OTN Shim Layer for Rapid Circuit Provisioning
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Solution Overview
Problem
Current Optical Transport Networks (OTN) face challenges in rapid circuit provisioning and mesh restoration due to dropped signaling messages, which hinder carrier-grade restoration times, especially when using in-band signaling protocols like OSRP, as they rely on timers and can result in network restoration performance above the required standards.
Innovation Solution
A shim layer is introduced between OTN messaging and signaling/routing protocols, implementing a fast 'OTN Setup' protocol that buffers outgoing messages during re-framing, ensuring no message loss and allowing the network to re-frame without dropping signaling frames, thus enabling faster connection changes and mesh restoration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If in-band signaling protocols like OSRP are used for OTN circuit provisioning, then the network can dynamically establish and restore connections, but signaling messages are dropped during re-framing operations causing restoration times to exceed carrier-grade requirements
Solution Approach 1:
The system performs preliminary actions by buffering outgoing signaling messages before re-framing operations begin. This preliminary buffering ensures that no messages are lost during the critical re-framing period, allowing the network to restore connections faster than traditional timer-based protocols while maintaining message integrity.
Solution Approach 2:
A shim layer is introduced as an intermediary component between the OTN framer and the control plane. This intermediary manages the buffering and release of signaling messages, decoupling the re-framing operations from the signaling protocol timeline. The shim layer acts as a mediator that coordinates message flow during connection changes, enabling sub-100ms restoration without message loss.
2Reliability
If traditional timer-based retransmission protocols are used, then message loss during re-framing can be handled, but operational complexity increases and restoration speed decreases
Solution Approach 1:
The harmful element of timer-based retransmission logic is extracted from the signaling protocol itself and replaced with a simpler buffering mechanism in the shim layer. By removing the complex timer management and retransmission state machines from the protocol stack, the system achieves message delivery reliability through straightforward buffering and release operations, significantly reducing operational complexity.
3Speed
If rapid circuit provisioning is implemented without message buffering, then connection setup speed increases, but signaling messages are dropped during re-framing requiring retransmission
Solution Approach 1:
The system dynamically adjusts the timing of message release based on the re-framing state. During active re-framing operations, messages are held in the buffer; once re-framing is complete, messages are released for transmission. This dynamic control allows rapid connection provisioning while preventing message loss during the critical re-framing window, achieving both speed and reliability.
Data Source
AI summary
The present disclosure provides systems and methods for rapid circuit provisioning in Optical Transport Networks (OTN) using signaling and routing protocols thereby enabling fast mesh restoration. The present invention utilizes a shim layer between OTN messaging (e.g., GCC or High-Level Data Link Control (HDLC)) and the associated signaling and routing protocol (e.g., OSRP, GMPLS, etc.). If an ODUk Connection CTP or TTP needs to be created, the shim layer runs a fast “OTN Setup” protocol, while buffering out going OTN messages. Incoming messages are still processed and do not require additional buffering. The purpose of the OTN Setup protocol is to allow the OTUk to re-frame on its client ODUk, while buffering out-going messages. When re-framing completes, buffers are released and the OTN messaging resumes without dropping any of the signaling frames.