Businesses are steadily moving away from traditional PBX systems towards Unified Communications platforms that bring voice, video, messaging, conferencing, and collaboration together. Microsoft Teams, Zoom, Cisco Webex, and SIP-based UCaaS platforms are increasingly becoming central to everyday business communication.

For IT teams, however, moving from traditional telephony to Unified Communications is rarely a simple replacement exercise. Existing phone numbers, SIP trunks, legacy PBX systems, call routing, recording, security policies, and PSTN connectivity still need to work throughout the transition.

Session Border Controller as a Service, or SBC as a Service, provides the secure connection between these different communication environments. Instead of deploying and maintaining SBC hardware at every location, organisations can use a managed SBC service to connect their existing telephony infrastructure with cloud-based Unified Communications platforms.

This gives IT teams a practical way to migrate communications in phases while maintaining security, interoperability, and service availability.

What is SBC as a Service?

A Session Border Controller sits at the edge of a voice network and manages communication sessions between different networks, platforms, and service providers. SBC as a Service provides these capabilities through a managed service, so businesses don’t have to purchase, configure, and maintain dedicated SBC infrastructure.

It can connect SIP trunks, PSTN services, legacy PBX systems, IP telephony infrastructure, and cloud UC platforms while controlling how voice and other real-time communications move between them.

For organisations moving towards Unified Communications, this creates an important bridge between existing infrastructure and new cloud platforms.

The Role of SBC as a Service

Interoperability
One of the biggest challenges during a UC migration is getting different systems to communicate correctly.

Existing environments may use different signalling protocols, codecs, PBX platforms, and service providers. SBC helps manage these differences through signalling normalisation, protocol interworking, and media transcoding where required.

This lets organisations keep using existing telephony infrastructure while introducing new UC platforms in stages.

Security
Moving voice communications onto IP networks introduces security considerations that traditional closed telephony environments may not have faced. SBC provides a controlled boundary between internal communication systems and external networks.

Security capabilities can include signalling and media encryption, authentication, access controls, topology hiding, traffic filtering, and protection against communication-based attacks.

These controls become particularly important when voice services connect to public networks, cloud platforms, and multiple service providers.

Consistent Call Quality
Voice and video communications are highly sensitive to latency, packet loss, and network congestion.

SBC can apply call admission control, bandwidth management, media handling, and Quality of Service policies to help maintain reliable communication sessions. This becomes increasingly important for organisations with distributed offices, remote employees, and multiple cloud environments.

Intelligent Call Routing
SBC can route calls based on predefined business policies, destinations, availability, and network conditions.
Calls can be directed between different SIP trunks, UC platforms, PBX systems, and service providers. This provides greater flexibility while supporting resilience and business continuity.

Flexible Deployment
Not every organisation moves to the cloud at the same pace. Some businesses may retain their existing PBX while introducing Microsoft Teams calling for selected departments. Others may operate a combination of cloud and on-premises communications for an extended period.

SBC as a Service supports these hybrid environments and lets businesses migrate based on operational requirements rather than replacing everything at once.

How SBC as a Service Supports Unified Communications Migration

Connecting Legacy and Cloud Systems
Many organisations have invested significantly in existing PBX infrastructure and cannot simply switch it off when adopting Unified Communications. SBC allows legacy PBX systems, SIP trunks, PSTN connectivity, and cloud UC platforms to coexist.

Employees can move to the new platform in stages while other departments or locations continue using the existing system. This phased approach reduces disruption and gives IT teams greater control over the migration.

Supporting Microsoft Teams Direct Routing
For organisations adopting Microsoft Teams as their communications platform, SBC can support Direct Routing and enable Teams users to make and receive external PSTN calls. Businesses can retain existing carrier relationships and telephone numbers while bringing calling capabilities into Microsoft Teams.

This is particularly useful for organisations with multiple branches or more complex telephony requirements.

Migrating from a Legacy PBX with SBC as a Service

A successful migration requires careful planning rather than an immediate switch from one platform to another.

1. Audit the Existing Environment
Begin by documenting the current telephony infrastructure. This should include telephone numbers, extensions, call flows, devices, SIP trunks, analogue endpoints, voicemail, call recording, CRM integrations, and other dependencies. The network should also be assessed to determine whether it can support IP voice and real-time UC traffic reliably.

2. Select the UC Platform and SBC Service
Choose the Unified Communications platform that best suits the organisation’s requirements, and confirm it interoperates with the selected SBC service. Consider capacity, security, compliance, scalability, support, existing carrier relationships, and integration with legacy infrastructure.

3. Plan a Phased Migration
Moving users or locations in stages can significantly reduce operational risk. The existing PBX and new UC platform can operate simultaneously while users are migrated gradually. Number porting, SIP trunk changes, voicemail, auto attendants, call queues, and routing policies should all form part of the migration plan.

4. Configure the SBC Environment
The SBC is configured between the UC platform, existing PBX environment, and PSTN or SIP provider. Security policies, routing rules, SIP connectivity, Direct Routing, and compliance requirements can then be applied according to the organisation’s communication architecture.

5. Test Before Cutover
Testing should cover inbound and outbound calls, internal extensions, number presentation, emergency calling where applicable, call transfers, failover, voicemail, call recording, and interoperability between old and new systems. Testing different failure scenarios is equally important.

6. Validate Performance
Voice quality, latency, reliability, and application functionality should be monitored closely. Problems identified during this stage can be addressed before larger groups of users are migrated.

7. Prepare Users
Employees need to understand how to use new UC applications, softphones, headsets, call transfer functions, voicemail, conferencing, and other communication features. User preparation can significantly affect how successfully the new platform is adopted.

8. Cut Over and Optimise
Final cutover should be scheduled to minimise disruption. IT teams should continue monitoring call quality, SBC performance, routing, and user feedback after migration. Configurations can then be adjusted as communication requirements change.

Why SBC as a Service Makes Sense for IT Teams

Managing an SBC internally requires infrastructure, technical expertise, maintenance, software updates, security management, and ongoing monitoring. SBC as a Service shifts much of this responsibility to a managed service provider.

This reduces the infrastructure IT teams need to maintain while providing a scalable way to support changing communication requirements.

It also allows organisations to add users, locations, SIP connections, or cloud communication services without deploying additional SBC hardware at every site.

Frequently Asked Questions

Why is SBC as a Service important during a UC migration?
SBC provides secure connectivity between legacy PBX systems, PSTN services, SIP trunks, and cloud UC platforms. It helps organisations maintain existing communication services while gradually moving users and locations to a new platform.

What migration challenges can SBC as a Service address?
SBC can help address interoperability between different systems, SIP trunk connectivity, PSTN integration, security, call routing, media compatibility, and coexistence between legacy and cloud environments.

Is SBC as a Service suitable for hybrid environments?
Yes. Hybrid deployment is one of its strongest use cases. Businesses can operate legacy PBX systems alongside cloud UC platforms and migrate users at a pace that suits their operational requirements.

Viva Digitally SBC as a Service
Viva Digitally SBC as a Service helps organisations securely connect VoIP networks, SIP services, PSTN connectivity, existing telephony infrastructure, and modern Unified Communications platforms.

For IT organisations moving from traditional telephony to platforms such as Microsoft Teams and other cloud-based communication environments, the service provides a managed approach to interoperability, security, call routing, and migration. Instead of replacing the entire communications environment at once, businesses can transition in stages while maintaining the systems and services they still depend on. With Viva Digitally SBC as a Service, organisations can simplify their move to Unified Communications while maintaining secure, reliable business communication throughout the transition.
Contact Viva Digitally to schedule a demo and discuss your Unified Communications requirements.