1. PTP (IEEE 1588)
PTP is a time synchronization protocol.
It compensates for the internal processing latency of network devices by periodically sending synchronization messages (Sync, Follow_up, etc.) in the network and using hardware timestamping.
Physical meaning: To provide all nodes in the network with a unified, high-precision clock reference (Grandmaster Clock).
Precision: Reaching sub-microsecond or even nanosecond levels, far exceeding traditional NTP.
2. TSN (IEEE 802.1 series standards)
TSN is a subset of Ethernet standards.
It's not a protocol, but a "toolbox." It modifies standard Ethernet at the data link layer (L2), introducing the following key mechanisms:
Clock synchronization (802.1AS): This is actually a "customized version" of PTP in TSN.
Traffic scheduling (802.1Qbv): Time-aware shaper (TAS) acts like a traffic light, allowing only high-priority traffic to pass through specific time slots.
Frame preemption (802.1Qbu): Important data needs to be transmitted, while ordinary data is "segmented" and retransmitted to make way for urgent tasks.
| characteristic | PTP (IEEE 1588) | TSN (IEEE 802.1) |
| nature | Time alignment tool | Deterministic data transmission system |
| Main tasks | Make everyone's time consistent | Ensure important data arrives on time |
| Standard | IEEE 1888 (Instrumentation Standard) | IEEE 802.1 (Ethernet standard) |
| hierarchy | Application layer/protocol layer | Physical layer/Data link layer |
| Dependency | Independent operation | Strongly dependent on PTP (especially scheduling functionality). |
PTP is responsible for "aligning with the past", while TSN is responsible for "managing the future".
In the Industrial Internet, PTP provides a unified timeline, while TSN plans the "departure timetable" for each data packet on this axis. Without the high-precision synchronization of PTP, TSN's Time Slot Control (TAS) will cause data collisions due to time deviations.
