SAS (Standalone Survivability) - Definition
Customers who connect to centralized IP-Centrex services, as well as branch offices of Enterprises that use a centralized IP-PBX server may face a survivability challenge. These remote locations may lose all voice services (including internal calls and PSTN breakout) due to the connectivity loss between the remote site and the central IP Centrex application server or IP-PBX. This issue challenges service providers who offer IP-Centrex services and enterprises that deploy a distributed IP-PBX solution.
SAS (Stand Alone Survivability) is a feature based on SIP B2BUA (Back to Back User Agent) functionality, targeting customers of SIP IP-Centrex services and Enterprise branch offices. SAS enables the service backup for SIP clients such as SIP IP Phones and SIP Soft Phones in the case of a network failure. This backup is performed by the Media Gateway installed as a CPE in the customer premises or branch office.
Once the SAS feature has been configured on the Media Gateway, the SIP clients register with their central SIP Proxy (the IP Centrex server or the enterprise central IP-PBX) via the Media Gateway that acts as a proxy for all SIP registrations. In the case of connectivity loss with the centralized IP Centrex application or IP-PBX platform, the Media Gateway takes control, enabling new phone registrations and internal calls in the disconnected site. PSTN connectivity will also be backed up if there is a local PSTN connection in the gateway. During network downtime, basic call control features are provided by the Media Gateway, and full functionality is restored once the network has recovered.
SAS (Standalone Survivability) - Synonyms
SAS, Standalone Survivability; Back-to-Back user agent; B2BUA; B2BUA SIP; B2BUA Software