Interpreting Livewire clock SYNC data

Updated by Bryan Jones

For this example, we are using an xNode. Several products can display sync data. Regardless of the product, the principles and information are the same. For example, an iQ console will show this in a different format; however, the information as to the identification of the master and the Delta and Sigma numbers apply as described here.

Sync: This is the same as the front panel. Solid SYNC represents proper synchronization with the master clock. Flashing or "---" indicates an error or that the node is still syncing.

Variations of the Sync: indicator.

Your nodes will almost always show SYNC. If you find a node that shows "Internal Clock" (shown in the graphic below), then you have found the MASTER. This node is using its internal oscillator to produce a clock signal (in this case) for both PTP and Livewire.

PTP is the clock mechanism used for AES67 and is outside of the scope of this document.

Yours might indicate, "This unit is a master for Livewire." If you are not using AES67, that indication would be perfectly normal.

Master Clock source information

Slave to: Livewire/AC050272 p5 192.168.2.114:7000 shows us that we are a slave to a clock originating from the IP Address 192.168.2.114 and that node has a clock priority of 5 (noted by the "p5" before the IP Address)

The delta [δ -0.1µs] is the phase error. Delta shows the difference between the local clock on the node compared to the clock received from the master.

Note that when we say "clock," we are referring to a "rate" clock and not a clock that shows the time of day. Think of it as a metronome for music.

Sigma [σ 0.2µs] is a variation of the delta. It shows how noisy the signal is. Described another way, it is a measure of the timing from packet to packet.

Those two numbers are expected to be around ±1.0 µs (microsecond).  

Frequency Adjustment [+0.72ppm] is how much the local clock frequency is adjusted to match the received network clock. The nodes have oscillators with +/-2.5ppm tolerance. We expect up to 10ppm adjustment range [±5.0ppm]. +0.72 ppm is very good. Ppm is parts per million. +1ppm in the case of a 1MHz clock will be 1000001Hz.

More information on Delta/Sigma modulation is available at http://en.wikipedia.org/wiki/Delta-sigma_modulation.

Identifying a Livewire Master

More recent versions of products display the actual IP Address of the Master. Some older versions would only show the MAC address of the Master. Once a MAC ADDRESS is known for the Master Livewire clock, an ARP table can be used to identify the IP address associated with that MAC address.  

Windows will cache the MAC addresses for all known devices cross-referenced to the IP address if the PC has communicated with that device. For example, a computer that is running iProbe will discover and “touch” all devices on the Livewire network. So would a computer running Pathfinder. From one of those computers, open a command prompt and then type the following command:

C:\> arp -a

You will see a list of MAC addresses (shown as Physical Address) and their associated IP Address.

Pro Tip - The MAC Address for all Axia devices start with either 00-50-C2 or 58:50:AB.

How did we do?