Re: pvaRepeater [SEC=UNOFFICIAL]

[Ralph Lange via Tech-talk <tech-talk at aps.anl.gov>]

On Fri, 13 Mar 2026 at 04:23, STARRITT, Andrew via Tech-talk <tech-talk at aps.anl.gov> wrote:

Why is there no pvaRepeater?

It's not needed anymore.

CA needed all clients to receive IOC (UDP) beacons, as that was the only way to detect connection loss. The caRepeater is handling this on every client host (by receiving and redistributing to local clients).

PVA has changed the implementation of connection check and validation, which now happens entirely on the data circuit (TCP). Beacons are still used, but only for "new server up" announcements.

To avoid needing a repeater (for multiple clients) and/or network configuration tricks (for multiple servers), PVA requires any peer to resend received unicast UDP packages on a dedicated local multicast address: i.e., any PVA client or server acts as a repeater when needed.

Cheers,
~Ralph

https://docs.epics-controls.org/en/latest/pv-access/protocol.html#summary

https://docs.epics-controls.org/en/latest/pv-access/Protocol-Messages.html#cmd-beacon-0x00