Path Delay Asymmetry Distribution in RSVP-TE Networks
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Solution Overview
Problem
In connection-oriented communications networks, existing methods for distributing path delay data are inefficient, particularly in optical communications networks where asymmetry in propagation delay can impact time synchronization, requiring costly and time-consuming manual calibration and causing scalability issues with flooding protocols like OSPF.
Innovation Solution
A method for distributing path delay data across a connection-oriented communications network involves nodes receiving and sending signalling messages with path delay data, minimizing data sent over the control plane, using RSVP-TE control plane signalling to forward data between nodes involved in a traffic path, allowing for more accurate time synchronization and improved network scalability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manual calibration of path delay asymmetry is performed node-by-node, then time synchronization accuracy is improved, but deployment cost and time consumption increase significantly
Solution Approach 1:
The network nodes automatically perform path delay asymmetry measurements and distribute the data themselves without requiring manual calibration. The ingress node initiates measurements and nodes along the path automatically collect and forward asymmetry data, making the system self-configuring and eliminating labor-intensive manual deployment
Solution Approach 2:
Path delay asymmetry data is collected and distributed in advance during connection setup or network reconfiguration events, before actual time synchronization operations begin. This preliminary data collection ensures that synchronization can immediately use accurate asymmetry values without requiring ongoing manual updates
2Loss of information
If flooding protocols like OSPF are used to distribute asymmetry data, then data distribution coverage is improved, but network scalability deteriorates due to large data volumes
Solution Approach 1:
Instead of flooding asymmetry data to all network nodes, the invention distributes path delay asymmetry data only to the specific egress nodes that need it for their respective traffic paths. Each node receives only the local asymmetry data relevant to its function, minimizing unnecessary data transmission and improving scalability
Solution Approach 2:
The asymmetry data distribution is segmented by traffic path, with each path's asymmetry data independently collected and distributed only to the relevant egress node. This segmentation prevents the exponential data growth that would occur with network-wide flooding protocols
3Measurement precision
If path delay data is extensively distributed across the network, then synchronization accuracy is improved, but control plane data transmission load increases
Solution Approach 1:
The invention extracts only the essential path delay asymmetry data from the complete path delay information and distributes only this extracted subset to egress nodes. By taking out only the necessary asymmetry component rather than distributing all path delay data, the control plane load is minimized while maintaining synchronization accuracy
Data Source
AI summary
A connection-oriented communications network comprises a plurality of interconnected nodes. A traffic path can be set up across the network. Path delay data is obtained for the traffic path by using control plane signalling messages (e.g. a Resource Reservation Protocol-Traffic Engineering, RSVP-TE signalling message) between nodes of the traffic path. The path delay data can be path delay asymmetry data indicative of an asymmetry in path delay between a forward transmission direction and a reverse transmission direction of the traffic path. Each intermediate node along the traffic path can form a signalling message for forwarding to the downstream node which includes one or more values of path delay incurred by that node, or an accumulated path delay value. The path delay can result from one or more of mapping delay, Forward Error Correction (FEC) coding and propagation delay.