Thanks for the details.
On 1/22/20 12:52 PM, James G Smedinghoff wrote:
> caRepeater did not join the beacon IGMP multicast group,
Ah, yes. This is an oversight. (there had to be something)
> so I used a multicast address for the
> beacons which the client node was already listening to.
From my, likely incomplete, understanding of mcast this seems like it shouldn't work.
Routing packets to a host is certainly necessary, however the IP stack shouldn't pass
them along to a particular socket unless that socket has joined the appropriate group.
Still the path forward is clear. caRepeater needs to process EPICS_CAS_BEACON_ADDR_LIST
and join any mcast groups listed. addAddrToChannelAccessAddressList() from addrList.h can
do most of this.
If you, or someone at FNAL is interested in having a go,
I think the change would be made to 'sock' just above:
https://github.com/epics-base/epics-base/blob/468f965dc2753e7a381dcc09dd9b5656e3149ac2/modules/ca/src/client/repeater.cpp#L520
On 1/22/20 12:52 PM, James G Smedinghoff wrote:
> On 1/22/2020 1:24 PM, Michael Davidsaver wrote:
>> 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?
> Yes, I was able to use multicasts for CA search and beacons by defining environment variables.
> On the client:
>
> EPICS_CA_ADDR_LIST=<multicast address1>
> EPICS_CA_AUTO_ADDR_LIST=NO
> EPICS_CA_MCAST_TTL=20
>
>
> On the IOC:
>
> EPICS_CAS_INTF_ADDR_LIST=<multicast address1>
> EPICS_CAS_BEACON_ADDR_LIST=<multicast address2>
> EPICS_CAS_AUTO_BEACON_ADDR_LIST=NO
> EPICS_CA_MCAST_TTL=20
>
> caRepeater did not join the beacon IGMP multicast group, so I used a multicast address for the
> beacons which the client node was already listening to.
>
> The control system has a large central router which is connected to about a dozen 256 address subnets.
> Each subnet is only 1 hop from the others. More hops would be needed to get to non-controls subnets
> or the internet.
>
> Jim
>> 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
>
- Replies:
- Re: EPICS_CA_MCAST_TTL equivalent for pvAccess Pierrick M Hanlet via Tech-talk
- References:
- EPICS_CA_MCAST_TTL equivalent for pvAccess Denise Finstrom via Tech-talk
- Re: EPICS_CA_MCAST_TTL equivalent for pvAccess Michael Davidsaver via Tech-talk
- Re: EPICS_CA_MCAST_TTL equivalent for pvAccess James G Smedinghoff via Tech-talk
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