RE: Channel access over wireless?

["Hill, Jeff" <johill@lanl.gov>]

The 3.14 CA search and connect algorithms are actually much better about dealing with congestion compared to circa R3.12 and R3.13. In particular, the search request intervals dynamically respond to congestion. Also, the applications disconnect, but tcp circuits don’t disconnect, if there are brief interruptions in service.

 

Jeff

 

From: tech-talk-bounces@aps.anl.gov [mailto:tech-talk-bounces@aps.anl.gov] On Behalf Of Ralph Lange
Sent: Thursday, October 31, 2013 12:14 PM
To: EPICS Tech-Talk
Subject: Re: Channel access over wireless?

 

On 31.10.2013 18:55, Emmanuel Mayssat wrote:

I am contemplating a project which requires wireless communication.
I would like to have telemetry information on a control station.
The network link specification is: range 1 mile at 250Kbps
Latency could definitely be an issue (measurement needed at this point)
I could potentially have several 250Kpbs links (not sure whether they can be 'trunked' together)

The remote device could run an IOC (I need something like a 'fast' sequencer for sure)
Between local OPI and remote IOC, I can use any communication protocol I want

Classic architecture:
local OPI ---- (CA over wireless) --- remote IOC
is there a way for an OPI to bypass the UDP discovery process and force connection to a specific IP addres/port?

Setting EPICS_CA_AUTO_ADDRESS=NO suppresses the UDP broadcast
Setting EPICS_CA_ADDRESS_LIST restricts discovery traffic to a list of IP/port addresses
Setting EPICS_CA_NAME_SERVERS uses TCP for discovery traffic to a list of IP/port addresses

Setting both
   EPICS_CA_AUTO_ADDRESS=NO
   EPICS_CA_NAME_SERVERS=your.destination.ip.address:port
will run Channel Access exclusively to that server/port, using TCP for name resolution and data.
You could e.g. use this to tunnel CA through SSH.

You can find more information in the Channel Access Reference Manual.

HTH,
~Ralph