Multicast time synchronization - Metasys - LIT-12013352 - M4-SNE10500-0 - M4-SNE10501-0 - M4-SNE11000-0 - M4-SNE11001-0 - M4-SNE110L0-0 - M4-SNE110L1-0 - M4-SNE22000-0 - M4-SNE22001-0 - Supervisory Device - SNE10 Network Engine - SNE11 Network Engine - SNE22 Network Engine - SNE Supervisory Network Engine - 12.0

SNE Commissioning Guide

Product name
SNE10 Network Engine
SNE11 Network Engine
SNE22 Network Engine
SNE Supervisory Network Engine
Document type
Commissioning Guide
Document number
Revision date
Product status

Multicast time synchronization is the Johnson Controls implementation of SNTP w32time with Multicast capabilities and RFC-2030 compliance. Multicast is the most commonly used time synchronization option for Metasys sites. This method delivers the same features as the Windows method, but also provides improved Metasys time synchronization between the Site Director and supervisory devices. A time server provides the time to the Site Director, and the Site Director in turn multicasts the time to all supervisory devices on the Metasys network. By default, the server's operating system synchronizes with the external time server once every seven days.

When a supervisory device first reports to the Site Director, it polls the Site Director for the current time and matches its time with the Site Director time. By default, every 5 min the Site Director broadcasts the current time to all supervisory devices. You can change this duration, called the Multicast Heartbeat Interval, from one to 255 min. If a particular device time differs 1.5 seconds or more from the Site Director time, the device adjusts its time to match. Additionally, if the Site Director time changes by more than 1 to 1.5 seconds, it sends out a Multicast time message to all devices within 2 seconds of the change. This time synchronization method reduces the time interval in which devices are out of sync with the SNTP time server.
Note: Use Windows Time Sync for the SNx engines.

Multicast time synchronization requires that all Ethernet routers on the site support Multicast routing (Internet Group Multicast Protocol [IGMP]) because the Multicast time message crosses routers. To implement Multicast synchronization across routers, you may require assistance from the customer's IT department.