliminary suspension of the flow before allowing re-routing to occur. This suspension ensures that all packets sent before suspension are either delivered or can be safely retransmitted, preventing out-of-order delivery when the flow is resumed on a different path.
Solution Approach 2:
The source node takes preliminary anti-action by suspending the flow to prevent the harmful effect of out-of-order packet delivery. This suspension counteracts the potential harm of re-routing before it can cause packet ordering violations, thereby protecting network efficiency.
3Reliability
If flow suspension is implemented before re-routing, then packet ordering is preserved, but re-routing timing is constrained and network response time increases
Solution Approach 1:
The source node uses feedback from the destination node about packet acknowledgment status to determine the optimal timing for suspension and re-routing. This feedback mechanism allows the system to minimize suspension duration while ensuring packet ordering, thereby reducing overall re-routing delay.
Solution Approach 2:
The system implements periodic checking of packet acknowledgment status during flow suspension. This periodic action allows the source node to quickly determine when re-routing can safely occur, minimizing the time lost to suspension while maintaining packet ordering guarantees.
Data Source
AI summary
A method in a network element that includes multiple interfaces for connecting to a communication network includes receiving from the communication network via an ingress interface a flow including a sequence of packets, and routing the packets to a destination of the flow via a first egress interface. A permission indication for re-routing the flow is received in the ingress interface. In response to receiving the permission indication, subsequent packets of the flow are re-routed via a second egress interface that is different from the first egress interface. Further re-routing of the flow is refrained from, until receiving another permission indication.