Samsung Ubigate iBG3026 Configuration Manual page 365

PSTN Fallback
Ubigate iBG3026 monitors status of the IP network(WAN). When WAN fail is
detected, Ubigate iBG3026 system redirects calls to the PSTN automatically.
When the WAN link is restored, call routing reverts back to the IP Network.
This feature is called PSTN Fallback and enables an end-user to give a
reasonable guarantee about call completion.
Survivable Telephony
Ubigate iBG3026 provides survivable telephony functionality which is very
important for the remote site branch office which is connected over the WAN
link.
When the link which is only link to IP network was failed, there is no way to
communicate with Call Manager at the central sites. It is impossible to VoIP
call setup through Call Manager. Even in this case, Ubigate iBG3026 has
ability to provide the voice call services to local subscriber not only analog
phones but also IP Phones.
In Call Manager Interworking mode, Ubigate iBG3026 systems act as a
stateless proxy server, which sends and receives SIP message between IP
phone and Call Manager transparently. When IP Phone register to Call
Manager, Ubigate iBG3026 system finds the information about IP phone
location and subscriber profile. Ubigate iBG3026 system always checks WAN
connection status between Call Manager and Ubigate iBG3026.
If Ubigate iBG3026 detects connection fail, it changes to Survivable
Telephony mode automatically.
In Survivable Telephony mode, Ubigate iBG3026 acts as a SIP server for local
call. Using IP phone location and subscriber profile information, Ubigate
iBG3026 provides basic call and restricted supplementary service.
Active calls between users on the same LAN are not affected by WAN failure
and will last for the duration of the call. Survivable Telephony provides below
services:
Local extension dialing IP Phone to IP Phone calls
IP Phone to PSTN calls
IP Phone to analog device calls
It is recommended that all Ubigate iBG3026 in remote offices maintain direct
links to the PSTN for backup callout capability. This is particularly important
for maintaining emergency calling capability.
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