Best Session Border Controllers (SBC)

Guide to Session Border Controllers

Session Border Controllers (SBCs) are specialized network devices used in Voice over IP (VoIP) communications to manage and secure the signaling and media streams involved in setting up, conducting, and tearing down voice or video calls. Positioned at the borders between different networks—such as between an enterprise and a service provider—they perform critical functions like protocol interworking, network topology hiding, and call admission control. SBCs help ensure that voice and video traffic can traverse different network environments seamlessly, even when these networks use varying protocols or configurations.

Security is one of the primary functions of an SBC. These controllers act as gatekeepers, protecting against threats such as denial-of-service (DoS) attacks, toll fraud, and eavesdropping. By inspecting and filtering signaling and media packets, SBCs can enforce policies that block malicious traffic and enforce compliance with regulatory or organizational requirements. They can also encrypt VoIP traffic using protocols like Secure Real-Time Transport Protocol (SRTP) and Transport Layer Security (TLS), ensuring the privacy and integrity of communications.

Beyond security and interoperability, SBCs offer tools for quality of service (QoS) management, enabling network operators to prioritize voice traffic and monitor performance in real time. They can detect and correct issues such as jitter, packet loss, and latency, which are critical to maintaining high call quality. In enterprise environments, SBCs support flexible routing policies and facilitate migration to cloud-based or hybrid communications platforms. As organizations increasingly adopt unified communications and SIP trunking, SBCs play an essential role in ensuring reliable and secure connectivity between users, devices, and services.

Features of Session Border Controllers

• Security and Network Protection: SBCs provide topology hiding, firewalling, and DoS/DDoS protection to shield the internal VoIP network from malicious attacks. They also support encryption (TLS, SRTP) and user authentication to ensure secure signaling and media transmission.
• Protocol and Codec Interoperability: SBCs normalize SIP messages, convert codecs (e.g., G.711 to G.729), interwork between protocols like SIP and H.323, and handle DTMF translation. This allows devices and networks from different vendors to communicate seamlessly.
• Quality of Service (QoS) Management: With features like call admission control (CAC), jitter/latency monitoring, and traffic prioritization using DSCP markings, SBCs maintain high call quality by managing bandwidth and prioritizing voice traffic.
• Dynamic Routing and Policy Control: SBCs offer flexible call routing based on cost, time, or availability, and enforce dial plans and number manipulation rules. They also perform load balancing and session steering to distribute traffic efficiently across network elements.
• Monitoring, Compliance, and Analytics: SBCs support lawful intercept, generate detailed call detail records (CDRs), and provide real-time quality analytics and alerts. These tools are vital for regulatory compliance, billing, and troubleshooting.
• High Availability and Scalability: Designed for carrier-grade performance, SBCs support high availability (HA), failover, and horizontal scaling to ensure continuous service even under heavy loads or hardware failures.
• Media Control and NAT Traversal: SBCs anchor or relay media for better control and security, and enable NAT traversal so VoIP traffic can pass through routers and firewalls without issues, especially for remote endpoints.
• Testing and Simulation Tools: Some SBCs include built-in load testing and simulation capabilities to help administrators validate performance and detect configuration issues before going live.

What Are the Different Types of Session Border Controllers?

• By Deployment Type: Session Border Controllers can be deployed in various environments. Enterprise SBCs are used within businesses to secure internal networks and manage SIP trunking. Carrier or service provider SBCs are designed for telecom companies to handle large-scale traffic and interconnection. Cloud-based SBCs offer flexibility and scalability for modern VoIP systems by operating entirely in virtualized or hosted environments.
• By Functionality: Depending on their focus, SBCs may specialize in different functions. Signaling SBCs handle SIP messages and ensure compatibility and security across different systems. Media SBCs control voice and video streams, providing transcoding and encryption. Hybrid SBCs manage both signaling and media in one solution, offering comprehensive control.
• By Architecture: SBCs come in different architectural forms. Hardware-based SBCs are physical devices with dedicated processing capabilities for high performance. Software-based SBCs run on general-purpose servers, providing flexibility and cost efficiency. Virtual SBCs are designed for cloud or virtualized environments, offering automation and scalability through containers or VMs.
• By Network Location: The role of an SBC varies by where it sits in the network. Access SBCs are deployed between enterprises and service providers to protect the edge and manage session admission. Interconnect SBCs are placed between service providers to normalize protocols and enforce peering policies. Edge SBCs reside at the network perimeter, protecting against external threats and ensuring session continuity.
• By Use Case Specialization: Some SBCs are tailored for specific environments. Mobile SBCs are optimized for mobile networks like VoLTE and support unique signaling like Diameter. Hosted SBCs are managed by third-party providers, ideal for businesses that prefer not to maintain SBCs themselves.

