Emergency Standalone Proxy

Service survivability for today’s SIP-centric voice infrastructures


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      • Meet regulatory requirements for service survivability

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      • Complete support for any modern access technology

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      • Highly scalable: up to 500,000 subscribers per instance

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      • Flexible collocation and standalone deployment options

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      • Integrated with MetaView network management system


The transition from fixed-line TDM telephony services to Voice over IP (VoIP) is progressively pushing VoIP’s signaling mechanism - the Session Initiation Protocol (SIP) - even further towards the network edge, encompassing not only trunking and interconnect but also the critical connections between the switching core and the access infrastructure responsible for delivering local subscriber services.

This architectural trend is driven by a number of factors.

  • SIP-based customer premises equipment (CPE), in the form of soft-clients, ATAs and VoIP handsets, is becoming prevalent in the home and the enterprise.
  • As the IP Multimedia Subsystem (IMS) takes hold in wireline networks, traditional TDM-based access devices such as Digital Loop Carriers (DLCs) and their associated northbound media gateways are now controlled by Access Gateway Control Functions (AGCFs), with trunk connections to the core using SIP.
  • SIP-based Broadband Loop Carriers (BLCs) and Multi-Service Access Nodes (MSANs) are increasingly the technology of choice for fixed-line telephony, whether over traditional copper lines delivering POTS + DSL, or over fiber as part of an HFC or FTTx deployment strategy.

While this new reality asserts itself, the old reality of the regulatory requirement for Emergency Standalone, to support critical lifeline and first responder services, remains. Protecting SIP traffic from the impact of lost connectivity to the central core is a key part of ensuring continuity of voice services and in particular access to emergency calling. 

Product description

Product description

Metaswitch’s Emergency Standalone (ESA) Proxy preserves voice calling capability and emergency service access in heterogeneous access networks connected to a SIP core.

Adding ESA functionality into an operator’s network architecture is easy. The ESA function acts as a SIP proxy Registrar, monitoring registrations and building a dynamic database of endpoints, while passing the registrations into the core network Registrar as usual. From mobile clients to BLCs, registered endpoints can include any device that presents an upstream SIP interface to the core network. If the access network loses connectivity with the core network, the ESA Proxy uses its learned registration information to maintain service continuity and call capabilities within its service area.

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