A session border controller, or SBC, is yet another way to ensure VoIP security. It’s a piece of hardware that lives at the dividing line between networks. Functionally, it acts as gatekeeper, security detail, and manager all rolled into one. Read on to find out how they work.
What Is a Session Border Controller?
A session border controller, or SBC, has many roles and can seem dauntingly technical at first glance, but it’s much simpler when you break it down one word at a time.
“Session” is another term for a VoIP call. You may remember that VoIP runs on the signaling protocol SIP, or “session initiation protocol.” SIP is related to the “controller” part, but we’ll get there in a bit.
“Border” refers to the hardware’s placement at the boundary of separate networks. We know, we know, we often talk about how the Internet is borderless in terms of geopolitics or connecting people, but it does have its own borders. It’s sort of like a firewall. While a firewall protects your home network from the rest of the Internet, SBCs are sort of like that for VoIP (however, it’s certainly not a replacement). This is the gatekeeper part of session border control.
“Controller” refers to the security and management duties. Think of it like a bodyguard-slash-executive-assistant for each session. SBCs have quite a bit of influence over SIP call flow and the data that make up sessions. To call anyone outside your network with VoIP, you must connect to their network plus their VoIP service provider’s network. SBCs allow you to do that by securely managing data traffic during the call, making sure only the right data streams come and go through your network.
Session Border Control and Security
You can never have enough VoIP security. Normally, it’s a smart move to have as few ports open to your network as possible. But voice and video calls require more open ports, which means more access points for hackers and malicious software. It’s why you should use a VPN when on an unsecured network – and SBCs are able to navigate VPNs to allow calls through. Just like firewalls, this hardware provides additional border security for VoIP calls. They sit at the demarcation point between one network and another, monitoring the data streams that want to come and go so that nothing bad sneaks into your network during calls.
Session Border Controllers and Call Management
While security is the main attraction, session border controllers do quite a bit more. They offer quality of service, connectivity, performance stats, billing info, and more.
Quality of Service and Prioritization
SBCs help enhance VoIP call quality by managing data dispatch to minimize lag and jitter. They monitor traffic to properly allocate resources, prevent VoIP fraud, and prioritize emergency calls.
Connectivity
Connecting a VoIP call requires a good amount of SIP requests and translation. SBC hardware can handle NAT (network address translation) traversal, protocol translations, VPN connectivity, and internet protocol interworking.
Statistics and Billing
Naturally, any call that passes through your network border (i.e., not an in-house call to a colleague) will have billing info and call statistics. So it makes sense that this VoIP hardware device can collect this data as it passes through for further usage and analysis.
To put it lightly, session border controllers do some heavy lifting. They’re even able to support DTMF (dual-tone multi-frequency) tones and fax technology to keep your legacy equipment functional longer than usual. And of course, extra VoIP security is always a good idea.