Session Border Controllers Benefits

• Protection Against Malicious Attacks: SBCs defend against various cyber threats such as Distributed Denial-of-Service (DDoS) attacks, call hijacking, toll fraud, and eavesdropping. They inspect and filter signaling and media packets, effectively identifying and blocking unauthorized traffic.
• Topology Hiding: By masking internal network IP addresses and architecture, SBCs prevent external users or attackers from gaining insight into the private structure of the communication network, reducing the risk of targeted attacks.
• Encryption Enforcement: SBCs enable secure transmission of signaling and media using protocols like Secure Real-time Transport Protocol (SRTP) and Transport Layer Security (TLS), ensuring that communications remain private and tamper-proof.
• Protocol Translation: In environments with multiple vendors and differing protocol implementations, SBCs act as translators between different signaling protocols (e.g., SIP, H.323), codecs, or header formats, enabling seamless communication across diverse systems.
• Codec Negotiation: SBCs mediate codec mismatches by transcoding audio streams to compatible formats, ensuring smooth voice and video communication between endpoints with differing capabilities.
• Network Normalization: They adapt messages to conform to the expected formats and behaviors of downstream equipment, improving compatibility and reducing integration issues.
• Traffic Prioritization: SBCs support QoS mechanisms like Differentiated Services (DiffServ) to prioritize voice and video traffic over less sensitive data, improving the overall user experience.
• Jitter and Packet Loss Mitigation: By optimizing Real-Time Transport Protocol (RTP) streams, SBCs help smooth out jitter, minimize packet loss, and manage latency to deliver clearer, uninterrupted communication.
• Media Anchoring: They can anchor media streams to central points, allowing better control over call routing, troubleshooting, and call recording functionalities.
• Call Logging and Lawful Interception: SBCs facilitate compliance with legal requirements by enabling call detail record (CDR) generation and lawful interception capabilities as mandated by government regulations.
• Emergency Services Support: Some SBCs provide features to assist with emergency call routing and location identification, aligning with E911 or similar regulations in various jurisdictions.
• Dynamic Call Routing: SBCs route calls based on policies such as least cost routing, time-of-day, geographic origin, and load balancing, optimizing the efficiency and cost-effectiveness of communication.
• Session Admission Control: They prevent network congestion by monitoring and limiting the number of concurrent sessions based on available bandwidth and system resources.
• Policy Enforcement: SBCs enforce enterprise communication policies, such as call restrictions or access control rules, ensuring compliance with organizational guidelines.
• Separation of Domains: SBCs create a clear demarcation between internal and external networks (e.g., enterprise vs. carrier networks), which is essential for multi-tenant environments and secure service delivery.
• NAT Traversal: SBCs facilitate Network Address Translation (NAT) and firewall traversal, allowing SIP and RTP traffic to flow seamlessly across boundaries that would otherwise block such traffic.
• Failover and Redundancy: Many SBCs support high-availability configurations with features like active/standby failover and session mirroring to ensure uninterrupted service during hardware or network failures.
• Load Balancing: SBCs distribute traffic loads across multiple gateways or servers, improving system reliability and performance under varying traffic conditions.
• Bandwidth Efficiency: By compressing media streams and avoiding unnecessary transcoding, SBCs help reduce the bandwidth required for VoIP traffic, lowering operational costs.
• Peering and Trunk Optimization: SBCs facilitate the efficient use of SIP trunks and peering connections by managing session limits and balancing loads, helping organizations reduce telecommunication expenses.
• Real-time Monitoring: SBCs provide dashboards and tools for real-time monitoring of call quality, session statistics, and network health, enabling quick detection and resolution of issues.
• Troubleshooting Support: With detailed logging and session trace capabilities, SBCs help network administrators diagnose and resolve call failures or quality issues more effectively.
• Reporting and Analytics: SBCs generate detailed usage reports and analytics that inform capacity planning, SLA adherence, and service improvement initiatives.
• Cloud Integration: Modern SBCs are cloud-native or cloud-compatible, making them ideal for organizations using cloud-based VoIP or UCaaS platforms.
• Hybrid Deployments: SBCs enable seamless interworking between on-premises systems and cloud services, supporting flexible migration strategies and coexistence scenarios.

