RE: pvaRepeater [SEC=UNOFFICIAL]

["STARRITT, Andrew via Tech-talk" <tech-talk at aps.anl.gov>]

Hi Ralph,
Thank-you for the information.
Cheers
Andrew

UNOFFICIAL

From: Tech-talk <tech-talk-bounces at aps.anl.gov> On Behalf Of Ralph Lange via Tech-talk
Sent: Friday, 13 March 2026 8:49 PM
To: EPICS Tech Talk <tech-talk at aps.anl.gov>
Subject: Re: pvaRepeater [SEC=UNOFFICIAL]

 

CAUTION, EXTERNAL EMAIL: This message has come from outside of ANSTO. Do not take action, click links or open attachments unless you trust the source of this message and know the content is safe. Report spam and phishing using the Report Message button or if unsure, forward this message to servicedesk at ansto.gov.au as an attachment.

 

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