Chapter 5. IOS IP Telephony Skills
The Cisco IP telephony product range includes IOS-based devices and mechanisms, including Survivable Remote Site Telephony (SRST), CallManager Express (CME), and Cisco Unity Express (CUE).
Survivable Remote Site Telephony
Survivable Remote Site Telephony (SRST) is a feature which ensures that IP phones can continue to function even if they are unable to communicate with CallManager. During a failure, Cisco IP phones register with the local SRST router, which provides call processing and control. If Cisco IP phones detect that CallManager has come back online, they can fail back to that CallManager after a configurable interval (connection monitor duration). Cisco IP phones do not fail back immediately to ensure ...