Session Border Controller (SBC)

What is Session Border Controller (SBC)?

SBC is a security device that controls and protects VoIP (Voice over Internet Protocol) communications at network boundaries. It’s positioned between corporate and external networks and acts like a checkpoint, inspecting all calls and video communications before allowing them through.

In a nutshell: It’s a “customs” for phone communications, allowing only safe calls through.

Key points:

• What it does: Inspects VoIP communications, enforces security policies, and manages communication quality
• Why it’s needed: Protects against fraudulent calls, fraud, security threats, and guarantees communication quality
• Who uses it: Enterprises, contact centers, communication service providers

Why it matters

VoIP communications use the internet, so security risks are high. Threats include fraudulent calls from unauthorized callers, eavesdropping on communications, and unauthorized call charge usage.

SBC detects and blocks these threats, allowing only authorized communications through. Additionally, it monitors communication quality and manages bandwidth, prioritizing important calls.

How it works

SBC functions through three layers.

Signaling layer: Inspects SIP protocol and determines if call requests are legitimate. Verifies authentication credentials and checks for policy violations.

Media layer: Monitors whether actual audio data is correctly routed and performs encryption or quality adjustments as needed.

Security layer: Implements firewall functions, intrusion detection, and denial-of-service attack protection.

Execution flow: Call request arrives → SBC inspects → verifies policy → sets encryption → forwards to destination → continues monitoring call quality

Real-world use cases

Enterprise VoIP deployment Protects calls between internal users and external partners via SBC, preventing unauthorized access.

Cloud PBX integration Safely connects on-premises traditional phone systems with cloud-based VoIP services.

Multi-site enterprise unified communications Centralizes calls between multiple branch offices through SBC and guarantees high-quality communications.

Benefits and considerations

Benefits: Enhanced security, improved communication quality, centralized operations, and regulatory compliance.

Considerations: Configuration is complex and requires specialist knowledge to manage. Additionally, vendor lock-in risks and high initial investment are challenges.

Related terms

• VoIP — communication technology that SBC protects
• SIP Protocol — communication protocol that SBC monitors
• Firewall — basic function of SBC
• Network Security — purpose of SBC
• Cloud PBX — system that works with SBC

Frequently asked questions

Q: Can it be retrofitted to existing phone systems? A: Yes. Many SBCs have interoperability with legacy systems.

Q: Is it necessary for all VoIP systems? A: It depends on security requirements. It may not be necessary for internal-only systems, but it’s strongly recommended for external connections.