Cisco
Unified SIP SRST provides backup to an external SIP proxy server by
providing basic registrar and redirect server or back-to-back user agent
(B2BUA) services. These services are used by a SIP IP phone in the
event of a WAN connection outage when the SIP phone is unable to
communicate with its primary SIP proxy.
Cisco
Unified SIP SRST can support SIP phones with standard RFC 3261 feature
support locally and across SIP WAN networks. With Cisco Unified SIP
SRST, SIP phones can place calls across SIP networks in the same way as
SCCP phones.
Cisco Unified SIP SRST supports the following call combinations:
- SIP phone to SIP phone
- SIP phone to PSTN / router voice-port
- SIP phone to Skinny Client Control Protocol (SCCP) phone
- SIP phone to WAN VoIP using SIP
