How to Choose an SBC for Your Voice Operation

What a Session Border Controller Does

An SBC (Session Border Controller) acts as the control point between distinct network domains. In practice, it sits at the border between your internal network and the public network, or between your network and another operator's. Its primary functions include:

• Border security: protection against SIP attacks (scanning, brute-force, INVITE and REGISTER flooding), request rate limiting, and malicious traffic filtering.
• NAT traversal: manipulation of SIP headers and SDP to ensure media (RTP) flows correctly when devices are behind NAT.
• Protocol normalization: translation between SIP variants, adjustment of proprietary headers, and interoperability between equipment from different vendors.
• Topology hiding: concealing internal network topology, preventing the external side from discovering internal IP addresses, ports, and server structure.
• Encryption: TLS termination and origination (signaling) and SRTP (media), allowing traffic between the border and the outside world to be encrypted even when SIP/RTP without encryption is used internally.

SipPulse SBC: Three Variants for Every Scenario

The SipPulse SBC was designed to serve different voice operation scenarios, with three variants that cover everything from subscriber access to carrier interconnection and contact center operations.

SipPulse SBC UNI (User-to-Network Interface)

The SBC UNI is the variant built for the access edge. It sits between subscriber endpoints (IP phones, ATAs, PBXs) and the network core. Its main functions include:

• Protecting the softswitch from attacks originating on the internet
• NAT traversal for subscribers behind residential or enterprise routers
• SIP signaling normalization from equipment made by different vendors
• TLS and SRTP support for end-to-end encryption
• WebRTC support, enabling browser-based softphones to connect directly to the core

The SBC UNI is the right choice for ISPs offering voice services that need a robust border between their subscribers and the switching infrastructure.

SipPulse SBC NNI (Network-to-Network Interface)

The SBC NNI is built for the interconnection edge between carriers. It operates at the peering point between your network and other operators' networks, ensuring:

• Complete topology hiding, preventing the partner carrier from seeing your internal network structure
• Protocol normalization for compatibility between softswitches from different vendors
• Routing policy enforcement and traffic control per interconnection
• Native STIR/SHAKEN support for call origin verification
• Capacity of up to 4,000 concurrent calls per channel

The SBC NNI is essential for STFC operators that maintain multiple interconnection agreements and need granular control over each peering's traffic.

SipPulse SBC NNI-CC (Contact Center)

The SBC NNI-CC is a specialized variant for contact center operations. In addition to all NNI functions, it adds:

• Native integration with predictive dialing and IVR platforms
• CPS (calls per second) control per campaign, preventing network overload
• Oleg integration with unified communications platforms like Zoom and Microsoft Teams
• WebRTC support for browser-based agents, eliminating the need for dedicated softphones
• Integration with SipPulse CPA (Call Progress Analysis) for 99.9% accurate call progress detection, identifying voicemail before answer via Early Media ML

SipPulse SBC Capacity

The SipPulse SBC supports up to 4,000 concurrent calls per channel, with the ability to scale horizontally by adding channels as demand grows. The architecture is built on OpenSIPS, which ensures high performance in SIP signaling processing.

For operations requiring media transcoding, the SipPulse SBC integrates with RTPEngine, enabling transparent conversion between codecs (G.711, G.729, Opus) with no perceptible impact on latency.

Comparison with Other Market SBCs

AudioCodes Mediant

The AudioCodes Mediant line is widely used in PSTN operations and contact centers. It offers hardware and virtual versions with an intuitive management interface. However, the cost per concurrent session tends to be significantly higher than software-based solutions, and integration with third-party softswitch ecosystems may require customization.

Oracle (Acme Packet)

The Oracle SBC is the reference for large Tier-1 carriers, with high CPS capacity and centralized management via Oracle Communications Session Delivery Manager. It is a robust solution, but with high licensing costs and deployment complexity that can be disproportionate for ISPs and mid-size carriers.

Ribbon (formerly GENBAND/Sonus)

High-capacity SBCs targeted at Tier-1 carriers, with support for virtualization and cloud-native deployments. Like Oracle, cost and complexity are limiting factors for smaller operations.

Why SipPulse SBC Stands Out

The SipPulse SBC offers specific advantages for ISPs, contact centers, and telecom operators in Brazil and Latin America:

1. Cost-effectiveness: built on OpenSIPS, it eliminates per-session licensing costs that make proprietary solutions expensive.
2. Integrated ecosystem: works natively with SipPulse SoftSwitch, SipPulse BSS, and SipPulse CPA, eliminating the need for complex integrations between different vendors.
3. Native STIR/SHAKEN: integrated support for the call origin verification framework, preparing your operation for Anatel's Origem Verificada requirements.
4. Three specialized variants: instead of a generic product, the SipPulse SBC offers variants optimized for each scenario (access, interconnection, contact center).
5. WebRTC and modern integrations: Oleg integration with Zoom and Microsoft Teams, plus native WebRTC support for modern contact center operations.
6. Local support: a technical team specialized in Brazil's regulatory environment, with deep knowledge of Anatel's STFC requirements.

Placement in Network Topology

With the three SipPulse SBC variants, network topology becomes clear and organized:

1. SBC UNI at the access edge: between subscribers and the SipPulse SoftSwitch. Protects the core from internet-originated attacks and normalizes traffic from heterogeneous endpoints.
2. SBC NNI at the interconnection edge: between your network and other carriers' networks. Ensures topology hiding, protocol normalization, and interconnection policy enforcement.
3. SBC NNI-CC for contact centers: between the dialing/answering operation and the voice network. Manages CPS, integrates with UC platforms, and enables WebRTC for agents.

This separation allows you to size each network point independently, scaling the access edge as subscriber count grows and the interconnection edge as new peerings are added.

Sizing in Practice

To size the SipPulse SBC for your operation, gather the following data:

• Peak concurrent sessions (measure over 30 days on your SipPulse SoftSwitch)
• Peak CPS (observe business hours, especially between 10am and noon)
• Percentage of calls requiring transcoding
• Number of interconnection points with other carriers
• WebRTC traffic volume (if applicable)

With this data, the SipPulse technical team will size the ideal configuration, defining how many SBC channels are needed and which variant should be used at each network point. See the full SipPulse SBC datasheet for detailed capacity specifications.

References

• RFC 3261 - SIP: Session Initiation Protocol: https://datatracker.ietf.org/doc/html/rfc3261
• OpenSIPS: https://opensips.org/
• RTPEngine: https://github.com/sipwise/rtpengine
• SipPulse SBC Datasheet: /datasheets/sbc-v4.pdf
• SipPulse SoftSwitch Datasheet: /datasheets/softswitch-v3.pdf