Download the VSXi Datasheet


The VSXi session controller provides critical functions for communications service providers, including security and DDOS protection, network address translation, protocol interworking, and traffic management. In the graphic, two pairs of VSXi session controllers are deployed in a high availability (HA) configuration, serving network-facing and subscriber-facing requirements.

Deployed for network interconnection, the VSXi selects optimal routes for voice communications traffic and assuring effective interworking with outside networks.

The session controller is also deployed to manage subscriber-facing traffic, providing packet-header manipulation and digit mapping for automatic number identification (ANI) and dialed number identification services (DNIS) manipulation.

Key functionality provided by the VSXi includes the following:

  • Network topology protection and asset hiding
  • Preventing distributed denial of service (DDOS) attacks through sophisticated network security mechanisms
  • Advanced management of signaling and media throughput under all load conditions
  • Firewall & network address translation (NAT) traversal, near & far end
  • Local number portability (LNP) dipping & complete control of inbound / outbound RN handling
  • Session-routing based on ANI & DNIS jurisdictional control
  • Manages 90M routes in 1000 different route tables
  • Generate call detail records (CDR) w/ retrieval via RADIUS, FTP, RSync, SCP
  • Performance monitoring w/metrics updated in real-time
  • Protocol interworking for SIP and H.323
  • Media transcoding, including fixed and wireless audio codecs and video codecs

The VSXi is the highest performing session control platform in the market today. A single VSXi node scales to 1200 cps and 25K sessions. VSXi clusters of 16 nodes scale to 19,200 cps and 400,000 sessions – all with greater than 99.999% availability. The carrier-grade VSXi can be positioned at the core or edge of the network to manage VoIP traffic between SIP proxies, SIP UAs, H.323 gateways, IP-PBXs and H.323 gatekeepers.

Sansay’s routing tables and LCR capabilities optimize bandwidth costs in a variety of VoIP peering applications, allowing carriers to interconnect without requiring traditional class 4 TDM switches in the call path. Replacing the relevant Class 4 functions—call routing, CDR generation, security and network privacy—the VSXi also acts as the “billing switch” between carriers at a fraction of the cost. VOIP providers can move the peering function off softswitches and gatekeepers to make networks more secure and reliable, and a wide range of services more profitable.

In access applications, Sansay’s VSXi VoIP session controller works in conjunction with Class 5 switches, feature servers and gateways. The VSXi also enables a broad range of differentiated services while ensuring interoperability and secure firewall/NAT/call admission control. The VSXi also acts as a registrar.

Enforcing the Borders of Quality, Cost

Sansay’s VSXi session controllers protect network topography while preventing denial of service (DoS) attacks to keep service provider infrastructures secure within the internal VPN. Our SBCs support SLAs and eliminate the voice quality degradation and delays caused by multiple compression/decompressions when TDM equipment is used to switch VOIP calls between carriers. Sansay also interconnects to leading ENUM databases to enable providers to minimize costs by completing calls using all-VoIP networks whenever possible.

Architected for profitable growth for both niche applications to the world’s largest service providers, Sansay helps reduce not only the costs of building and managing networks, but of operating services themselves. Performing multiple functions, the VSXi minimizes the cost and complexity associated with maintaining extra gateways, softswitches and port licenses.

Sansay session controllers are the building blocks of networks that perform to expectations, but don’t take our word for it. Our products are utilized by nearly 300 referenceable service providers worldwide many of whom will gladly talk about us. Please contact us to speak to a Sansay customer and learn more.

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Download the MST Datasheet

The Sansay MST is a transcoding subsystem that enables communications service providers to convert the media encoding of audio and video traffic. The MST enables operators to support an increased variety of devices and codecs, reduce carrier termination costs, and enhance security through traffic encryption.

The MST functions as a transcoding resource within Sansay’s VSXi session controller. The VSXi uses H.248 to direct media streams to the MST as a part of normal session control functions and traffic handling.

By deploying the MST as a part of VSXi session control, transcoding is performed with the same active level of session control, reporting, and high availability as standard VSXi media handling.

The VSXi cost-effectively supports a distributed deployment, enabling service providers to extend security functions and optimize session routing. Transcoding as a part of distributed deployment offers two clear benefits for service providers:

  • Eliminates added signaling, CDRs, and session ports required by outboard transcoding
  • Transcodes with minimal network hops and minimizes possible traffic hair-pinning

Transcoding as a part of session control functions results in simplification of network operations as well as optimized session routing which can result in reduced latency and jitter.

MST setup and configuration is performed through added elements in the VSXi GUI. Sessions are targeted for transcoding by trunk ID (TID). Codecs are specified using a drop-down selection.

The MST is a straightforward addition for VSXi operators looking to add transcoding.