Optical Network Device Fast Reroute Without Slot Reservation
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Solution Overview
Problem
Optical networks face challenges in quickly rerouting traffic due to slow exchange of control plane signaling messages, which can lead to delays in bypassing failed links, especially in applications requiring real-time data delivery like VoIP and video conferencing.
Innovation Solution
Implementing a method where optical network devices store forwarding rules that include both primary and backup slots, allowing for immediate rerouting of data units to virtual slots, which correspond to physical slots, without reserving the physical slot, enabling fast re-routing when a downstream segment becomes non-operational.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If control plane signaling messages are exchanged to reroute traffic, then traffic can be redirected to backup paths, but the rerouting process is slow and causes delays
Solution Approach 1:
The patent pre-establishes backup forwarding equivalence classes (FECs) and their associated backup paths before failures occur. When a failure is detected, the system immediately switches to the pre-configured backup FEC without needing to exchange control plane signaling messages for path computation, thereby eliminating rerouting delays while maintaining reliability
Solution Approach 2:
The patent segments the forwarding equivalence class into primary and backup FECs, each with dedicated forwarding tables. This segmentation allows the system to maintain separate forwarding paths and switch between them instantly based on operational status, resolving the contradiction between having rerouting capability and avoiding rerouting time
2Speed
If physical slots are reserved for backup paths, then fast rerouting is enabled, but slot availability is reduced and resource utilization decreases
Solution Approach 1:
The patent creates virtual copies of slot identifiers for backup paths without reserving actual physical slots. The backup FEC references virtual slot identifiers that map to the same physical slots used by primary paths, enabling fast rerouting through virtual slot allocation while preserving physical slot availability for multiple paths
Solution Approach 2:
The patent makes physical slots serve multiple functions by allowing them to be shared between primary and backup paths through virtual slot mapping. A single physical slot can be referenced by both a primary FEC and multiple backup FECs, enabling the system to achieve fast rerouting capability without dedicating separate physical slots for backup purposes
Data Source
AI summary
An optical network device re-routes traffic from a path to a backup path in response to determining that a downstream segment of the primary path is not operational. The optical network device receives traffic on a slot of an optical fiber. For each data unit in the traffic, the optical network device determines, based on receiving the data unit on the slot and based on a flow identifier specified in the data unit, that a given path is associated with the data unit. If a downstream segment of the given path is not operational, the optical network device routes the data unit onto a backup path instead of routing the data unit along the given path. Bandwidth is not reserved for the backup path.