Forwarding Plane Port State Tables for Fast Reroute
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Solution Overview
Problem
Conventional network elements take too long to recover from port failures, leading to increased downtime and packet loss due to inefficient detection and distribution of port states, relying heavily on management and control plane software for rerouting.
Innovation Solution
Implementing a mechanism to maintain port state tables within the forwarding plane of network elements, allowing for fast and efficient detection and distribution of port states, enabling seamless failover without dynamic assistance from management or control plane software, using a computer-readable medium with instructions for fast rerouting of unicast packets to available ports within a multi-link trunk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional network elements use management and control plane software to handle port failures, then routing decisions can be made with full information, but the recovery time increases significantly and packet loss increases
Solution Approach 1:
The patent segments the network element into two independent planes: the control plane (management software) and the forwarding plane (hardware). The forwarding plane maintains its own port state tables and can make autonomous routing decisions without waiting for control plane software processing, enabling fast failover while the control plane handles long-term management tasks.
Solution Approach 2:
The forwarding plane pre-populates port state tables with routing information and maintains port state information in advance. When a failure occurs, the forwarding plane can immediately use this pre-prepared information to reroute traffic without waiting for the control plane to process and distribute updates, achieving sub-10-millisecond recovery times.
2Device complexity
If traffic is concentrated on a single designated alternate port for failover, then routing simplicity is maintained, but the alternate port becomes overloaded and network performance degrades
Solution Approach 1:
The patent implements dynamic load distribution across multiple alternate ports in the multi-link trunk. Instead of statically designating one alternate port, the forwarding plane dynamically selects from multiple available ports based on current port states and traffic conditions, distributing the load to prevent any single port from becoming overloaded while maintaining routing simplicity through the MLT abstraction.
3Quantity of substance
If port state information is not maintained in the forwarding plane, then device memory usage is reduced, but failover detection and response time increases
Solution Approach 1:
The forwarding plane maintains its own port state tables and performs autonomous failure detection and routing decisions without requiring continuous queries to the control plane or management software. This self-service capability enables the forwarding plane to independently detect port failures and reroute traffic immediately, achieving fast failover while using only the memory required for the port state tables in the forwarding plane.
Data Source
AI summary
A method, apparatus and computer program product for providing fast reroute of a packet is presented. A unicast packet is received by an FDU in a data plane of a network element and a destination is determined for the packet. A lookup is performed in a port state table maintained by the FDU to determine an available local port that is in an UP state for the destination, and if no local port is UP, then a lookup is performed in the port state table to determine an available remote port that is in an UP state for the destination. If a port in the UP state cannot be determined for the unicast packet, then the packet is dropped.