Experimental Physics and
Industrial Control System

Michael Davidsaver via Tech-talk <[email protected]> · Wed, 22 Jan 2020 11:24:31 -0800

On 1/22/20 8:18 AM, Denise Finstrom via Tech-talk wrote:
> 
> Hello,
> 
> Is there an equivalent to EPICS_CA_MCAST_TTL for the pvAccess protocol?

There isn't one.  PVA doesn't (yet) support search by mcast.

Were you able to make this work with CA?  What does your network topology look
like?  (how many hops)  Did you encounter any problems?

Adding this was a project of mine a few years ago.  I've actually never been
certain that it would work at scale since I don't have access to a large
network with mcast routing enabled for testing.  Nor have I had any feedback
from users until now.  So adding this feature to the PVA protocol code hasn't
been a priority for me.

> We are attempting to use multicast for PV search and haven't found a way to change TTL values when using pvAccess. When we set EPICS_PVA_ADDR_LIST to a multicast address, the multicast goes out with a TTL of one and doesn't get routed to other subnets. We are successfully using multicast for PV search with the CA protocol and EPICS_CA_MCAST_TTL. We are looking to do the same with pvAccess, but the EPICS_PVA_MCAST_TTL environment variable doesn't seem to exist. We are using base-7.0.3.1. Any advice would be appreciated.
> 
> Thanks,
> 
> Denise

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System