What is a Session Border Controller (SBC)?


We don’t need to tell you that the COVID-19 pandemic changed the way businesses do business forever- you already know that. Unified communications was a leading reason organizations were able to thrive while working from home. 

Practically overnight, team members needed the ability to collaborate, message, video conference and call customers all from home. And organizations found unified communication systems provided an immediate, affordable, one-stop-shop for managing telecommunications. That’s why it’s no surprise that the UC market grew more than 29% from 2019 to 2020. 

But working in remote environments posed two big issues for organizations: (1) How do you connect all your tools in one place at an affordable rate and (2) how do you do so securely? They found that answer in a little piece of hardware called a Session Border Control (SBC).

Thinking about investing in an SBC for your business? It’s a hefty investment… so you’ll likely want to know the ins and outs before making the jump. We’re here to help. Read on to learn what a session border control is and the key benefits it delivers for your organization. 

Defining a Session Border Controller

To start with the basics, a session border controller is a hardware device activated at the connection between your PBX and PSTN to manage communication data between the two networks. It keeps your VoIP network secure while resolving different signals and media flows from end devices so that a unified exchange can happen between two or more callers.

If you’re managing a call center, an easy way to think of an SBC is the piece of hardware that seamlessly connects your telephony provider and UC platform to allow your customers to get connected to the right agents quickly. 

If you’ve landed on this blog, it’s likely because you’ve found that for some UC platforms such as Microsoft Teams Direct Routing requires you to have your own SBC, or work with a licenced partner who has one. You’re also probably quickly discovering that SBCs aren’t cheap. So is it worth installing your own… or should you pay a monthly fee to work with a partner? We help you answer those questions below.  

How Does a Session Border Controller Work?

An SBC is a traffic manager, data carrier and security guard all in one device. It directs incoming calls to the right recipient and outgoing calls to the correct regional telephone carrier and destination. If your organization’s phone system employs session initiation protocol (SIP), a session border controller will use that open protocol to open, maintain, and close out phone calls (including video calls) between your PBX and PSTN.

SBCs normalize SIP communications signaling and data streams coming in and going out so that calls can take place. You could think of an SBC as the gate agent at a customs station that inspects all incoming and outgoing traffic as well as the baggage everyone carries with them.

The benefit of using SIP trunking with an SBC is that your company will likely not have to replace any standard SIP phones to ensure compatibility with a new UC. If you’re looking into Microsoft Teams specifically, it ensures that any SBC it certifies is compatible with major manufacturers’ existing handset models.

3 Key Benefits of Using a Session Border Controller

Now that we’ve covered the jargon, let’s dive into the perks of having an SBC. There are several benefits to installing a session border controller for your business’s phone network, but the main three are quality of service, security, and reliability.

    1. Quality of Service

An SBC is a data carrier. If you record a call, an SBC will help manage the audio and visual data that flows into your UC platform from the person on the other end, and vice versa. SBCs help shorten the path media files take to reach an end user which results in calls that are more clear, with less lag time.

An SBC will help your IT admins monitor the quality of each call connection in real-time to ensure the connection quality allows for clear, lag-free conversations. They enhance the fault tolerance of your phone system by increasing the redundancies of your phone units without taking up unnecessary bandwidth. If one component of your phone system fails, an SBC will automatically redirect traffic around that failed element so the system can continue operating.

    1. Security

SBCs are security guards for your UC and internal phone network. Because it operates on the edge between the PSTN and your PBX, SBCs are the devices that allow or prohibit calls between your business and the outside world. SBCs moderate the streams of data flowing in and out of your phone network by controlling port activity. It will allow authorized calls and data to pass through while blocking threats. This helps prevent deceitful, potentially expensive activity such as toll fraud.

Like a firewall, your SBC will only allow authorized calls or sessions to happen. With your phone admins’ policies programmed into it, SBCs can prevent unwanted call traffic from making its way to your team and wasting their time. The gatekeeper role of an SBC further secures your phone system by preventing denial of service (DoS), distributed denial of service (DDoS) and spam over IP telephony (SPIT) attacks.

    1. Reliability

Your IT admins can program an SBC to adhere to any data policies so that the SBC can efficiently monitor communication traffic and manage data pathways in real-time. SBCs analyze call traffic and optimize where to route it to maximize the bandwidth in use at any given time. This results in fewer dropped calls. They can prioritize emergency calls and redirect sessions as needed. SBCs can support multiple devices across a network, and help ensure the interoperability of your VoIP devices.

The Modern Way to Connect Your Business Phone Network

Adopting a unified communications platform can be a complex task involving hundreds, if not thousands, of devices that “speak” different tech languages and operate with different policies. A session border controller unifies all those devices and ensures they operate harmoniously so that your business can operate its phone network seamlessly. The added benefits of enhanced quality of service, security and reliability that a session border controller provides makes an SBC an essential part of any modern business phone network.

At AVOXI, we’ve recently developed our own integration, connecting those who use MS Teams Direct Routing with our global voice platform. Learn more about how you can access two-way voice services across more than 170+ countries.