Lawo: PTP overview setup and guide

This guide from Lawo, provides good material and guidance on how to setup PTP on your AES67 / ST2110-30 network

https://lawo.com/ip-networking-guide/

Some switches support PTP in order to increase clock accuracy. They can work in two modes: transparent and boundary clock.

The switches running in transparent clock mode measure the time the PTP packets spend travelling through the switch and add a compensation value into the packets to account for that time. This increases the accuracy of PTP time. In this mode all slaves communicate directly with the GM (Grandmaster), which – depending on the number of slaves – might cause a substantial amount of load on the GM.

In boundary clock mode the switch participates in the grand master election process and presents itself as PTP master on any switch port that does not have “better” master attached to it. This mode alleviates much of the processing load from the grandmaster (now only the switch request time directly from the grandmaster) and thus allows for bigger networks with more PTP clients

For Clear-Com systems running IPT antennas for FreeSpeak II or FS Edge , a even tighter tolerance is required to allow for RF roaming

For good roaming IPT antennas require a tolerance of 100ns (± 0.1 µs)

The table below shows the values required for good FreeSpeak II / FS Edge roaming using IPT antennas

PTP parameters

Value (range)

Performance

PTP parameters

Value (range)

Performance

Offset from the master clock (OFM)

± 100 ns

± 0.1 µs

Excellent

 

± 500 ns

Potential for roaming issues

 

 

± 1,000 ns

± 1 µs

Issues with roaming likely

 

 

>± 1,000 ns

Cannot roam between transceivers and intermittent loss-of-lock issues

 

Lawo conclusion :

Since the ST2059-2 (ST2110 PTP) profile uses an “aggressive” timing, in order to achieve the use of a high performance grand master, along with hybrid mode and / or boundary clock ethernet switches are recommended for larger systems.