Industry trends are pushing the transition to SIP telephony deeper into the network, including to the vital links between the switching core and the access network that delivers local service to subscribers.
Meanwhile, the regulatory requirement for Emergency Standalone service remains. Protecting that SIP traffic from the impact of losing connectivity to the core network is a key part of ensuring continuous voice service and particularly emergency calling.
Metaswitch ESA Proxy protects a remote site in any network architecture in which the link between the remote site and the core is SIP.
Acting as their primary SIP registrar, the Metaswitch ESA Proxy monitors the core network’s registrations of SIP phones, BLCs and other network endpoints, and builds a database of these connections.
If the link to the core network goes down or the central switch becomes unresponsive, even temporarily, ESA Proxy swings into action using the learned registration information to maintain local calling functionality. ESA Proxy can also use a fall-back trunk to attempt to complete non-local calls.
Once the central switch is back online, the ESA Proxy reverts to its normal mode of monitoring registrations, and call handling is once again handled by the central switch.
The ability to reach emergency first responders is the critical feature of ESA requirements in most jurisdictions. ESA Proxy supports this using a trunk to the Public Safety Answering Point (PSAP) or diversion to a local emergency number (e.g. the police station).
Internally fault-tolerant, ESA Proxy can be deployed on dedicated virtual machines using VMware and OpenStack/KVM, or on ATCA hardware, either on its own or collocated with related Metaswitch products.