A session border controller (SBC) is a network device, physical or virtual, that sits at the border between two VoIP networks and controls how SIP calls and media cross it. It secures, normalises and routes voice traffic between your phone system and the outside world. We design, supply, configure and support certified SBCs for SIP trunk security, Microsoft Teams Direct Routing and connecting different PBX platforms.
What is a session border controller?
An SBC does four jobs: security (hiding your internal network and blocking SIP attacks), interoperability (translating between SIP dialects), media handling (codec transcoding and NAT traversal) and routing (directing calls and enforcing policies such as call admission control). In short, it is the firewall, translator and traffic controller for voice over IP.
Why UK businesses need an SBC
- SIP trunk security: exposing a PBX directly to a SIP trunk risks toll fraud, denial of service and eavesdropping.
- Microsoft Teams Direct Routing: Microsoft requires a certified SBC. See Teams calling in the UK.
- Interoperability: lets a legacy PBX, a new IP PBX, SIP trunks and Teams work together during and after an ISDN migration.
- Toll-fraud protection: call admission control and rate limiting cap exposure if credentials are compromised.
SBC platforms we deploy
| Platform | Type | Best for |
|---|---|---|
| anynode (TE-SYSTEMS) | Software | Teams Direct Routing, flexible virtual deployments |
| AudioCodes | Hardware & virtual | Teams-certified Mediant SBCs, enterprise SIP trunking |
| Ribbon | Hardware & virtual | Carrier-grade and large enterprise deployments |
| Oracle (Acme Packet) | Hardware & virtual | High-capacity environments |
| Wildix / Sangoma | Built-in SBC layer | Deployments where the PBX provides SBC functions |
Hardware or software SBC?
A hardware SBC is a purpose-built appliance with predictable capacity, ideal where physical separation and high call volumes matter. A software SBC runs on a standard server or virtual machine, scales by licence and suits cloud, hybrid and Teams deployments. We recommend the right model for your call volumes, security posture and deployment.
Our SBC service
- Assessment: your PBX, SIP trunks, Teams estate and security requirements.
- Design and sizing: platform and licence tier for your concurrent calls and redundancy, including high-availability pairs.
- Configuration: SIP normalisation, transcoding, security policies, routing and Teams Direct Routing.
- Testing and go-live: inbound and outbound tests, failover checks and number-porting confirmation.
- Support: monitoring, firmware updates and managed support.
Frequently asked questions
What does a session border controller do?
An SBC secures, translates and routes SIP voice traffic at the edge of a network. It protects the PBX from SIP attacks and toll fraud, translates between incompatible SIP implementations, transcodes audio codecs, handles NAT traversal and enforces call-routing and admission-control policies.
Do I need an SBC for Microsoft Teams Direct Routing?
Yes. Direct Routing requires a Microsoft-certified SBC between Teams and your SIP trunk. Calling Plans and Operator Connect do not need your own SBC.
What is the difference between an SBC and a firewall?
A standard firewall inspects general data traffic but does not understand SIP and RTP voice protocols. An SBC is built for real-time communications. It understands SIP signalling and media, prevents voice-specific attacks and protects call quality.
Can an SBC be virtual?
Yes. Software SBCs such as anynode run on a virtual machine or standard server and scale by licence, which suits cloud, hybrid and Teams deployments.
Need an SBC for your business?
UK phone: +44 (0)20 4602 3181 | Email: info@netontechnologies.com
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