Who Uses Session Border Controllers?

• Telecommunications Service Providers (TSPs) / Carriers: SBCs play a critical role in protecting their VoIP networks from security threats, managing Quality of Service (QoS), handling media transcoding, and ensuring regulatory compliance (e.g., lawful intercept). SBCs also help in interconnecting different signaling protocols and managing peering relationships with other carriers.
• Enterprises / Large Corporations: Enterprises use SBCs to secure their unified communications platforms (such as Microsoft Teams, Cisco Webex, or Zoom Phone), ensure interoperability between various telephony systems, manage remote access for workers, and implement call routing policies. They also help in enforcing communication policies and facilitating secure SIP trunking with service providers.
• Contact Centers / Call Centers: Contact centers rely on SBCs to maintain call quality, scale traffic during peak periods, provide NAT traversal for remote agents, ensure call recordings and compliance, and secure communications against threats such as toll fraud, eavesdropping, and Denial-of-Service (DoS) attacks.
• Unified Communications as a Service (UCaaS) Providers: UCaaS providers deploy SBCs to enable secure and seamless SIP trunking, protect their infrastructure from malicious attacks, provide interworking between customer PBX systems and their cloud platforms, and manage call admission control (CAC) to preserve service quality.
• Managed Service Providers (MSPs) / System Integrators: These providers integrate SBCs into their customers’ voice and data networks to ensure security, optimize performance, and provide managed services such as analytics, reporting, and compliance auditing. SBCs also support seamless migrations to VoIP or hybrid cloud environments.
• Internet Telephony Service Providers (ITSPs) / VoIP Providers: ITSPs need SBCs to handle SIP signaling, manage interoperability between different VoIP platforms, enforce call admission and routing policies, and provide NAT traversal and secure media paths. They also rely on SBCs for real-time monitoring and fraud prevention.
• Government Agencies / Public Sector Organizations: Security is paramount for public sector entities. SBCs provide encryption, identity verification, and denial-of-service prevention, while also helping integrate legacy systems with modern VoIP infrastructures. They enable lawful intercept and meet stringent compliance standards like FIPS or NIST.
• Healthcare Institutions: To ensure compliance with HIPAA, maintain secure and reliable communications, and support remote consultations. SBCs offer encryption and access controls, along with interoperability between various healthcare communication platforms.
• Educational Institutions: Educational organizations use SBCs to support secure VoIP and video conferencing, connect remote campuses or students, and provide interoperability with commercial telephony systems. SBCs also help manage bandwidth and enforce usage policies.
• Hospitality Industry (Hotels, Resorts, Casinos): SBCs help manage VoIP services for guests, enable secure call handling for reservations and customer service, and provide integration between legacy PBX systems and modern VoIP platforms. They also ensure service availability and protect against fraudulent activity.
• Retail Chains and Franchises: Retailers use SBCs to unify their communication systems across locations, protect sensitive data such as payment details, and ensure secure, high-quality communication between stores, warehouses, and headquarters.

How Much Do Session Border Controllers Cost?

