If you are using the ATA with callmanager I would suggest if using SCCP. If you are not using with callmanager I am not sure what to recommend since I don't know what you are using the gateway for. SCCP is better for callmanager because the ccm can control the ATA and there is less administration at the ATA.
It really depends on what you are connecting the ATA to. Some device on do h.323 so you would use the ATA in h.323. If the device on uses SIP then use the ATA with SIP. If the device more than one then use the one that works the best. How are you going to use the ATA?
SCCP gives you enhanced features ie transfer , call fwd no reply,busy,all. along with programmed in call manager devices-phone.
If used as and H323 gateway more administration on the ATA and in call manager ( H323 gateway and route patterns) but you have the ability due to the dial plan being built into the ATA that if the call manager fails it can still make calls to the gateway by having a second gateway entry in the ATA (ie first entry points to the call manager)
My understanding with the ATA using SIP it will need to talk to a SIP proxy server not call manager as SIP is not supported on call manager , maybe someone can clarify this point.
I'm not able to access my old voice mail messages all of a sudden. The recording says something like 'the message is currently not available'. This has never happened before in all the years I have been using this system. I have t...