Abstract
A mechanism is disclosed for maintaining path symmetry of Precision Time Protocol (PTP) message exchanges in a packet switched network. Each network node along a PTP packet path maintains a dedicated PTP Media Access Control (MAC) Address Steering Table that is separate from conventional data plane forwarding and MAC learning tables. PTP packets are identified by User Datagram Protocol (UDP) port 319 for event messages and UDP port 320 for general messages. Upon receiving a forward direction PTP packet from a PTP Grandmaster (GM) toward a Telecom Boundary Clock (T-BC), each node records the source MAC address, source Internet Protocol (IP) address, and ingress port identifier in the PTP MAC Address Steering Table. When a reverse direction PTP packet such as a Delay_Request arrives at the node, the node forwards the packet through the previously learned port, independent of dynamic routing decisions including Equal Cost Multi-Path (ECMP) load balancing. This ensures that forward and reverse PTP packets traverse identical paths, eliminating timing asymmetry and improving PTP Time Error (TE) performance.
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.
Recommended Citation
Anonymous, "Ensuring Symmetric Path Forwarding of PTP Packets Using a Dedicated PTP MAC Address Steering Table", Technical Disclosure Commons, ()
https://www.tdcommons.org/dpubs_series/10419