The cost of session border controllers can vary significantly depending on several factors, including the deployment model (hardware-based vs. software-based), the number of concurrent sessions required, and the feature set needed for security, interoperability, and traffic management. For small to mid-sized businesses, software-based SBCs might range from a few hundred to several thousand dollars, offering flexibility and scalability without the need for dedicated hardware. Larger enterprises or service providers requiring high throughput and advanced features like transcoding, deep packet inspection, and robust policy enforcement might invest tens of thousands of dollars in high-performance SBC solutions.

In addition to the initial purchase price, organizations must consider ongoing costs such as licensing fees, support contracts, and software updates. Some SBC providers offer subscription-based pricing models, which can affect total cost of ownership over time. Deployment in cloud environments might also involve additional expenses related to cloud infrastructure usage. Ultimately, the total investment in SBCs should align with an organization’s communication needs, compliance requirements, and long-term scalability goals. Careful planning and assessment of expected call volume and desired functionality are essential to ensure cost efficiency and optimal performance.

Session Border Controllers Integrations

Session Border Controllers can integrate with a range of software systems that support or enhance real-time communication, particularly those involving Voice over IP (VoIP) and Unified Communications (UC). One primary category includes VoIP softswitches and IP-PBX systems, which use SBCs to secure and manage voice traffic across network borders. These integrations help ensure reliable call routing, NAT traversal, and protocol normalization while providing security features such as encryption and protection against DoS attacks.

Another key integration is with Unified Communications platforms, such as Microsoft Teams or Zoom Phone. These platforms rely on SBCs to enable direct routing of voice traffic between the public switched telephone network (PSTN) and cloud-based communication environments. The SBC acts as a secure and controlled gateway, enforcing policies, transcoding media, and providing failover capabilities.

Call center and contact center software also often integrates with SBCs to manage high volumes of SIP-based calls securely and efficiently. These integrations support recording, call analytics, quality monitoring, and traffic shaping, which are crucial for maintaining service quality and compliance.

Additionally, SBCs can integrate with network monitoring and management systems to provide real-time insight into call quality, traffic patterns, and potential issues. These tools allow administrators to optimize performance and troubleshoot problems more quickly.

SBCs may integrate with security platforms and policy enforcement engines. This ensures that voice traffic adheres to enterprise security policies, and can include features such as intrusion detection, encryption enforcement, and user authentication. This type of integration is especially important in regulated industries or environments requiring strict data protection and auditability.

