TDM Pseudowire Circuit Emulation Engine for Network Outage Resilience
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Solution Overview
Problem
Current TDM pseudowire implementations, such as SAToP, face challenges in quickly restoring connectivity during network outages and delays, leading to prolonged downtime for customer edge devices due to the need to restore Layer 1 and Layer 2 connectivity.
Innovation Solution
A provider edge node that includes a receiver, physical interface, and circuit emulation engine, which transmits frames with an idle pattern in the payload and a predefined framing pattern among the framing bits during network errors, maintaining the physical layer of the customer edge device and reducing restoration time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the provider edge node transmits notification of network delay and loss to the customer edge device according to RFC 4553, then the customer edge device can detect the network issue, but the physical layer connectivity must be restored first which causes prolonged outage time
Solution Approach 1:
The patent applies preliminary action by pre-configuring the physical layer interface to remain in an operational state even during network outages. The framing engine continues to generate and transmit TDM frames with proper framing patterns during packet loss events, maintaining the physical layer connection state before actual service restoration is needed. This allows the system to be prepared in advance, eliminating the need for time-consuming Layer 1 restoration procedures.
2Reliability
If the customer edge device restores Layer 1 connectivity first upon receiving outage notification, then proper connectivity can be reestablished, but the restoration process takes many seconds
Solution Approach 1:
The patent implements continuity of useful action by ensuring that the framing engine continuously generates and transmits TDM frames with proper framing patterns even during network outages. This continuous transmission maintains the physical layer connection state and prevents the need to interrupt and restart the connection restoration process, enabling seamless service recovery without time-consuming Layer 1 re-establishment procedures.
3Loss of information
If the provider edge node stops transmitting during network errors, then packet loss is avoided, but the customer edge device physical layer becomes non-operational requiring full restoration
Solution Approach 1:
The patent applies segmentation by separating the transmission function into two independent components: the packet-based network transmission layer and the TDM framing layer. During network outages, the packet transmission can be suspended or experience loss without affecting the continuous TDM framing transmission at the physical layer. This segmentation allows the framing layer to maintain connection state independently of packet layer issues, preventing the need for full connection restoration.
Data Source
AI summary
Various exemplary embodiments relate to a provider edge node and a related method. The provider edge node may include a receiver that receives at least one packet transmitted over a TDM pseudowire using a structure-agnostic transmission mechanism. The provider edge node may also include a physical interface configured to output frames to a corresponding customer edge (CE) device and a machine-readable storage medium that stores a TDM framing type corresponding to the physical interface. Finally, the provider edge node may include a circuit emulation engine that, during periods in which a network error has occurred, transmits a plurality of frames to the CE device over the physical interface. A TDM data payload of each frame may include an idle pattern, while a group of framing bits of the plurality of frames may define a framing pattern corresponding to the TDM framing type stored for the physical interface.