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SIP Trunking - Market Requirements

As Service Providers and Enterprises move towards all-IP services, they face additional challenges interoperating between different VoIP systems. As a result new requirements have recently been introduced to the market, including Operator-to-Business SIP Trunking, Business-to-Business connectivity and Business Inter-Branch connectivity. All these require IP to IP mediation, SIP translation and enhanced VoIP security, performed by enterprise-class Session Border Controllers (SBC).

An SBC is a B2BUA device (Back to Back User Agent), that acts as a server for the internal network, and as a client for external networks handling all aspects of a VoIP call, including: session set-up, session disconnection and the creation of a complete separation between networks. This capability also allows for the addition of features such as billing, network topology hiding, call admission control, authorization, and many more.

SIP Trunking - AudioCodes Solution

IP to IP mediation introduced in version 5.4 for the Mediant 1000 is the first of numerous SBC capabilities, which are fully featured in the Mediant 1000 MSBR (Multi-Service Business Router). New features that are introduced as part of version 5.4 are:

• SIP to SIP normalization - Allows two SIP systems to interconnect by means ofnormalizing different SIP implementations. The “Normalizer” acts as a server on one side, terminating incoming sessions of one SIP implementation, and as a client on the other side initiating new sessions of a different SIP implementation.
  
• Network topology hiding - By acting as a B2BUA device, external users have no visibility of the internal network topology (i.e. endpoints, signaling and traffic), thus providing an important degree of security. In addition, a further security level is achieved by encryption of SIP header fields existing on the network.
  
• Media transcoding and conversion - The gateway can translate voice traffic between two separate networks which use different coders or media payloads. An example is the transcoding between WAN and LAN on the edge of the Enterprise network (in the case of a SIP trunk being provided) or when peering between two Enterprise networks.
  
• Signaling Translation - Converting between SIP <> SIP-TLS over TCP or UDP (any to any).
  
• Multiple Service Provider connectivity - An Enterprise can use multiple SIP trunks provided by several service providers, allowing dynamic provider selection for least cost routing and service redundancy.
• Load balancing and redundancy between Servers/Softswitches - The Media Gateway allows concurrent connectivity to two servers (belonging to the same service provider) as well as enabling fallback and load-balancing between them.
  
• Survivability - As a B2BUA device, the gateway provides Stand Alone Survivability and maintains internal connectivity when the central Softswitch is unavailable. This is a different method of survivability compared to the previous one as presented by the SAS feature, in which the gateway acts as a proxy (usually used in IP-Centrex environments).

SIP Trunking Features

• Rich interoperability enabling compliance with a wide variety of Softswitches for the SIP Trunking Service
• Rich interoperability enabling compliance with a broad range of IP-PBX vendors on the Enterprise side
• Concurrent PSTN connection for Lifeline fallback and least cost routing
• Microsoft Certified Gateways providing an interoperability solution in many new Microsoft Office Communications Server (OCS) deployments