Recent Trends Related to Session Border Controllers

• Rising VoIP and SIP Trunking Adoption: The continued shift from traditional PSTN to IP-based communication (VoIP) is a major driver for SBC adoption. Enterprises and service providers need SBCs to ensure security, interoperability, and quality of service.
• 5G Rollout and Network Modernization: As carriers invest in 5G infrastructure, SBCs are being updated and integrated into cloud-native and virtualized environments to support ultra-low latency and high-throughput requirements.
• Explosion of Unified Communications (UC): Platforms like Microsoft Teams, Zoom, and Cisco Webex have fueled demand for SBCs to ensure secure and reliable SIP trunking for voice communication.
• Increased Remote Work: Post-pandemic hybrid and remote work models have elevated the need for SBCs to support secure and scalable remote access to voice networks.
• Growing Cybersecurity Threats: SBCs play a critical role in mitigating SIP-based attacks (e.g., toll fraud, DDoS, spoofing). Vendors are enhancing SBCs with more advanced threat detection and mitigation capabilities.
• TLS and SRTP Encryption: There's a strong industry push toward encrypting SIP signaling and RTP media streams to protect call confidentiality and integrity.
• Zero Trust Architecture Integration: Enterprises are aligning SBC security policies with zero trust principles, ensuring continuous verification and strict access controls for voice communications.
• Shift to Virtualized and Cloud-Native SBCs: Software-based SBCs are replacing legacy hardware appliances. These virtual SBCs run on NFV/SDN infrastructure or public clouds (AWS, Azure, GCP).
• SBC-as-a-Service (SBCaaS): Hosted SBC offerings are becoming popular among enterprises that prefer OPEX models over CAPEX, allowing them to scale quickly without hardware investments.
• Containerization and Kubernetes: SBC vendors are optimizing solutions for containerized deployment environments to enable microservice-based architectures and improved agility.
• Interoperability Challenges: Enterprises with heterogeneous communication environments require SBCs that can ensure compatibility across different vendors’ systems (e.g., Avaya, Cisco, Microsoft).
• Role in Direct Routing for Microsoft Teams: SBCs are critical for connecting SIP trunks to Teams environments, which has become a major selling point for enterprise SBC solutions.
• Codec and Protocol Normalization: SBCs continue to be vital in resolving codec mismatches, header manipulations, and protocol translations between SIP variants.
• Real-Time Monitoring and Troubleshooting: Advanced analytics features are increasingly embedded in SBCs to help network admins identify and resolve call quality or security issues rapidly.
• AI-Powered Insights: Emerging SBC solutions incorporate AI/ML to predict call failures, recommend configurations, or automate threat responses.
• Centralized Orchestration and Policy Control: Enterprises seek unified platforms to manage policy enforcement, call routing, and session prioritization across multiple SBC instances or locations.
• Support for Emergency Services (e.g., E911): SBCs are increasingly required to support location-aware emergency calling capabilities in compliance with regional laws (such as Kari’s Law and Ray Baum’s Act in the U.S.).
• Call Recording and Retention: Compliance mandates in finance, healthcare, and government sectors are pushing for SBC features that support lawful intercept and long-term call logging.
• STIR/SHAKEN Implementation: In North America, SBCs are often involved in implementing STIR/SHAKEN frameworks to combat robocalls by authenticating caller IDs.
• Integration with CPaaS and UCaaS Platforms: SBCs are now being designed to work seamlessly with communications platforms like Twilio, RingCentral, and Zoom Phone.
• API Exposure and Programmability: Modern SBCs expose APIs for dynamic call routing, security policy updates, and integration into DevOps pipelines.
• Self-Healing Capabilities: SBCs are beginning to adopt AI-based automation for detecting and resolving issues autonomously.
• Dynamic Traffic Shaping: AI helps in optimizing voice traffic routing based on real-time network conditions, enhancing call quality and resource utilization.

How To Choose the Right Session Border Controller

Selecting the right Session Border Controllers is a critical decision for organizations that manage voice over IP (VoIP) communications. SBCs play a vital role in securing and managing real-time communication sessions such as VoIP, video, and messaging. The process begins by assessing your organization’s specific needs, including the volume of concurrent sessions, the types of media streams, and the geographic distribution of your communication infrastructure.

Understanding the network environment is essential. If your organization operates in a highly complex network or integrates with multiple service providers, you need an SBC that offers advanced interoperability features and can seamlessly bridge different signaling protocols like SIP. Security requirements are another major consideration. A strong SBC should offer protection against threats such as denial-of-service attacks, toll fraud, and eavesdropping. It should also support encryption standards such as TLS and SRTP to ensure the confidentiality and integrity of voice and video streams.

Performance and scalability are important for growing businesses. It’s important to choose an SBC that not only meets your current traffic demands but also allows for easy scaling as your needs evolve. Look for solutions that offer high availability and redundancy features to ensure uninterrupted service during failures or maintenance.

Compatibility with existing infrastructure is another key factor. The SBC must integrate well with your current PBX systems, unified communication platforms, and carrier services. It should also support any necessary codecs and media transcoding to enable smooth communication across diverse systems.

Management and monitoring capabilities should not be overlooked. An ideal SBC provides an intuitive user interface, detailed logging, real-time monitoring, and analytics tools that help network administrators maintain control and quickly troubleshoot issues.

Lastly, consider the vendor’s reputation, support services, and long-term roadmap. Choosing a vendor with a solid track record and robust customer support ensures that your investment remains secure and aligned with future technological developments.

In summary, selecting the right SBC involves a thorough understanding of your communication needs, security posture, scalability goals, and existing network environment, coupled with an evaluation of vendor reliability and support.

Utilize the tools given on this page to examine session border controllers in terms of price, features, integrations, user reviews, and more.